	ACADEMIC COMPUTING and COMMUNICATIONS CENTER

IBM HELP Glossary of CMS and Computer Related Terms

ABSTRACT
GLOSSARY
-- Purpose
-- Notice

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ABSTRACT

This document is a glossary of computer terms with emphasis on VM and CMS related terms. It is part of the VM/ESA CMS 9 online HELP system (it is available through the HELP LIBRARY TASK menu), and is copyright by IBM.

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GLOSSARY

Purpose

This glossary contains technical terms that refer to the components, functions, operation, and use of VM/ESA Release 2 and related products. You can find additional information on IBM terminology in the Dictionary of Computing, SC20-1699.

Notice

Some entries in this glossary that are from the Dictionary of Computing include definitions from:

The American National Standard Dictionary for Information Systems, ANSI X3.172-1990, copyright 1990 by the American National Standards Institute (ANSI). Copies may be purchased from the American National Standards Institute, 11 West 42nd Street, New York, New York 10036. Definitions are identified by the symbol (A) after the definition.
The Information Technology Vocabulary, developed by Subcommittee 1, Joint Technical Committee 1, of the International Organization for Standardization and the International Electrotechnical Commission (ISO/IEC JTC1/SC1). Definitions of published parts of this vocabulary are identified by the symbol (I) after the definition; definitions taken from draft international standards, committee drafts, and working papers being developed by ISO/IEC JTC1/SC1 are identified by the symbol (T) after the definition, indicating that final agreement has not yet been reached among the participating National Bodies of SC1.

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A-type address constant: In assembler language, an address constant used for branching within a module or for getting data.
abend: (1) Abnormal end of task. (2) Synonym for abnormal termination.
abend dump: The contents of main storage, or part of main storage, written to an external medium for debugging an error condition that resulted in the termination of a task before its regular completion.
abnormal end of task (abend): Termination of a task before its completion because of an error condition that cannot be resolved by recovery facilities while the task is executing.
abnormal termination: The ending of processing before planned termination. Synonymous with abend.
accept: Allowing a connection to the user's virtual machine from another virtual machine or from the user's own virtual machine.
access list: A list of address spaces that are available to a program operating in access-register mode. For XC virtual machines, access lists are managed by CP and are formally called host access lists. See also host access list.
access method services (AMS): The utility that allocates and configures VSAM data sets. AMS is invoked through the AMSERV command in CMS.
access mode: A method VM/ESA uses to control user access to data files. Access modes let the user read and write data to a file, or only read data from a file. See file mode.
access register: A 32-bit register that contains an ALET identifying an address space to be used for data references when in access-register mode. ESA/370, ESA/390, and ESA/XC architectures provide 16 access registers, numbered 0-15. When in access-register mode, a "B" field (or sometimes an "R" field) in an instruction designates both the general register to be used as a base register and the access register to be used to specify the address space containing the data.
access security: Information that a target LU and target transaction program use to verify whether a source program is authorized to make a connection. This information consists of a user ID and, possibly, a password.
access-list entry (ALE): Synonym for host access-list entry.
access-list-entry token (ALET): A 32-bit value that is an indirect specification of an address space. When a program is operating in access-register mode, an ALET contained in an access register designates the address space containing an instruction operand.
access-register (AR) mode: An address translation mode in which the contents of the access registers are used to determine the address space containing a storage operand. The SET ADDRESS SPACE CONTROL instruction can be used to change the PSW to enter and exit access-register mode. See also primary-space mode.
ACF/SSP: Advanced Communications Function for Systems Support Programs.
ACF/VTAM: Advanced Communications Function for Virtual Telecommunications Access Method.
active record: A record added or appended to a file currently in use.
active work unit: A work unit that has uncommitted work associated with it. A request was made on the work unit (other than an atomic request) and no commit or rollback has occurred.
ACU: Automatic calling unit.
ADCON: An A-type address constant used in calculating storage addresses.
address space: A collection of bytes that are allocated, and in many ways managed, as a single entity by CP. Each byte within an address space is identified by a unique address. An address space represents an extent of storage available to a program. Address spaces allocated by VM range in size from 64KB to 2GB.
address stop: See breakpoint and instruction address stop.
address-space-identification token (ASIT): An 8-byte token that uniquely identifies a particular address space allocated by CP. The ASIT is a system-wide, unique identification token--once an ASIT value has been assigned to an address space, that ASIT value is not used again within the scope of a VM/ESA system IPL (CP IPL).
addressing-capability exception: A program exception that arises as a result of an attempt to access an address space for which access permission has been revoked by the owner of the address space.
Advanced Communications Function for Systems Support Programs (ACF/SSP): An IBM licensed program made up of a collection of utilities and small programs. SSP is required for operation of the NCP.
Advanced Communications Function for Virtual Telecommunications Access
Method (ACF/VTAM): An IBM licensed program that controls communications and flow of data in an SNA network. It provides single-domain, multiple-domain, and interconnected network capability.
advanced function printer (AFP): An all-points-addressable printer, such as the IBM 3800-3 and IBM 3820 printers, capable of printing images and text.
advanced function printing data stream (AFPDS): A method of representing image data in a file that is destined for printing on a PSF-controlled printer.
Advanced Interactive Executive for PS/2 (AIX PS/2): An IBM licensed program that contains the features of AIX PS/2 Version 1.2.
Advanced Program-to-Program Communications (APPC): The inter-program communication service within SNA LU 6.2 on which the APPC/VM interface is based.
Advanced Program-to-Program Communications/VM (APPC/VM): An API for communicating between two virtual machines that is mappable to the SNA LU 6.2 APPC interface and based on IUCV functions. Along with the TASK virtual machine, AVS virtual machine, and VTAM, APPC/VM provides this communication within a single system, throughout a collection of systems, and throughout an SNA network.
AFP: Advanced function printer.
AFPDS: Advanced function printing data stream.
agent: (1) In CRR sync point processing, the role of the CRR sync point manager (SPM) when sync point requests are received from an initiator that is a partner in a protected conversation. (2) A task for an SFS file pool server or CRR recovery server. The SFS file pool server and CRR recovery server provide support for multitasking several agents.
AIX domain controller: (1) An AIX application that lets programs on AIX workstations communicate with resources on VM systems or other programmable workstations in a CS collection. (2) See also AIX PS/2 domain controller, OS/2 domain controller, VM/ESA domain controller.
AIX PS/2: Advanced Interactive Executive for PS/2.
AIX PS/2 domain controller: An AIX PS/2 application that lets user programs on AIX workstations running VM PWSCS connect to and communicate with resources on VM/ESA and OS/2 Extended Edition systems using ISFC or VM PWSCS through a channel-attached OS/2 domain controller running VM PWSCS.
AL: ANSI-labeled tape without user-label processing.
ALE: Access-list entry.
ALET: Access-list-entry token.
alias: A pointer to an SFS base file. An alias can be in the same directory as the base file or in a different directory. There must always be a base file for the alias to point to. The alias references the same data as the base file. Data is not moved or duplicated.
allocation tree: A conceptual structure showing the nodes that are allocating protected conversations within a CRR coordinated transaction.
alphanumeric: A character set that contains letters, digits, and usually other characters, such as punctuation marks.
alternate console: A console assigned as a backup unit to the system console.
alternate path support: The selection of a path to a device from any of the available paths, even though the primary path is busy. The selection is made in response to an I/O request for a device, through use of the two-channel switch, the two-channel switch additional features, and the string switch hardware feature.
alternating operating systems: Multiple operating systems loaded consecutively into a virtual machine. Information is passed between the operating systems by the CP spooling facilities. Synonymous with flip-flop.
American National Standard Code for Information Interchange (ASCII): The standard code, using a coded character set consisting of 7-bit coded characters (8 bits including parity check), used for information interchange among data processing systems, data communication systems, and associated equipment. The ASCII set consists of control characters and graphic characters.
AMS: Access method services.
anchor block: The CMS anchor block is an area in user storage that contains space for 16 anchor slots. It also includes space for the register save area used by the Anchor facility. The anchor block storage persists after an abend occurs.
anchor identifier: The anchor identifier uniquely identifies the program when calling the CMS Anchor facility. The ANCHOR macro accepts an anchor identifier 3 bytes in length and is padded on the right with a blank. The anchor identifier must be assigned by IBM.
anchor slot: Each anchor slot is 8 bytes in length. The first 4 bytes contain the anchor identifier. The second 4 bytes contain the anchor word. They are both initially zero.
anchor word: The anchor word contains the user's data and is usually the address of the caller's data area.
annotated flow diagram: A diagram consisting of logic labels and commentary. It describes the general flow and use of CP logic modules and their relationships to other modules while doing a specific function or task.
ANSI: American National Standards Institute.
ANSI Version 3: Term that refers to the ANSI standards, ANSI X3.27-1978, level 4.
AP: Attached processor.
AP/MP mode: A mode of VM/ESA while running in an AP or MP system.
APAR: Authorized program analysis report.
APAR number: The number that IBM assigns to an APAR and to the change resulting from it.
API: Application program interface.
APPC: Advanced Program-to-Program Communications.
APPC link: A logical TSAF link that is physically controlled by VTAM, and is established using the TSAF VTAM line driver.
APPC/VM: Advanced Program-to-Program Communications/VM.
APPC/VM VTAM Support (AVS): A component of VM/ESA that lets application programs using APPC/VM or CPI Communications communicate with programs anywhere in a network defined by IBM's SNA. AVS transforms APPC/VM into APPC/VTAM protocol.
application program: A program written for or by a user that applies to the user's work, such as a program that does inventory control or payroll.
application program interface (API): The formally defined programming language interface between an IBM system component or licensed program and its user.
apply: When servicing a product or component, to generate an auxiliary control structure from a PTF. See apply disk, apply ID, apply message log, apply list, apply status table, apply string.
apply disk: In VMSES/E, a minidisk or SFS directory containing the files that describe the maintenance levels: the apply status table, AUX files, version vector tables, the select data file, and the build status table.
apply ID: A 1- to 8-character, alphanumeric identifier that is used to name the software inventory files created during apply processing. The user can change this value to define different maintenance levels.
apply list: A file listing PTFs applied to a product or component.
apply message log: A file in which the VMFAPPLY EXEC writes status and error messages during apply processing.
apply status table: The software inventory table that identifies what PTFs have been applied to the product. The system level of the table identifies what product or component has been applied to the system. The file type of the system level inventory table is SYSAPPS and the file type of the service level inventory table is SRVAPPS.
apply string: In VMSES/E, the set of apply disks.
AR: Access register.
architected segment: A 1MB portion of real storage defined by the 370-XA, ESA/370, ESA/390, and ESA/XC architectures.
AR mode: Access-register mode.
area: A term acceptable for DASD space when there is no need to differentiate between space on count-key-data devices and FB-512 devices. See DASD space.
ASCII: American National Standard Code for Information Interchange.
ASIT: Address-space-identification token.
ASP: Asymmetric multiprocessing system.
assembler language: A source language that includes symbolic machine language statements in which there is a one-to-one correspondence with instruction formats and data formats of the computer.
asymmetric multiprocessing system (ASP): An extension to the IBM System/360 Operating System that provides increased automation of computer operations for large-scale data processing installations.
asynchronous communication: A method of communication in a conversation that lets a program issue functions on other conversations while waiting for a particular function to complete.
atomic request: An SFS command or program function (CSL routine) that completes execution immediately and does not affect work in other resources (such as other SFS file pools) on the work unit. Any file pool updates caused by an atomic request are committed (or rolled back) when the file pool server finishes processing the request. Atomic requests cannot be issued to a file pool that has uncommitted work for the specified (or default) work unit.
attached processor (AP): A processor that has no I/O capability and is always linked to the processor initialized for I/O handling.
attached processor operation: A mode in which VM/ESA runs tasks on two processors, only one of which has attached channels; however, the tasks come from a common dispatch queue and share common storage.
attachment interface: The logical interconnection and interaction between or to software programs that enable the programs to function together.
attention interrupt: An I/O interrupt caused by a terminal user pressing the attention key (or equivalent). See attention key (ATTN key) and signaling attention.
attention key (ATTN key): A function key on terminals that, when pressed, causes an I/O interruption in the processing unit. See signaling attention.
attention symbol: Under CP, for printing terminals only, the character (always the exclamation point (!) character) that indicates each time the attention key is pressed.
ATTN key: Attention key.
AUL: ANSI labeled tape with user label processing.
authority: In SFS, the permission to access a file or directory. You can have read authority or write authority (which includes read authority). You can also have file pool administration authority, which is the highest level of authority in a file pool.
authorized application: A GCS application, started with the OSRUN command, that operates in supervisor state, and can use privileged functions. Contrast with ordinary application.
authorized program: Synonym for privileged program.
authorized program analysis report (APAR): An official request to the responsible IBM Change Team to look into a suspected problem with IBM code or documentation. APARs describe problems giving conditions of failure, error messages, abend codes, or other identifiers. They also contain a problem summary and resolution when applicable. See program temporary fix (PTF).
authorized user ID: In GCS, a user ID that provides access to the GCS supervisor, supervisor state, and (at times) certain restricted CP commands. This access is provided by including the user ID on a list of authorized user IDs compiled with the GCS GROUP EXEC. The virtual machine associated with an authorized user ID is an authorized machine, and programs running in that machine are authorized applications.
authorized virtual machine: A GCS virtual machine identified by user ID.
automatic calling unit (ACU): A device that receives dial digits from the communications adapter and is associated with the switched line modem, enabling the modem to call its counterpart at the remote system.
automatic logon: A process by which an operator's or user's virtual machine is initiated by someone other than the user of that virtual machine. For example, the primary VM/ESA system operator's virtual machine is automatically started during VM/ESA initialization. A privileged user can enter the AUTOLOG command to start some other (disconnected) virtual machine.
automatic software re-IPL: The process by which the control program attempts to restart the system after abnormal termination. This process does not involve the hardware IPL process. See virtual=real machine recovery.
AUX file: Auxiliary control file.
auxiliary control file (AUX file): A file that contains a list of file types of update files applied to a particular source file or to control the service level used during build. See control file and preferred auxiliary file. Synonymous with auxiliary file.
auxiliary directory: In CMS, an extension of the CMS file directory for a minidisk, which contains the names and locations of certain CMS modules not included in the minidisk's CMS minidisk file directory.
auxiliary file: Synonym for auxiliary control file.
auxiliary storage: Data storage other than main storage; in VM/ESA, auxiliary storage is usually a direct access device.
AVS: APPC/VM VTAM Support.
AVS virtual machine: The virtual machine that manages a gateway that allows APPC communication between VM systems and an SNA network.

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The verb form of "backout" is "back out."

base disk: In VMSES/E, minidisk or SFS directory containing the original product files as shipped on the product tape.
base file: The first occurrence of an SFS file. It remains the base for the life of the file, even if the file has been renamed. Aliases point to base files. See base file type.
base file type: In VMSES/E, the file type used for a serviceable part when there is no service. The PTF number in the file type is set to "00000." For example, EXC00000 is the base file type for an exec.
base string: IN VMSES/E, the set of base disks.
basic control (BC) mode: A mode in which additional System/370 features, such as new machine instructions, are not operational. Contrast with extended control (EC) mode.
basic conversation: A conversation where data is sent in APPC-defined logical record formats. Programs must be coded to consider the amount of data sent. Contrast with mapped conversation.
basic sequential access method (BSAM): An access method for storing or getting data blocks in a continuous sequence (using either a sequential access or direct access device).
BC mode: Basic control mode.
BDT: Bulk data transfer. See MVS/Bulk Data Transfer.
binary digit: Either of the digits 0 or 1 when used in the pure binary numeration system. Synonymous with bit.
binary synchronous communication (BSC): Communication using binary synchronous line discipline in which transmission of binary-coded data between stations is synchronized by timing signals generated at the sending and receiving stations.
bit: (1) Either of the binary digits 0 or 1. See byte. (2) Synonym for binary digit.
block: (1) A unit of DASD space on FB-512 devices. For example, FB-512 devices can be the IBM 9335, 9332, 9313, 3370, and 3310 DASD using fixed-block architecture. (2) In CMS Multitasking, to stop the execution of a thread until a function has been completed or a condition is satisfied.
block extent: A continuous space on a direct access storage volume that does not have to be stored contiguously with a block (4096) of pages.
blocked file: A file in which each data block may contain one or more records. If a file is unblocked, each data block contains only one record.
bootstrap program: A technique or device that brings itself into a desired state by its own action. For example, a machine routine whose first few instructions are sufficient to bring the rest of itself into the computer from an input device.
border: A boundary around a window. The user can enter one-letter BORDER commands from the corners of the border. For example, the letter P entered from a border corner pops the window. The border corners are indicated by a + (plus) sign.
box: In CP, to shut off all communication with an I/O device because CP has identified a serious problem with the device, for example, exceeding the hot I/O rate.
bpi: Bits per inch.
Bpi: Bytes per inch.
break tree processing: The process of breaking off other parts of a sync point tree to ensure that a unique LUWID is used by each sync point tree after a protected conversation abnormally ends.
breakpoint: A place in a program, specified by a command or a condition, where the system halts execution and gives control to the workstation user or to a specified user.
broadcast message: Information that can be sent by the system operator to all terminal users that are enabled to receive messages. The three major classes of messages are: (1) log (LOGMSG) messages automatically displayed at the user's terminal when the user logs on, (2) optional lower priority log messages, and (3) informational warning messages that alert users to some imminent event or action.
BSAM: Basic sequential access method.
BSC: Binary synchronous communication.
buffer: An area of storage, temporarily reserved for performing input or output, from which data is read, or into which data is written. See forms control buffer (FCB), spool file buffer linkage block, terminal input buffer.
build: (1) In the installation and service of a product, to do the necessary steps to produce executable code or systems. This is often called the build process. (2) See build disk, build message log, build ID, build list, build status table, build string.
build disk: In VMSES/E, a minidisk or SFS directory where executable versions of objects serviced are built.
build ID: A 1- to 8-character, alphanumeric identifier that is used to name the software inventory files created during build processing. The user can change this value to define different maintenance levels.
build list: An exec that names the serviceable parts included in an object being built, and parameters and options used to build the object.
build message log: A file in which the VMFBLD EXEC writes status and error messages during build processing.
build status table: The software inventory table that identifies what products have been built, in the system level, and what individual objects have been generated for the product, in the service level. The file type of the system level inventory table is SYSBLDS and the file type of the service level inventory table is SRVBLDS.
build string: The set of build disks.
built-in function: A specialized function, invoked by a keyword, that has been built into the system program code because it is commonly required by many users.
built-in stage command: A stage command supplied by CMS Pipelines. See also user-written stage command.
byte: A unit of storage, consisting of eight adjacent binary digits that are operated on as a unit and constitute the smallest addressable unit in the system.
B1: One of several security designations that can be assigned to a computing system by the U. S. Department of Defense. The B1 designation indicates that the system:

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cache fast-write: A 3990 Model 3 function where data is written directly to cache without using nonvolatile storage and the data is available for later destaging. This function should be used for data of a temporary nature, or data that is readily repeated.
callable services library (CSL): A package of CMS assembler routines that can be stored as an entity and made available to a high-level language, REXX, or an assembler program.
cascaded agent: An agent whose initiator is an agent of another initiator. In this role, an agent is responsible for responding to sync point requests from its cascaded initiator.
cascaded initiator: An agent that has protected conversations with cascaded agents. The cascaded initiator takes the role of initiator in relation to its agents and is responsible for propagating sync point requests to its cascaded agents.
catalog storage group: The storage group in a file pool that contains information about the objects (such as files and directories) and authorizations that exist in the file pool. See file pool catalog.
CAW: Channel address word.
CC: Condition code.
CCH: Channel-check handler.
CCS: Console communication service.
CCT: Communications control table.
CCW: Channel command word.
CE: (1) Channel end. (2) Correctable error. (3) (IBM) Customer Engineer.
Central Processing Complex (CPC): The boundaries of a system exclusive of I/O control units and devices, that can be controlled by a single operating system. A CPC consists of main storage, one or more central processing units, time-of-day clocks, and channels, which are or can be placed in a single configuration. A CPC also includes channel subsystems, service processors, and expanded storage.
central site/system: The main installation with skilled system support personnel such as system programmers and operations staff.
CETI: Continuously Executing Transfer Interface.
CF: Crypto Facility.
chain link record: In CMS, a record that contains pointers to the physical blocks currently assigned to a CMS file.
changes: In installation and service, service supplied by IBM and original equipment manufacturers (OEMs) for their programs. In the IBM service process, there are many ways users can receive information they need to fix (change) a portion(s) of a product they are running on a VM system. These include PTFs, APARs, user modifications, and information received over the phone. All these types of information are called changes.
channel: A path in a system that connects a processor and main storage with an I/O device.
channel address word (CAW): An area in storage that specifies the location in main storage at which a channel program begins.
channel command word (CCW): A doubleword at the location in main storage specified by the channel address word. One or more CCWs make up the channel program that directs data channel operations.
channel status word (CSW): An area in storage that provides information about the termination of I/O.
channel-check handler (CCH): In System/370, a feature that records information about channel errors and issues appropriate messages to the operator.
channel-set switching: A facility used in some attached processor environments. It lets processing continue in uniprocessor mode on the attached processor after the main processor enters a disabled WAIT state following an irrecoverable error (a hard machine or channel check), or after the system operator varies the main processor offline. CP switches all active channels on the main processor to the attached processor, and processing continues in uniprocessor mode.
channel-to-channel (CTC) device: A hardware device that connects two channels on the same computing system or on different systems. CTC devices include both CTCAs and 3088 MCCUs.
channel-to-channel adapter (CTCA): A hardware device that connects two channels on the same computing system or on different systems.
character delete symbol: Synonym for logical character delete symbol.
checkpoint: An internal file pool server operation during which the changes recorded on the log minidisks are permanently made to the file pool.
checkpoint (CKPT) start: A VM/ESA system restart that attempts to recover information about closed spool files previously stored on the checkpoint cylinders. The spool file chains are reconstructed, but the original sequence of spool files is lost. Unlike warm start, CP accounting and system message information is also lost. Contrast with cold start, force start, and warm start.
circumventive service: Information that IBM supplies over the telephone or on a tape to circumvent a problem by disabling a failing function until a PTF is available as a corrective service fix. See patch and zap.
CKD: Count-key-data.
CKPT start: Checkpoint start.
class A user: See primary system operator privilege class.
class Any user: Any user, regardless of class, who is allowed to use a subset of CP commands to log onto VM/ESA, have the terminal logically connected to a multiple-access virtual machine, or send messages to the operator or to other users.
class authority: Privilege assigned to a virtual machine user in the user's directory entry; each class specified allows access to a subset of all the CP commands. See privilege class and user class restructure (UCR).
class B user: See system resource operator privilege class.
class C user: See system programmer privilege class.
class D user: See spooling operator privilege class.
class E user: See system analyst privilege class.
class F user: See service representative privilege class.
class G user: See general user privilege class.
class override file: A file containing control statements defining changes in the privilege classes of CP commands and diagnose codes. The override program uses this file to establish a new class structure of commands under UCR.
clock comparator: A hardware feature (required by VM/ESA) that causes an interruption when the TOD clock has equaled or exceeded the value specified by a program or virtual machine.
CLP: Current line pointer.
CMR: Conversation management routine.
CMS: Conversational Monitor System.
CMS batch facility: A facility that lets the user run time-consuming or noninteractive CMS jobs in another CMS virtual machine dedicated to that purpose, thus freeing the user's own terminal and virtual machine for other work.
CMS blip facility: An indication to the user at a terminal, by way of a tilt/rotate of the IBM Selectric type ball (if using a printing terminal), or the display of one or more specified characters, every 2 seconds of either real or virtual execution time that has elapsed for the CMS virtual machine. Whether the time shown is real or virtual depends on the current setting of the REALTIMER option.
CMS editor: A CMS facility that lets the user create, change, insert, delete, or rearrange lines of data in a CMS file. See edit mode and input mode.
CMS EXEC: An EXEC procedure or EDIT macro written in the CMS EXEC language and processed by the CMS EXEC processor. Synonymous with CMS program.
CMS EXEC language: A general-purpose, high-level programming language, particularly suitable for EXEC procedures and EDIT macros. The CMS EXEC processor executes procedures and macros (programs) written in this language. Contrast with EXEC 2 language and Restructured Extended Executor (REXX) language.
CMS EXEC processor: The component of the VM/ESA operating system that interprets and executes procedures and EDIT macros written in the CMS EXEC language.
CMS file system: A way to create files in the CMS system. CMS files are created by using an identifier consisting of three fields: file name, file type, and file mode or SFS directory. These files are unique to the CMS system, cannot be read or written using other operating systems, and are stored either on minidisks or SFS directories.
CMS files: Refers exclusively to files in the fixed-block format used by the CMS file system. VSAM and OS data sets and DOS files are not compatible with the CMS file format and cannot be manipulated using CMS file system commands.
CMS loader work file: The CMS file loaded into storage by the LOAD command.
CMS minidisk file directory: A directory on each CMS disk that contains the name, format, size, and location of each of the CMS files on that disk. When a disk is accessed by the ACCESS command, its directory is read into virtual storage and identified with any letter from A through Z. Synonymous with master file directory block and minidisk directory.
CMS nucleus: The portion of CMS that is resident in the user's virtual storage whenever CMS is executing. Each CMS user receives a copy of the CMS nucleus when the user IPLs CMS. See saved system and shared segment.
CMS Pipelines: A part of CMS that processes pipelines and includes stage commands that can be used in a pipeline.
CMS program: Synonym for CMS EXEC.
CMS system disk: The virtual disk (file mode S) that contains the CMS nucleus and the disk-resident CMS commands. The CMS system disk can have extensions; usually as file mode Y.
CMS system file: Any file residing on the CMS system disk instead of on a user's disk or in a user's file space.
CMS system minidisk: The minidisk located at virtual address 190. It contains the system commands for which the user has read-only access.
CMS user disk: One or more virtual disks that contain CMS or read-only DOS or OS files that can be accessed by the user. If the user has read/write access to a disk, the user can create programs and data files on the disk. Files are retained until the user deletes them. The user can also link to and access other users' disks, usually on a read-only basis.
CMS-formatted disk: A formatted disk used specifically with the CMS file system. It does not contain a VTOC and is incompatible with OS and DOS formatted disks. OS and DOS access methods cannot be directly used with CMS formatted disks.
CMS/DOS: The functions of CMS that become available when the user enters the command SET DOS ON. CMS/DOS is a part of the regular CMS system and is not a separate system. Users who do not use CMS/DOS are sometimes called OS users, because they use the OS simulation functions of CMS. Synonymous with DOS simulation under CMS. Contrast with OS simulation under CMS.
CMS/DOS phase library: Synonym for DOSLIB library.
CMSDOS: The standard name of the CMS/DOS saved segment. See saved segment.
CMSSERV: A command that starts a CMS router in the Enhanced Connectivity Facilities environment of VM/ESA.
CNTRL file: Control file with file type CNTRL.
cold start: A VM/ESA system restart that ignores previous data areas and accounting information in main storage, and the contents of paging and spool files on CP-owned disks. Contrast with checkpoint (CKPT) start, force start, and warm start.
collection: See TSAF collection or CS collection.
command: A request from a user at a terminal for the execution of a particular CP, CMS, GCS, TSAF, Dump Viewing Facility, or AVS function. A CMS command can also be the name of a CMS file with a file type of EXEC or MODULE. See subcommand and user-written CMS command.
command abbreviation: A short form of the command name, operand, or option that is not a truncation of the word. For example, MSG instead of MESSAGE, RDR instead of READER. Contrast with truncation.
command line: The line at the bottom of display panels that lets a user enter commands or panel selections. It is prefixed by an arrow (====>).
command privilege class: See privilege class.
command scan: In CMS, a routine that scans the command line entered and converts it to a standard CMS parameter list. See parameter list (PLIST).
commit: (1) In the context of SFS, to change a resource (such as a file) permanently. (2) In the context of CRR, to make permanent changes to protected resources (such as SFS file pools) during a transaction (CRR logical unit of work). CRR commits changes made by an application program or transaction program.
commit level: In CMS Pipelines, an indication of a stage's progress. The commit level determines when a stage is dispatched relative to other stages and is used to report to other stages that an error has been detected.
common dump receiver: One user ID in a virtual machine group appointed to receive other group members' storage dumps. Unless the user specifies otherwise, all dumped information automatically goes to this user ID (identified with the GCS GROUP EXEC). It should be an authorized user ID to receive fetch-protected data and storage with a key other than 14.
common lock: A doubleword in storage, controlled by the GCS LOCKWD macro. When a program is using common storage, it can turn the common lock ON. Other programs that examine the lock and find it ON cannot gain access to common storage.
Common Programming Interface (CPI): Provides languages, commands, and calls that allow the development of applications that are more easily integrated and moved across environments supported by SAA. VM/ESA supports the communications and the resource recovery elements of the CPI.
Common Programming Interface (CPI) Communications: A set of program-to-program communication routines that let applications written in REXX and high-level languages access APPC/VM functions. These routines are part of IBM's SAA and are also known as the SAA communications interface.
Common Programming Interface (CPI) Resource Recovery: See SAA Resource Recovery Interface.
common storage: A shared segment of reentrant code that contains free storage space, the GCS supervisor, control blocks, and data that all members of a virtual machine group share.
communication adapter: A program or a part of a program that handles communications with other programs. See SFS communication adapter.
communication link: Synonym for data link.
communication services (CS) collection: A group of one or more domains made up of VM systems or LAN-based workstations.
communications directory: A CMS facility that lets APPC/VM applications connect to a resource using symbolic destination names and special NAMES files.
communications partner: The virtual machine on the other end of the local APPC/VM path, not necessarily the target of the communications.
communications scanner: A communications controller hardware unit that provides the connection between lines and the central control unit. The communications scanner monitors telecommunication lines and data links for service requests.
communications server: A virtual machine that provides APPC/VM services between systems within a TSAF collection, and allows for communication between an APPC/VM environment and an SNA-defined network. TSAF and AVS are communication servers. See intermediate communications server.
compare states: The function of conveying the state of the CRR logical unit of work to a participating resource manager, and conveying the state of the protected resource's logical unit of work, including heuristic actions, back to the CRR recovery server.
compile: To translate a program written in a high-level programming language into a machine language program.
component: A collection of objects that together form a separate functional unit. A product may contain many components. For example, CP, CMS, and TSAF are components of VM/ESA.
component override: Synonym for component parameter override.
component override area: An area of the product parameter file or of a product parameter override file that contains one or more component parameter overrides. Synonymous with override area.
component parameter override: A component parameter, defined in a component override area, that updates or replaces a component parameter defined in a component area of the product parameter file. Synonymous with component override and override.
concurrently: Concerning a mode of operation that includes doing work on two or more activities within a given (short) interval of time.
condition code (CC): A code that reflects the result of a previous I/O, arithmetic, or logical operation.
condition variable: In an application using CMS multitasking services, a variable whose value indicates a state of a mutex-protected shared resource. This state, or condition, is defined by the application. It can be waited on and signaled as being true.
connect: Establishing a path to communicate with another virtual machine or with the user's own virtual machine.
connected: In CMS Pipelines, pertaining to a stream that is attached to a stream from another stage, so that data can flow from one stage to another. If streams are not connected, then data cannot flow from one stage to another.
connectivity program request block (CPRB): An interface control block that requesters and servers use to communicate information.
connector: In CMS Pipelines, a symbol that connects the input or output stream of a stage to the beginning or end of a pipeline specified on a CALLPIPE or ADDPIPE pipeline subcommand called by the stage. The minimal connector is an asterisk and a colon (*:).
console: A device used for communications between the operator or maintenance engineer and the computer.
console communication service (CCS): A group of CP modules that interfaces with the VTAM service machine, providing full VM/ESA console capabilities for SNA terminal users.
console function: The subset of CP commands that lets the user simulate almost all of the functions available to an operator at a real system console.
console spooling: Synonym for virtual console spooling.
console stack: Refers collectively to the program stack and the terminal input buffer.
contention: The situation where two LUs try to allocate a conversation over the same session at the same time.
context editing: A method of editing a file without using line numbers. To refer to or change a particular line or a group of lines; all or part of the contents of that line are specified.
Continuously Executing Transfer Interface (CETI): An interface that uses continuously executing channel programs to transfer messages between two systems, or between an application and a control unit.
control block: A storage area that a computer program uses to hold control information.
control data: In a file pool, the data that controls the DASD space and objects within a file pool. Control data consists of the POOLDEF file, the control minidisk, and all minidisks allocated to storage group 1.
control file: (1) In service, a file with file type CNTRL that contains records that identify the updates to be applied and the macro libraries, if any, needed to assemble that source program. (2) A CMS file that is interpreted and directs the flow of a certain process through specific steps. For example, the control file could contain installation steps, default addresses, and PTF prerequisite lists and many other necessary items.
control minidisk: In a file pool, the minidisk that tracks the physical DASD blocks allocated to the file pool.
control processing complex (CPC): One or more processors, main storage, or channels, where the processors can be configured to share main storage.
control program: A computer program that schedules and supervises the program execution in a computer system. See Control Program (CP).
Control Program (CP): A component of VM/ESA that manages the resources of a single computer so multiple computing systems appear to exist. Each of these apparent systems, or virtual machines, is the functional equivalent of an IBM System/370, 370-XA, or ESA computer. Also, XC virtual machines provide functions beyond the ESA architecture. See also virtual machine.
control register: A register used for operating system control of relocation, priority interruption, program event recording, error recovery, and masking operations.
control section (CSECT): The part of a program specified by the programmer to be a relocatable unit, all elements of which are loaded into adjoining main storage.
control statement: A statement that controls or affects program execution in a data processing system.
control terminal: Any terminal currently controlling system resources and used by the primary system operator (privilege class A), the resource operator (privilege class B) or the spooling operator (privilege class D).
control unit: A device that controls I/O operations at one or more devices.
control unit terminal (CUT): An operational mode that allows one logical terminal session. Contrast with distributed function terminal (DFT).
conversation: A connection between two transaction programs over an LU-LU session that lets them communicate with each other while processing some transaction. The programs establish a conversation, send and receive data in the conversation, and then terminate the conversation.
conversation characteristics: The attributes of a conversation that determine the functions and capabilities of programs within the conversation.
conversation correlator: A value that identifies an APPC conversation and is unique at the LU that generates it. The conversation correlator is established when the APPC conversation is established.
conversation management routine (CMR): A routine that resides in the GCS load library and controls the routing of inbound connections through AVS to available service pool virtual machines.
conversation partner: One of the two programs involved in a conversation.
conversation state: See program state.
Conversational Monitor System (CMS): A virtual machine operating system and component of VM/ESA that provides general interactive time sharing, problem solving, program development capabilities, and operates only under the control of the VM Control Program (CP).
Coordinated Resource Recovery (CRR): A CMS facility that implements the LU 6.2 sync point architecture, which ensures that transactions can update multiple protected resources with integrity. This means that all updates, within the transaction, are either completed (committed) or not completed (rolled back or backed out). CRR consists of the coordination function (see synchronization point processing), the resynchronization function (see resynchronization), and the logging function (see log minidisks). The coordination function resides in the application program's virtual machine. The resynchronization and logging functions reside in the CRR recovery server.
coordinated transaction: See logical unit of work (in terms of CRR) or see LUWID.
coordinated update: See logical unit of work (in terms of CRR) or see LUWID.
copy file: A file having file type COPY that contains nonexecutable real storage definitions that are referred to by macros and assemble files.
copy function: The function initiated by a PF key to copy the contents of a display screen onto an associated hardcopy printer. A remote display terminal copies the entire contents of the screen onto a printer attached to the same control unit. A local display terminal copies all information from the screen, except the screen status information, onto any printer attached to any local display control unit.
COR: Corrective service tape.
corequisite change: A change that must be applied to the user's product along with another change. For example, if the user needs to apply change1 to the system and change1 has a corequisite of change2, then the user must apply both change1 and change2 to the system, but not in a specific order. A corequisite change corrects a problem that requires changes to one or more elements of a product or component.
corrective service: Service that IBM supplies on tape to correct a specific problem.
corrective service tape (COR): A tape, supplied by IBM at the user's request, containing a fix for a specific problem and any requisites for the fix.
count-key-data (CKD) device: A DASD that stores data in the format: count field, usually followed by a key field, followed by the actual data of a record. The count field contains the cylinder number, head number, record number, and the length of the data. The key field contains the record's key (search argument).
CP: Control Program.
CP assist: A hardware function, available only on a processor with ECPS, that reduces CP overhead by doing the most frequently used tasks of CP routines.
CP command: A command available to all VM users. Class G CP commands let the general user reconfigure their virtual machine, control devices attached to their virtual machine, do input and output spooling functions, and simulate many other functions of a real computer console. Other CP commands let system operators, system programmers, system analysts, and service representatives manage the resources of the system.
CP directory: Synonym for VM directory.
CP privilege class: See privilege class.
CP read: The condition when CP is waiting for a response or request for work from the user. On a typewriter terminal, the keyboard is unlocked; on a display terminal, the screen status area indicates CP READ.
CP READ screen status: For a display terminal used as a virtual console under VM/ESA, an indicator located in the lower right of the screen, that indicates CP is waiting for a response or request for work from the user.
CP system disks: Any disk space CP uses, other than the CP paging, spooling, and temporary disk space; for example, virtual disks.
CP trace table: A table VM/ESA uses for debugging. Its size is a multiple of 4096 bytes and depends on the size of real storage or a user-specified value. This table contains the chronological occurrences of events that take place in the real machine, recorded in a wraparound fashion within the trace table. Synonymous with trace table.
CP-accessed disk: Any CMS-formatted minidisk that is available to CP after installation.
CP-owned disk: Any disk formatted by the CP Format/Allocate program and designated as system-owned during system generation; for example, the CP system residence volume, or any disk that contains CP paging, spooling, saved systems, or temporary disk space.
CPC: Control processing complex.
CPI Communications: Common Programming Interface Communications.
CPI Resource Recovery: Common Programming Interface Resource Recovery.
CPRB: Connectivity program request block.
CPU timer: A hardware feature that measures elapsed processor time and causes an interruption when a previously specified amount of time has elapsed. The CPU timer is decremented when the processor is executing instructions, is in a WAIT state, and is executing program loading instructions, but not when the processor is in a stopped state. A virtual machine that uses the CPU timer must have the EC mode and REALTIMER options active.
critical section: In CMS Multitasking, a block of code that manipulates a shared resource, such as a data structure or device.
cross system extensions (CSE): An environment in which end users attached to a single system can participate with additional systems as though all participating systems were one complex.
cross system extensions exclusion list: A list of user IDs excluded from the cross system extensions environment.
cross system extensions protected volume: A cross system extensions (CSE) volume not participating in the CSE environment.
CRR: Coordinated Resource Recovery.
CRR recovery server: A virtual machine, which is generated during VM/ESA installation, that provides the CRR logging and resynchronization functions. Every processor must have only one CRR recovery server.
CRT: Cathode ray tube.
Crypto Facility (CF): A hardware feature that provides cryptographic capability.
cryptography: A method of protecting data in computer and communication systems from unauthorized disclosure and modification. It involves the process of transforming plain-text into cipher-text (encipherment) and the reverse process of turning cipher-text into plain-text (decipherment).
CS collection: See Communication Services collection.
CSE: Cross system extensions.
CSECT: Control section.
CSL: Callable services library.
CSL routine: An assembler program that resides in a CSL and that can be invoked from a high-level language, REXX, or an assembler program to do a specific function.
CSR: (IBM) Customer Service Representative.
CSW: Channel status word.
CTC: Channel-to-channel.
CTCA: Channel-to-channel adapter.
current line pointer (CLP): A pointer that indicates the line of a CMS file on which the CMS Editor or the XEDIT editor is currently working.
CUT: Control unit terminal.
CVT: Communications vector table.
cylinder: In a disk pack, the set of all tracks with the same nominal distance from the axis about which the disk pack rotates.
C2: One of several security designations that can be assigned to a computing system by the U. S. Department of Defense. The C2 designation indicates that the system:

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DAC: discretionary access control.
DASD: Direct access storage device.
DASD Dump Restore (DDR) program: A service program that copies all or part of a minidisk onto tape, loads the contents of a tape onto a minidisk, or sends data from a DASD or from tape to the virtual printer.
DASD space: (1) Area allocated to DASD units on CKD devices. (2) Area allocated to DASD units on FB-512 devices. Note that DASD space is synonymous with cylinder when there is no need to differentiate between CKD devices and FB-512 devices.
DAT: Dynamic address translation.
data control block (DCB): A control block access method routines use to store and retrieve data.
data link: The equipment and rules (protocols) used for sending and receiving data. Synonymous with communication link.
data space: Informal term for an additional address space created by CP at the request of a program running in an XC virtual machine. This term is usually used to refer to these additional address spaces because they can contain data (operands of instructions) but instructions cannot be executed from within them.
data stream: A set of logical records sent one after the other.
DBCS: Double-byte character set.
DCB: Data control block.
DCF: Document Composition Facility.
DCSS: Discontiguous saved segment.
DDP: Distributed data processing.
DDP logical operator: (1) The person who handles nonroutine (nonprogrammed) messages sent from the local systems' programmable operator. (2) The person who is logically responsible for DDP system operations. See distributed data processing (DDP).
DDP operator: (1) The person who handles nonroutine (nonprogrammed) messages sent from distributed systems' programmable operators. (2) The person who is logically responsible for the DDP network. See distributed data processing (DDP).
DDR program: DASD Dump Restore program.
deadline priority: A value that sorts a virtual machine into the eligible lists and the run lists. This value determines when users (virtual machines) get their next time slice. This value is calculated each time a user is dropped from a queue and is based on paging activity, processor usage, and the load on the system as well as on user priority.
dedicated channel: A channel attached to a virtual machine, for its sole use, so that CP can bypass translating the addresses of virtual devices.
dedicated device: An I/O device or line not being shared among users. The facility can be permanently assigned to a particular virtual machine by a VM/ESA directory entry, or temporarily attached by the resource operator to the user's virtual machine.
dedicated maintenance mode: In a file pool server machine, a mode of file pool server processing during which the file pool server machine has exclusive use of the file pool. The file pool is unavailable to other users. Contrast with multiple user mode.
default file attributes: In CMS, certain reserved file type names that cause the CMS editors (EDIT and XEDIT) to assume certain values for record length, tab setting, uppercase or lowercase setting, record sequence numbering, verification mode, fixed- or variable-length record type, truncation column, and other related record characteristics.
default operand: An operand that has a preset value if a value is not specified on the CP or CMS command line.
delimited string: In CMS Pipelines, a character string beginning and ending with a delimiter. See also null string.
delimiter: (1) A flag that separates and organizes items of data. Synonymous with separator. (2) A character used to indicate the beginning and end of a character string. (T) (3) A character that groups or separates words or values in a line of input. (4) In CMS Pipelines, a character used before and after a string of characters to define a delimited string. The delimiter cannot be blank and it must not occur within the string. Two adjacent delimiters represent a null string.
delta disk: In VMSES/E, a minidisk or SFS directory containing control files used for servicing. The control files can include: apply lists, exclude lists, PTF parts lists, auxiliary control files, update files, and text files.
delta string: In VMSES/E, the set of delta disks.
dependent PTF: A PTF that has another PTF as a prerequisite or corequisite.
derived file: A CMS file created from selected versions of elements. The build process creates the derived file. Some derived files can be provided by IBM on the PUT tapes. The customer installation can also create them.
description table: The software inventory table that contains the descriptive name for a product, in the system level, and APARs in the service level. The file type of the system level inventory table is SYSDESCT and the file type of the service level inventory table is SRVDESCT.
destage: The asynchronous writing of new or updated data from cache or nonvolatile storage to DASD. This method of writing data is used only for the fast-write function of the 3990 Model 3 Storage Control.
device: (1) A mechanical, electrical, or electronic contrivance with a specific purpose. (2) See channel-to-channel (CTC) device, count-key-data (CKD) device, dedicated device, device block, device driver, device support facilities, direct access storage device (DASD), display device, draining a unit record device, fixed-block architecture (FBA) device, primary paging device, spooling devices, unit record device, virtual spooling device.
device block: A storage area used by a computer program to hold device information.
device driver: In CMS Pipelines, a stage command that reads data from or writes data to I/O and storage devices, host environments (including CP, CMS, and XEDIT), and REXX and EXEC 2 variables. Contrast with filter.
device support facilities: A program for doing operations on disk volumes so that they can be accessed by IBM and user programs. Examples of these operations are initializing a disk volume and assigning an alternate track.
DFT: Distributed function terminal.
DIAGNOSE interface: A programming mechanism that lets any virtual machine, including CMS, directly communicate with CP by way of the DIAGNOSE instruction. Specific interface codes let a virtual machine more efficiently request specific CP services.
DIRCONTROL directory: Synonym for directory control directory.
direct access storage device (DASD): A storage device in which the access time is effectively independent of the location of the data.
directory: See auxiliary directory, CMS minidisk file directory, directory control directory, file control directory, SFS directory, or VM directory.
directory control directory: A type of SFS directory with functional characteristics like a minidisk's. A single access authority applies to the directory and all the files in the directory. When you access a directory control directory in read-only mode, you cannot see changes made until you release and reaccess the directory. When you access the directory in read/write mode, changes become available as they are made. Synonymous with DIRCONTROL directory. Contrast with file control directory.
directory identifier (dirid): A fully qualified directory name (in which the file pool ID and user ID can be allowed to default), a file mode letter, or plus (+) or minus (-) file mode syntax (used in commands).
directory name (dirname): A fully qualified directory name that can incorporate a period (.) to indicate the user's own top directory (used in commands).
dirid: Directory identifier.
dirname: Directory name.
disable: Synonym for lock, as applied to file spaces and storage groups in the CMS Shared File System.
disconnect mode: The mode of operation in which a virtual machine is executing without a physical line or terminal connected as an operator console. Any attempt to issue a read to the console causes the virtual machine to be logged off after 15 minutes have elapsed, unless the user logs on again within the 15-minute interval. Note that with the SCIF, a user can be disconnected from a primary virtual console but still have console communications through the console of the secondary user.
discontiguous saved segment (DCSS): A saved segment that begins and ends on a megabyte boundary and is not a segment space or a member of a segment space. A DCSS may contain logical saved segments. Contrast with segment space and member saved segment.
discretionary access control (DAC): A method of restricting access to data objects based upon authorizations granted to users or groups of users. Discretionary access control protects all system objects from unauthorized access. Normally, authorization to access an object is granted by its owner. Occasionally, it can be granted by someone else, such as a privileged administrator.
disk: A magnetic disk unit in the user's CMS virtual machine configuration. See virtual disk.
disk operating system (DOS): An operating system for computer systems that use disks and diskettes for auxiliary storage of programs and data.
Disk Operating System/Virtual Storage Extended (DOS/VSE): An operating system that is an extension of DOS/VS. A VSE system consists of: (a) licensed VSE/Advanced Functions support, and (b) any IBM-supplied and user-written programs required to meet the data processing needs of a user. VSE and the hardware it controls form a complete computing system.
dispatch: To allocate time on a processor to jobs or tasks that are ready for execution. (I) (A) See dispatch list, dispatch request queue, dispatch/scheduler favoring scheme.
dispatch list: See run list.
dispatch request queue: A queue of executable CP tasks, I/O tasks, and timer requests ready to be dispatched.
dispatch/scheduler favoring scheme: A set of criteria that the dispatcher and scheduler use to create a bias in favor of queue 1 (Q1) users. Q1 users are usually highly interactive users.
dispatcher: The program in CP that places virtual machines or CP tasks into execution. The dispatcher selects the next virtual machine to run and prepares the virtual machine for problem state execution.
dispatching: (1) In VM/ESA, the starting of virtual machine execution. (2) In CMS Multi-tasking, giving each thread a turn at running on a processor. See dispatching class.
dispatching class: A set of threads with two properties:
display device: An I/O device that gives a visual representation of data.
display mode: A type of editing at a display terminal in which an entire screen of data is displayed at once and in which the user can access data through commands or by using a cursor. Contrast with line mode.
display paging: A technique used for scanning through a CMS file on a display terminal in display mode. When using the CMS Editor, scanning can include up to 20 lines at a time. When using the XEDIT editor, use the BACKWARD or FORWARD subcommands; if a number is not given with either subcommand, only one screen is shown.
display terminal: A terminal with a component that can display information on a viewing surface such as a screen or gas panel.
distributed data processing (DDP): Data processing in which processing, storage, and control functions, in addition to I/O operations, are distributed among remote locations and connected by transmission facilities.
distributed function terminal (DFT): An operational mode that allows multiple concurrent logical terminal sessions. Contrast with control unit terminal (CUT).
distributed logical operator: A virtual machine at the distributed system to which machine intervention requests are sent. A machine attendant mounts forms and tapes and turns the power ON or OFF for that site.
distributed processing: A transaction that involves more than one node to complete its processing. A node might be a VM/ESA virtual machine in the same processor or a different processor or it may be an LU partner in a non-VM system (for example, MVS). We can think of the use of SFS as distributed processing (a user machine and a server machine cooperating) and the file pool as a distributed resource.
distributed resources: See distributed processing.
distribution code: In the VM/ESA directory, a one- to eight-character identification word printed or punched with the user ID in the separator page (or punched card) to further identify the location or department of the user.
DMSPARMS file: A CMS file with a file type of DMSPARMS that contains the start-up parameters that SFS file pool server and CRR recovery server processing uses.
Document Composition Facility (DCF): A text processing program; its main component is the text formatter, called SCRIPT/VS. See SCRIPT/VS.
domain: A set of transaction programs and servers that allocate shared resources within a single logical system.
domain controller: A communications server that manages communications within a domain and between domains. See AIX domain controller, AIX PS/2 domain controller, OS/2 domain controler, VM/ESA domain controller.
domination rule: The rule defining when one security label dominates another:
dormant state: A state in which the active pages of a virtual machine have been paged out.
DOS: Disk operating system.
DOS simulation under CMS: Synonym for CMS/DOS.
DOS/VSE: Disk Operating System/Virtual Storage Extended.
DOSLIB library: A CMS library that contains the executable phases produced by the DOS Linkage Editor under CMS. These phases are equivalent to, but not usable in the DOS/VS core image library. These phases can be fetched and executed only under CMS/DOS. Synonymous with CMS/DOS phase library.
double key protection: This program support associates each 2KB block of real storage with two storage protect keys. Two keys are needed to protect a 4KB frame.
double-byte character set (DBCS): A character set that requires 2 bytes to uniquely define each character. This contrasts with EBCDIC, in which each printed character is represented by 1 byte.
double-density DASD volume: A DASD volume with twice the standard number of cylinders for its device type, for example, a 3380-E4 with 1770 cylinders, or a 3390-2 with 2226 cylinders. See single-density DASD volume and triple-density DASD volume.
DPA: Dynamic paging area.
drain: (1) For spooling devices: to bring spooling operations on a real device to a halt after the current spool file is processed. (2) For DASD: to bring input/output operations on a DASD to a halt after the present input/output operations are completed.
dual address space assist: Synonym for cross memory service.
dump: To write the contents of part or all of main storage, or part or all of a minidisk, to auxiliary storage or a printer. See abend dump.
Dump Viewing Facility: A component of VM/ESA that lets users display, format, and print data interactively from CP hard and soft abend, stand-alone, and virtual machine dumps; process CP trace table data stored on tape or in a system trace file; and display symptom records.
duplex pair: A logical volume comprised of two physical devices with all data recorded twice, once on each device. A 3990 Model 3 Storage Control automatically ensures that both devices are updated with each write operation to the dual copy volume.
dyadic processor: A processor complex containing two processors in one unit. Both processors share central storage, are controlled by a single operating system, directly communicate with each other, execute I/O operations through a common element, and can run with one central processor if the other is removed from the configuration because of an error. A dyadic processor cannot be configured into two independent uniprocessor units. Note that each processor has access to its own assigned channel set of up to 16 channels.
dynamic address translation (DAT): In System/370 and ESA virtual storage systems, the change of a virtual storage address to a real storage address during execution of an instruction.
dynamic configuration: Configuring a collection or reconfiguring a collection when a system enters or leaves the collection after a link goes up or down within the collection. See CS collection and TSAF collection.
dynamic paging area (DPA): An area of real storage that CP uses for virtual machine pages and pageable CP modules.
dynamically modified channel program: A channel program changed by the program or by data being read in from a channel during the interval between the execution of the START I/O (SIO) instruction and the channel end interruption.

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early warning system (EWS): An information system for getting information about programming problems to the field. The information includes:
EBCDIC: Extended binary-coded decimal interchange code.
EBT: Element build table.
EC level: Engineering change level.
EC mode: Extended control mode.
ECB: Event control block.
ECC: Error checking and correction.
ECF: Enhanced connectivity facilities.
ECKD: Extended count-key data.
ECPS:VM/370: Extended Control Program Support:VM/370.
ECSW: Extended channel status word.
EDF: Enhanced disk format.
edit: A function that makes changes, additions, or deletions to a file on a disk. These changes are interactively made. The edit function also generates information in a file that did not previously exist.
EDIT macro: (1) A procedure defined by a frequently used command sequence to do a commonly required editing function. A user creates the macro to save repetitious reentering of the sequence, and invokes the entire procedure by entering a command (that is, the macro file's file name). The procedure can consist of a long sequence of edit, CMS, and CP commands, along with EXEC 2 or CMS EXEC control statements to control processing within the procedure. (2) A CMS file whose file name starts with a dollar sign ($) character and whose file type is EXEC.
edit mode: The environment in which CMS EDIT subcommands and XEDIT subcommands can be entered by the user to insert, change, delete, or rearrange the contents of a CMS file. Contrast with input mode.
eligible list: The list of virtual machines waiting to get into the run list. They are runnable but cannot fit into the run list because of the current system load.
ELN: Exchange log names.
emulation: The use of programming techniques and special machine features to permit a computing system to execute programs written for another system.
emulation program (EP): A control program that lets an IBM 3704 or 3705 Communications Controller emulate the functions of an IBM 2701 Data Adapter Unit, an IBM 2702 Transmission Control Unit, or an IBM 2703 Transmission Control Unit.
enable: Deprecated term for removing a lock from an object in the CMS Shared File System, in particular from a file space or storage group.
end of file: In CMS Pipelines, a condition in which no data can flow through a stream because the stream has been severed.
enhanced connectivity facilities (ECF): A set of programs for interconnecting IBM Personal Computers and IBM System/370 host computers running the MVS/XA, VM/SP, VM/SP HPO, VM/XA SP, and VM/ESA operating systems.
enhanced disk format (EDF): A CMS file storage format that supports files consisting of 512-, 1K-, 2K-, or 4K-byte CMS blocks.
entry point: An address or label of an instruction performed on entering a computer program, a routine, or a subroutine. A program can have several different entry points, each corresponding to a different function or purpose.
environmental record editing and printing program (EREP): A program that makes the data contained in the system recorder file available for further analysis.
EOF: End of file.
EOV: End of volume. The logical end of a physical tape volume.
EP: Emulation program.
erased alias: An alias that no longer points to a base file because the base file was erased.
ERDS: Error recording data set.
EREP: Environmental record editing and printing program.
EREP file: A collection of error records produced by the malfunctioning of hardware components on a computer and stored for processing by the EREP program.
error checking and correction (ECC): In a processing unit, the detection and correction of all single-bit errors, plus the detection of double-bit and some multiple-bit errors.
error recording area: The DASD space that the system programmer defines during system generation on the system residence volume that CP uses to record formatted outboard error recordings, machine check records, and channel check records. For CKD devices, this area is between 2 and 9 contiguous cylinders in size; for FB-512 devices, the size of this area can be any number of contiguous pages.
error recording data sets (ERDS): A central processor repository for hardware error records.
ESA virtual machine: A virtual machine that simulates ESA/370 or ESA/390 functions. Contrast with 370 virtual machine, XA virtual machine, and XC virtual machine
ESA/XC: Enterprise Systems Architecture/Extended Configuration.
ESA/XC architecture: A virtual machine architecture in which DAT-off programs, like CMS and CMS applications, can create and access additional address spaces called data spaces. These additional address spaces can also be shared with programs running in other virtual machines. The ESA/XC virtual machine architecture is available only when VM/ESA is running on an ESA/390 processor.
escape symbol: Synonym for logical escape symbol.
escape to CP: Under VM/ESA, a transfer of control to CP when either the terminal user or the machine stops virtual machine operation. This can occur by entering a CP command (such as #CP), by invoking a DIAGNOSE function, or by signaling attention. See DIAGNOSE interface, signaling attention, and attention interrupt.
ESCM: ESCON Manager.
ESCON: Enterprise systems connection.
ESCON architecture: An architecture that uses fiber optic channels to interconnect computer systems.
ESCON directors: Dynamic switches that connect multiple control units and channels to implement the ESCON architecture. These switches are integral for the attachment of devices to both single and multiple systems.
ESCON Manager (ESCM): A licensed program that provides host control to help manage connections that use ESCON Directors.
Ethernet: See IEEE 802.3.
event: (1) An occurrence of significance to a task; for example, the completion of an asynchronous operation, such as an input/output operation. (2) In CMS Multitasking, an occurrence defined to be an event by CMS or an application. Such defined events can be monitored and signaled by CMS and by processes using CMS multitasking services. See event control block (ECB), event name, event signal, system event.
event control block (ECB): A control block that represents the status of an event.
event name: In applications using CMS multitasking services, a character string of arbitrary length and composition that is the primary identifier of an event.
event signal: In applications using CMS multitasking services, a signal that originates with CMS or an application to indicate that an event has occurred. The signal consists of the event name and additional data to be matched against keys specified by processes that want to monitor the event.
EWS: Early warning system.
exchange log names: An exchange of log data (log names, LU names, and TPN) for validating levels of log data between the CRR recovery server and participating resource managers, or between the CRR recovery server on one processor and another CRR recovery server on another processor.
exclude list: A file listing PTFs to be omitted from a product or component.
exclusive access: In addition to the data on the disk remaining unchanged by others, no one else has or can access the specified minidisk until the person holding the stable read or write releases access.
exclusive segment: A range of pages within a saved system, member saved segment, or discontiguous saved segment that can be accessed by only one virtual machine at a time.
EXEC procedure: (1) A procedure defined by a frequently used sequence of CMS and CP commands to do a commonly required function. A user creates the procedure to save repetitious reentering of the sequence, and invokes the entire procedure by entering a command (that is, the exec file's file name). The procedure could consist of a long sequence of CMS and CP commands, along with REXX, EXEC 2, or CMS EXEC control statements to control processing within the procedure. (2) A CMS file with a file type of EXEC.
EXEC 2 EXEC: Synonym for EXEC 2 program.
EXEC 2 language: A general-purpose, high-level programming language, particularly suitable for EXEC procedures and XEDIT macros. The EXEC 2 processor runs procedures and XEDIT macros (programs) written in this language. Contrast with CMS EXEC language and Restructured Extended Executor (REXX) language.
EXEC 2 processor: A program in VM/ESA that interprets and executes procedures, EDIT macros, and XEDIT macros written in the EXEC 2 language.
EXEC 2 program: An EXEC procedure, EDIT macro, or XEDIT macro written in the EXEC 2 language and processed by the EXEC 2 processor. Synonymous with EXEC 2 EXEC.
executable phase library: See DOSLIB library.
executable statement: In an EXEC procedure, EDIT macro, or XEDIT macro, any statement that the REXX Interpreter, the EXEC 2 processor, or the CMS EXEC processor processes. This can be a control statement or assignment, a CMS or CP command, or a null line.
exit: See user exit and installation-wide exit.
expanded storage: Optional integrated high-speed storage. Expanded Storage can be shared by CP and one or more virtual machines. It can also be dedicated to CP or to a particular virtual machine.
expanded virtual machine assist: A hardware assist function, available only on a processor that has ECPS, that handles many privileged instructions not handled by VMA, and extends the level of support of certain privileged instructions beyond that provided by VMA.
explicit lock: A lock on a file or directory that a user explicitly created by entering a CREATE LOCK command or executing a DMSCRLOC CSL routine.
extended binary-coded decimal interchange code (EBCDIC): A set of 256 characters, with each character represented by 8 bits.
extended communications: A set of program-to-program communication routines that are an extension to CPI-Communications routines. These routines are not part of IBM's Systems Application Architecture.
extended control (EC) mode: A mode in which all features of a System/370 computing system, including dynamic address translation, are operational. Contrast with basic control (BC) mode.
Extended Control Program Support (ECPS:VM/370): A hardware assist feature that improves the performance of CP by reducing CP overhead. ECPS:VM/370 consists of CP assist, expanded virtual machine assist, and virtual interval timer assist.
extended count-key data (ECKD) architecture: A storage architecture specifically designed to support nonsynchronous DASD control units.
extended PLIST (untokenized parameter list): Four addresses that indicate the extended form of a command as it was entered at a terminal.
external object: In SFS, an object within a file pool that an SFS server can refer to, but does not control. An external object contains a remote name of an entity residing outside the file pool. The external entity may be a file, but it can be something else.
external page storage: The portion of auxiliary storage that contains 4K-byte pages.
external page storage management: A set of routines in the paging supervisor that control the transfer of data between real storage and external page storage.
external security manager: A program that either augments or completely replaces the authorization checking done by file pool server processing.

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favored execution performance option: A virtual machine performance option that lets an installation force the system to allocate more of its resource to a given virtual machine than would usually be the case.
FB-512: An FBA device that stores data in 512-byte blocks (refers to DASD devices such as the IBM 9335, 9332, 9313, 3370, and 3310).
FBA: Fixed-block architecture.
FCB: (1) Forms control buffer. (2) Function control block. (3) File control block.
feature: A part of an IBM product that can be ordered separately by the customer.
fence: A logical boundary that separates one or more paths or elements from the remainder of the logical DASD subsystem. This separation allows isolation of failing components so that they do not affect normal operations.
fetch protection: A storage protection feature that determines right-of-access to main storage by matching the protection key associated with a main storage fetch reference with the storage keys associated with those frames of main storage.
field-developed program: An IBM licensed program that does a function for the user. It can interact with IBM licensed programs, or it can be a stand-alone program.
FIFO (first-in-first-out): A queuing technique in which the next item to be retrieved is the item that has been on the queue for the longest time. Contrast with LIFO (last-in-first-out).
file access mode: A file mode number that designates whether the file can be used as a read-only or read/write file by a user. See also file mode.
file control block: A control block used by OS Simulation to contain information about an I/O device or file, such as: name, device type, format, and I/O control data.
file control directory: A type of SFS directory for which separate access authorities are granted to the directory and to the individual files in the directory. When you access a file control directory, changes to the directory become available as they are made. Synonymous with FILECONTROL directory. Contrast with directory control directory.
file definition: (1) Equating a CMS file identifier (file name, file type, file mode) with an OS data set name by the FILEDEF command; or equating a DOS file ID with a CMS file identifier by the DLBL command. (2) Identifying--by way of either the FILEDEF or DLBL commands--the input or output files used during execution of an OS or DOS simulation program.
file ID: A CMS file identifier that consists of a file name, file type, file mode, or directory ID. The file ID is associated with a particular file when the file is created, defined, or renamed under CMS. See file name, file type, and file mode.
file mode: (1) A two-character CMS file identifier containing the file mode letter (A through Z) followed by the file mode number (0 through 6). The file mode letter indicates the minidisk or SFS directory on which the file resides. The file mode number indicates the access mode of the file.
file name: A one-to-eight character alphanumeric field, containing A through Z, 0 through 9, and special characters $ # @ + - (hyphen) : (colon) _ (underscore), that is part of the CMS file identifier and serves to identify the file for the user.
file pool: A collection of minidisks managed by SFS. It contains user files and directories and associated control information. Many users' files and directories can be contained in a single file pool.
file pool administration machine: A virtual machine with file pool administration authority.
file pool catalog: The part of a file pool that contains information about the objects stored in the file pool and the authorizations granted on those objects. See catalog storage group.
file pool ID: The name of a file pool. It is part of a fully-qualified directory name, identifying where the directory and all files in it are located. It has up to eight characters, followed by a colon (:).
file pool server machine: A virtual machine that is properly configured to manage a file pool. (Its VM/ESA system directory entries must, for example, contain the MDISK statements for a file pool.)
file space: A user's allocation of space within a file pool.
file status table (FST): A table that describes the attributes of a file on a CMS disk, including file name, file type, file mode, date last written, and other status information.
file system command: A CMS command that creates or manipulates CMS files.
file system control block (FSCB): A collection of information about a CMS file, which CMS OS simulation commands and user programs use. A file system control block is established for a file by the FILEDEF command or the FSCB macro instruction.
file tag: A character string associated with a VM/ESA spool file that contains information about that spool file.
file type: A one-to-eight character alphanumeric field, containing A through Z, 0 through 9, and special characters $ # @ + - (hyphen) : (colon) _ (underscore), that is used as a descriptor or as a qualifier of the file name field in the CMS file identifier. See reserved file types.
file type abbreviation table: The software inventory table that identifies the mapping between PTF-numbered file types and the real CMS file type. The service level inventory does not contain this table.
FILECONTROL directory: Synonym for file control directory.
filter: In CMS Pipelines, a stage command that transforms data but does not move data into or out of the pipeline. Contrast with device driver. See filter package.
filter package: In CMS Pipelines, a MODULE file that contains stage commands.
first-level storage: Refers to real main storage. Contrast with second-level storage and third-level storage.
fixed-block architecture (FBA) device: A disk storage device that stores data in blocks of fixed size or records; these blocks are addressed by block number relative to the beginning of the particular file.
flat file: A file that consists of a set of records ordered by record number or as sequentially entered in the file; a two dimensional file.
flip-flop: Synonym for alternating operating system.
floating-point register: A register that can manipulate data in a floating-point representation system.
flush list: A set of pages available to replenish the free list.
FMH5: Function Management Header 5.
force start: A VM/ESA system restart that attempts to recover information about closed spool files previously stored on the checkpoint cylinders. All unreadable or incorrect spool file information is ignored. Contrast with checkpoint (CKPT) start, cold start, and warm start.
format program: (1) In CMS, the service program that creates 1024-, 2048-, or 4096- byte blocks on a minidisk, counts or redefines the number of cylinders on a virtual disk, or creates a DASD label for the virtual disk. (2) In CP, the service program that formats (in 4096-byte blocks), allocates, and creates DASD labels for CP-owned disks for paging, spooling, and CP system residence. Contrast with virtual disk initialization program.
forms control buffer (FCB): In the 3800 Printing Subsystem, a buffer for controlling the vertical format of printed output. The FCB is analogous to the punched-paper, carriage-control tape that IBM 1403 Printers use.
forward recovery: The capability of a resource to recover all the data in the event of a media failure, including updates to the data that have been made since the last backup of the data.
free list: A list maintained by CP that points to a set of pages that can be allocated to satisfy both virtual machine and system page requests.
free storage: Storage not allocated. The blocks of central storage available for temporary use by programs or by the system.
FSCB: File system control block.
FST: File status table.
full recording mode: The mode of operation where transient processor and main storage errors that are corrected or circumvented by hardware retry or error correction code logic, are then recorded on the VM/ESA error recording cylinders.
full-pack minidisk: A virtual disk that contains all of the addressable cylinders of a real DASD volume.
full-screen CMS: When a user enters the command SET FULLSCREEN ON, CMS is in a window and can take advantage of 3270-type architecture and windowing support, and various classes of output are routed to a set of default windows. Also, users can type commands anywhere on the physical screen and scroll through commands and responses previously displayed. See windowing.
full-screen editor: An editor used at a display terminal where an entire screen of data is displayed at once and where the user can access the data through commands or by using a cursor. See full-screen CMS.
full-screen mode: In VM, the environment in which an entire 3270 display screen is under the control of a program running in a virtual machine.
fully-qualified LU name: A name that identifies each LU in an SNA network. It consists of a network ID followed by a network LU name. Contrast with locally-known LU name.
function control block (FCB): In Subsystem Support Services (SSS), a control block that contains information such as a function's status, event control block, task I/O queue, and I/O queue.
Function Management Header 5 (FMH5): A field at the beginning of an application request that carries control information for the target LU in an SNA network.

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GAM/SP: Graphics Access Method/System Product.
gateway: The LU name of a VM system, CS, or TSAF collection that is a source for communications to an SNA-defined network or the target of communications from an SNA-defined network.
gateway manager: A virtual machine in which one or more gateways are active. AVS is a gateway manager.
GB: gigabyte.
GCS: Group Control System for ESA/370 or ESA/390 architecture.
GDDM: Graphical data display manager.
general register: In CMS, a register that does operations such as binary addition, subtraction, multiplication, and division. General registers primarily compute and modify addresses in a program.
general user privilege class: The subset of CP commands that lets the Class G user manipulate and control a virtual machine.
generic file ID: A file identifier that allows the use of asterisks. The asterisk replaces any string of characters when the system is searching for a match on the rest of the file identifier.
gigabyte (GB): 1,073,741,824 bytes.
global gateway: (1) A gateway that programs outside a CS or TSAF collection can use to access global resources inside the collection. (2) A gateway that global resource manager programs use to access resources outside a CS or TSAF collection. Contrast with private gateway and system gateway.
global resource: A resource accessible from anywhere within a CS or TSAF collection and whose identity is known throughout the collection. A shared file system file pool is an example of a global resource. Contrast with local resource, private resource, and system resource.
global resource manager: (1) An application that runs in a server virtual machine and identifies itself to the CS or TSAF collection as a global resource owner using *IDENT. Contrast with local resource manager, private resource manager, and system resource manager. (2) An application that runs in a server workstation and identifies itself to its domain controller as a global resource owner.
global system lock: A defer lock that provides system integrity for AP and MP support of command processing and code executed by IOBLOCK, TRQBLOK, or CPEXBLOK.
GOS: Guest operating system.
GPR: General-purpose register.
graphical data display manager (GDDM): (1) A group of routines that let pictures be defined and procedurally displayed through function routines that correspond to graphic primitives. Contrast with presentation graphics routines (PGR). (2) An IBM licensed program that creates page segments.
group: Synonym for virtual machine group.
group configuration file: A file that the GROUP EXEC creates. It contains the blueprint for building the user's virtual machine group. The name of the file is systemname GROUP, where systemname is the name of the user's GCS saved system.
Group Control System (GCS): A component of VM/ESA, consisting of a shared segment that the user can IPL and run in a virtual machine. It provides simulated MVS services and unique supervisor services to help support a native SNA network.
GROUP EXEC: A GCS installation tool that prompts you for the specifications needed to build a GCS configuration file.
guest: An operating system running in a virtual machine managed by a VM control program. Contrast with host.
guest operating system (GOS): A second operating system that runs on the user's primary operating system. An example of a GOS is VSE running on VM/ESA to support VM/VCNA.
guest real storage: The storage that appears real to the operating system running in a virtual machine. Contrast with guest virtual storage, host real storage, and host virtual storage.
guest virtual machine (GVM): A virtual machine in which an operating machine is running.
guest virtual storage: The storage that appears virtual to the operating system running in a virtual machine. Contrast with guest real storage, host real storage, and host virtual storage.
GVM: Guest virtual machine.

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half-duplex protocol: A communications protocol where only one communication partner can send data at a given time.
handshaking feature: See VM/VS handshaking feature.
hard requisite: (1) In VMSES/E, a prerequisite to a PTF that supplies a change required by the PTF. (2) In VMSES/E, a prerequisite to a PTF that affects the same lines of code as the PTF, so that the PTF cannot be applied without the prerequisite. (3) See also corequisite, if-requisite.
HDLC: High-level data link control.
help function: One or more display images that describe how to use application software or how to do a system operation.
heuristic damage: Damage caused to protected resources that corrupted data integrity. In a distributed system this occurs when parts of a transaction are disconnected from each other before sync point processing is complete and commit or rollback is forced to occur at one or more locations and at least one location made a decision different from the others. Heuristic damage can only occur by intervention from the outside (see heuristic decision) generally to force completion of a process that is holding locks on needed data.
heuristic decision: When distributed protected resources become disconnected during a coordinated update, and resynchronization is unable to effect a timely resolution because one or more of the resources is not active, it may be desirable to force the logical unit of work to commit or rollback. Forcing the logical unit of work to commit or rollback can cause locked resources to be made available for further processing. The decision to force the logical unit of work to commit or rollback unilaterally is called a heuristic decision. It is typically made by the system operator but it can also be a programmed decision.
high common storage: GCS common storage that resides above the 16MB line. High common storage can be used only for free storage. See common storage.
high private storage: GCS private storage that resides above the 16MB line. See private storage.
High-level data link control (HDLC): In data communication, the use of a specified series of bits to control data links in accordance with the International Standards for HDLC.
high-water mark: The highest contiguous address, starting from location zero, where the virtual system's real addresses equal the virtual system's virtual addresses.
history files: One or more CMS files that describe the changes (with a date and time stamp) made to the VM/ESA system and its installed software products.
HOLDING screen status: For a display terminal used as a virtual console under VM/ESA, an indicator located in the lower right of the screen that displays that the current contents of the screen remain on the screen until the user requests that the screen be erased. This status occurs either by pressing Enter, or it is triggered by a message or warning displayed on the screen.
host: A VM control program in its capacity as manager of a virtual machine in which another operating system is running. Contrast with guest.
host access list: A CP-maintained list which defines the address spaces that are available to an XC virtual machine when it is in access-register mode. Host access lists are not directly addressable by virtual machines; CP adds and removes entries from the host access list for the virtual machine when requested through VM/ESA services.
host access-list entry: The information in a host access list that identifies a particular address space and represents a virtual machine's capability to access it. An access-list-entry token (ALET) selects the host access-list entry to be used to access a particular storage operand.
host real storage: The storage that appears real to the control program. If VM is running native, this is real storage; if VM is running in a virtual machine, this is virtual storage. Contrast with guest real storage, guest virtual storage, and host virtual storage.
host system: A data processing system that prepares programs and the operating environments for use by another computer or controller.
host virtual storage: The storage that appears virtual to the control program. Contrast with guest real storage, guest virtual storage, and host real storage.
host-primary address space: The initial address space for a virtual machine, created by CP at virtual machine logon. This is the address space from which instructions are fetched, and from which all operands are fetched and stored when in primary-space mode. For 370, XA and ESA virtual machines, the host-primary address space represents virtual machine real storage. For XC virtual machines, the host-primary address space is one of a set of address spaces that the virtual machine may own.
hot I/O: A serious error condition caused by an I/O interruption that disrupts system operation. See hot I/O rate.
hot I/O rate: In VM/ESA, the maximum rate of consecutive unsolicited interrupts allowed by CP.

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I/O: Input/output.
I/O adapter (IOA): A hardware and microcode element which, when combined with an integrated I/O processor, enables I/O devices to be attached to a processor without requiring a physical channel.
I/O Configuration Data Set (IOCDS): The data set that contains an I/O configuration definition built by the I/O configuration program (IOCP).
I/O Configuration Program (IOCP): A program that defines to a system all available I/O devices and channel paths.
IA: Integrated adapter.
IBM System/370 to IBM Personal Computer Enhanced Connectivity Facilities
for VM/ESA: (1) A program that provides the SRPI and a communications manager on an IBM System/370 using VM/CMS. (2) The implementation of enhanced connectivity on a VM/ESA system with CMS installed.
ID card: Under VM/ESA, the identification card that indicates the destination user ID of a deck of real cards. These cards are read into the system card reader or into the card reader of an RSCS remote station.
IDRC: Improved data recording capability.
IEEE 802: A standard that describes the formats and protocols at the medium access level for an LAN. In this standard, hardware protocol requires carrier sense multiple access with collision detection. In addition, a transmitting data station that detects another signal while transmitting stops sending, sends a jam signal, and then waits for a variable time before trying again (Ethernet).
if-requisite: (1) At the system-level, a requisite of an optional product. (2) At the service-level, an out-of-component hard requisite
image library: A set of modules that define the spacing, characters, and copy modification data that a 3800 printer uses to print a spool file or that define the spacing and character set that an impact printer uses to print a spool file. See system data file.
IML: Initial microprogram load.
immediate command: A type of CMS command that, when entered after an attention interruption, causes program execution, tracing, or terminal display to stop. Another immediate command can be entered to resume tracing or terminal display. The immediate commands are HB (halt batch execution), HI (halt all REXX or EXEC 2 programs or macros), HO (halt tracing), HT (halt typing), HX (halt execution), RO (resume tracing), RT (resume typing), SO (suspend tracing), TE (trace end), and TS (trace start). They are called immediate commands because they are executed when they are entered; they are not stacked in the console stack. Within an exec, immediate commands can be established or canceled by the CMS command IMMCMD.
implicit lock: A lock automatically acquired and freed when you run CMS commands and program functions against files or directories that reside in an SFS file pool. Many readers and one writer can access a file or directory.
implied CP command: In CMS, a CP command invoked without preceding the command line with CP.
implied EXEC: An EXEC procedure invoked without identifying it as such; that is, the word exec is not used for the invocation. Only the file name is used, as if entering a CMS command.
improved data recording capability (IDRC): A feature used on 3480 and 3490 tape devices that provides an improved data recording format.
improved spool file recovery: Recovering from the disk the checkpoint data that was previously recorded for closed spool files. Thus, if warm start is not possible, the VM/ESA system operator may attempt a checkpoint start or force start. See checkpoint (CKPT) start and force start.
in-doubt: A protected resource is called in-doubt when it has successfully completed the first phase of the two-phase commit and it is waiting for a decision from the initiator to either commit or roll back the changes and therefore start the second phase of the two-phase commit.
in-memory file: An EXEC 2 term for a file resident in storage and similar in concept to a file on disk.
in-queue virtual machine: A virtual machine on the run list waiting to be dispatched.
inactive page: A page in real storage that has not been referenced during a predetermined period.
inactive work unit: A work unit on which no requests have yet been made, or an atomic request was made, or requests were made and have been committed or rolled back; that is, an inactive work unit has no uncommitted work associated with it.
indicator: A 1-byte area of storage that contains either the character "1" to denote a true condition or the character "0" to denote a false condition.
initial installation system: In VMSES/E, a functional subset of the VM/ESA system shipped on the VM/ESA system DDR tapes and used during installation of VM/ESA.
initial microprogram load (IML): The action of loading a microprogram, which is a set of elementary instructions maintained in special storage that corresponds to a specific computer operation.
initial program load (IPL): The initialization procedure that causes an operating system to begin operation. A VM user must IPL the specific operating system into the virtual machine that will control the user's work. Each virtual machine can be loaded with a different operating system. See IPL parameters, IPL processor.
initialize: To set counters, switches, addresses, or contents of storage to starting values.
initiator: The role of the CRR sync point manager when the transaction program issues a sync point request that begins the coordinated updating of distributed resources.
input area: On the VM/ESA logon screen, the area that contains input fields for a user ID, password, and command text.
input line: For typewriter terminals, information entered by a user between the time the typing element of the terminal comes to rest following a carriage return until another carriage return is typed. For display terminals, the data entered into the user input area of the screen. See user input area.
input mode: In the CMS Editor or XEDIT editor, the environment that lets the user enter new lines of data. Contrast with edit mode.
input stream: (1) The sequence of job control statements and data submitted to an operating system through an input unit especially started for this purpose by the operator. (2) In CMS Pipelines, a stream that flows into a stage. Contrast with output stream. (3) See primary input stream, secondary input stream, tertiary input stream.
input/output (I/O): (1) A device whose parts can do an input process and an output process at the same time. (2) A functional unit or channel involved in an input process, output process, or both, concurrently or not, and to the data involved in such a process.
installation verification procedure (IVP): A procedure distributed with VM/ESA that exercises the newly generated VM/ESA system. This procedure verifies that the basic facilities of VM/ESA are correctly functioning.
installation-wide exit: An interface to VM/ESA that a system programmer can use to enhance or extend the functions of a VM/ESA system. Generally, an installation-wide exit is activated for all users on the system and is run as part of a system program.
installed user program (IUP): An IBM licensed program produced by or for an individual IBM system user (customer or IBM internal). This kind of program can interface with licensed programs, or it can be a stand-alone program.
instruction address stop: An instruction address specified by a CP or CMS command, which, when fetched, causes the virtual machine to stop.
instruction counter: A counter that indicates the location of the next computer instruction to be interpreted.
instruction simulation wait: The virtual machine is in a WAIT state awaiting the completion of instruction simulation.
integrated adapter (IA): A combination of an integrated I/O processor and an I/O adapter.
integrated I/O processor (IOP): A hardware and microcode element that enables I/O devices to be attached to a processor without requiring a physical channel.
intensive recording mode: A special error recording mode that can be invoked by an IBM service representative for only one I/O device at a time. On the 1st through 10th unit checks or other error conditions specified by the service representative, an I/O error record is constructed, formatted, and written to the VM/ESA I/O error recording cylinder, after which no more errors are recorded.
Inter-System Facility for Communications (ISFC): A function of CP (in VM/ESA Rel. 1.1 and later) that handles program-to-program communications between VM systems, and between VM systems and LAN-based domain controller workstations.
inter-user communication vehicle (IUCV): A VM/ESA generalized CP interface that helps the transfer of messages either among virtual machines or between CP and a virtual machine.
interaction: A basic unit that records system activity, consisting of acceptance of a line of terminal input, processing of the line, and a response, if any.
interactive: The classification given to a virtual machine depending on this virtual machine's processing characteristics. When a virtual machine uses less than its allocation time slice because of terminal I/O, the virtual machine is classified as being interactive. Contrast with noninteractive.
interactive user: A user whose virtual machine is dispatched for the first time, or whose virtual machine had an I/O interrupt from the terminal before the previous queue had ended.
interface: A shared boundary between two or more entities. An interface might be a hardware or software component that links two devices or programs together.
intermediate communications server: A virtual machine that handles communications requests to a resource manager program for a user program.
internal trace table: See CP trace table.
interprocess communication (IPC): In CMS Multitasking, the exchange of information between processes or threads through messages placed on queues maintained by the kernel.
interrupt: A suspension of a process, such as execution of a computer program, caused by an external event and done in such a way that the process can be resumed.
invoke: To start a command, procedure, or program.
IOA: I/O adapter.
IOCDS: I/O Configuration Data Set
IOCP: I/O Configuration Program
IOP: Integrated I/O processor
IPC: Interprocess communication
IPL: Initial program load
IPL parameter: An option for an initial program load passed to CP through the stand-alone loader.
IPL processor: In an AP or MP system, the processor on which the control program was first initialized during system generation. Note that both the IPL and the non-IPL processors in a real MP configuration have I/O capabilities.
IPL volume: The volume that is IPLed and contains a loader.
ISFC: Inter-System Facility for Communications
IUCV: Inter-user communication vehicle
IUP: Installed user program.
IVP: Installation verification procedure.

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JES: Job entry subsystem.
JIB: In CMS/DOS, job information block.
job entry subsystem (JES): A system facility for spooling, job queuing, and managing I/O on MVS. Examples are JES2 and JES3.

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KB: Kilobyte.
kilobyte (KB): 1,024 bytes.

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label: (1) In programming languages, a language construction naming a statement and including an identifier. (I) (2) An identifier of a command generally used for branching. (3) In CMS Pipelines, an alphanumeric string that defines how streams are connected between stages. (4) See label definition, label reference.
label definition: In CMS Pipelines, the first occurrence of a label in a pipeline. A label definition makes it possible to connect other pipelines to the labeled stage. Contrast with label reference.
label reference: In CMS Pipelines, a second or subsequent occurrence of a label in a pipeline. A label reference defines an additional input and output stream for the stage on which the label is defined. Contrast with label definition.
LAN: Local area network.
LAN broadcast: The sending of a transmission frame intended to be accepted by all other data stations on the same LAN.
LAN multicast: The sending of a transmission frame intended to be accepted by a group of selected data stations on the same LAN.
language binding file: A C/370 header file or assembler macro to aid in using the Application Programming Interface. It defines the entry points, declares the data types of function parameters, maps long function names to external symbols, and defines constants for return codes, reason codes, and other values.
last agent optimization: An optimized flow technique that is part of the LU 6.2 sync point architecture. An initiator can pick one adjacent agent as last agent. The initiator sends this agent a request commit action rather than the (normal) prepare action (only after all other agents have responded to the prepare action, thus the term last agent). This last agent is then free to select one of its cascaded agents also to be the last, and so on. This support is architected for performance reasons.
LIFO (last-in-first-out): A queuing technique in which the next item to be retrieved is the item most recently placed in the queue. Contrast with FIFO (first-in-first-out).
limp mode: A VM/ESA system running without a CRR recovery server, which results in a serious degradation in CMS performance.
line delete symbol: Synonym for logical line delete symbol.
line deletion symbol: Synonym for logical line delete symbol.
line end symbol: Synonym for logical line end symbol.
line mode: The mode of operation of a display terminal that is equivalent to using a typewriter-like terminal. Contrast with display mode.
line number: A number located at either the beginning or the end of a record (line) that can be used during editing to refer to that line. See prompting.
line-number editing: A reference to new or existing lines in a CMS file by line number.
link: (1) In RSCS, a connection, or ability to communicate, between two adjacent nodes in a network. (2) In TSAF, the physical connection between two systems.
linking to a disk: Sharing a disk owned by another user. A user can share the disk on a temporary or permanent basis. The sharing is usually read-only and can require a password to access the data.
listening mode: A type of CRR participation in which the participating resource or product registers only for the postcoordination function, because the resource or product only needs to know when sync points occur and what their outcome is.
load: In installation and service, to move files from tape to disk, auxiliary storage to main storage, or minidisks to virtual storage within a virtual machine.
load map: A map containing the storage addresses of control sections and entry points of a program loaded into storage.
loadable unit: In VMSES/E, a portion of a product that can be installed independently of the rest of the product, but is serviced as part of the product.
loader: A routine, commonly a computer program, that reads data into main storage.
local: (1) Pertaining to either of two entities (for example, a user and a server) that belong to the same system within a collection or to the same node within an SNA system. (2) Pertaining to a device accessed directly without use of a telecommunication line. (3) Contrast with remote. (4) See local area network (LAN), local ID, local disk, local modification, local program, local resource, local resource manager, local service, local string, local tracking number, locally known LU name.
local area network (LAN): A data network located on the user's premises in which serial transmission is used for direct data communication among data stations. Contrast with wide area network (WAN).
local disk: In VMSES/E, a minidisk or SFS directory containing local service, customized files, and any circumventive service.
local ID: In SFS, the user ID on your local system of some remote user.
local modification: Synonym for local service.
local program: The conversation partner being discussed within a particular context. Contrast with remote program.
local resource: (1) A resource accessible from only within a single VM/ESA system and whose identity is known only within a single VM/ESA system in the CS or TSAF collection. (2) A resource accessible from only within a single OS/2 Extended Edition or AIX PS/2 workstation running VM PWSCS. Contrast with global resource, private resource, and system resource.
local resource manager: (1) An application that runs in a virtual machine and identifies itself to the local system in the CS or TSAF collection as a local resource owner using *IDENT. (2) An application that runs in an OS/2 Extended Edition or AIX PS/2 workstation running VM PWSCS. Contrast with global resource manager, private resource manager, and system resource manager.
local service: (1) Change applied to a product without using VMSES/E. (2) See also circumventive service and user modification. (3) Synonymous with local modification.
local string: In VMSES/E, the set of local disks.
local tracking number: The unique identifier assigned to a local modification. The local tracking number is used in the file type of update files and in the update file identification records of auxiliary control files. Each installation has its own system of local tracking numbers.
locally known LU name: (1) An LU name that transaction programs use to identify a communications partner in a TSAF or CS collection. (2) The LU name used by transaction programs to identify a remote LU in the SNA network.
lock: (1) A restriction on concurrent use of an SFS file, directory, file space, or storage group. (2) To restrict concurrent use of an SFS object.
locked page: A page that is not to be paged out.
log data: Information that a communications program can send to its partner to help diagnose errors.
log minidisks: (1) In SFS, two duplicate minidisks that contain information about changes made to the file pool. SFS file pool servers use the SFS log minidisks to help protect the integrity of the file pool if a system failure occurs. (2) In CRR, two duplicate minidisks that contain information about the states of various logical units of work during sync point processing. CRR recovery servers use the CRR log minidisks to perform resynchronization processing to protect the integrity of the transaction if a failure occurs during sync point processing.
logical character delete symbol: A special editing symbol, usually the at (@) sign, that causes CP to delete it and the immediately preceding character from the input line. If many delete symbols are consecutively entered, that same number of preceding characters are deleted from the input line. The value can be redefined or unassigned by the installation or the user. Synonymous with character delete symbol.
logical editing symbols: Symbols that let the user correct entering errors, combine multiple lines of input on one physical line, and enter logical editing symbols as data. The logical editing symbols can be defined, reassigned, or unassigned by the user. See logical character delete symbol, logical escape symbol, logical line delete symbol, and logical line end symbol.
logical escape symbol: A special editing symbol, usually the double quotation (") symbol, that causes CP to consider the immediately following character as a data character instead of as a logical editing symbol. Synonymous with escape symbol.
logical line: A command or data line that can be separated from one or more additional command or data lines on the same input line by a logical line end symbol.
logical line delete symbol: A special editing symbol, usually the cent (›) sign, that causes CP to delete the previous logical line in the input line back to and including the previous logical line end symbol. Synonymous with line delete symbol and line deletion symbol. See logical line.
logical line end symbol: A special editing symbol, usually the pound (#) sign, that lets the user enter the equivalent of several command or data lines in the same physical line; that is, each logical line except the last line is terminated with the logical line end symbol. Synonymous with line end symbol.
logical operator: The name given to the virtual machine from which OPERATOR functions requested by the Programmable Operator Facility virtual machine are done. This name can also describe the person who usually operates the Logical Operator virtual machine. In a mixed environment, an NCCF operator can be assigned as the logical operator to control a VM distributed system.
logical record: A formatted record that consists of a 2-byte logical record length and a data field of variable length.
logical record interface (LRI): Builds logical records from record segments on input and breaks logical records into segments on output for the application. LRI is used with QSAM spanned records.
logical saved segment: A saved segment defined by CMS within a physical saved segment. A single physical saved segment can contain many logical saved segments. A logical saved segment can contain different types of program objects, such as MODULE files, TEXT files, execs, callable services libraries, language information files, user-defined objects, or a single minidisk directory. See also physical saved segment.
logical segment definition file: A file that identifies the contents of a logical saved segment.
logical unit (LU): An entity addressable within an SNA-defined network, similar to a node within a VM network. LUs are categorized by the types of communication they support. A TSAF collection in an SNA network is viewed as one or more LUs.
logical unit name (LU name): A symbolic name given to a particular LU in an SNA-defined network.
logical unit of work: (1) In SFS, a group of related operations that the SFS file pool server is doing for a user. The operations in a logical unit of work can either be committed or rolled back as a unit. Sometimes this is called a resource logical unit of work. (2) In CRR, a logical unit of work is a convenient abstraction for the application processing (including the underlying system support) performed to take a set of protected resources (such as SFS file pools) from one consistent state to another (commit changes) in such a way that the unit of work appears atomic. If a failure occurs during the sync point processing of a logical unit of work, any changes made by (or for) the logical unit of work are rolled back, so that the protected resources are returned to their previous consistent state. A CRR logical unit of work is frequently called a transaction or LUWID and consists of one or more LUWID instances.
logical unit of work identifier (LUWID): The identifier of a CRR logical unit of work. The LUWID includes three parts: the fully qualified LU network name; the instance number, which is unique at the LU that creates it; and the sequence number, which is incremented by one following a sync point. Also, the conversation correlator is used to further qualify LUWIDs.
logically connected terminal: A terminal connected by leased or switched telecommunications or by local attachment to a multiple-access virtual machine by the CP DIAL command.
logically sparse file: A file that contains sparse records.
logo configuration file: A file that selects logo picture files for terminals and printers and text files for certain areas of the logon screen.
logo picture file: A file that contains the logon screen logo for a particular system.
logoff: The procedure by which a user ends a terminal session.
logon: The procedure by which a user begins a terminal session.
look-aside entry: A nucleus resident routine becomes a look-aside entry after it has been executed.
low common storage: GCS common storage that resides below the 16MB line. See common storage.
low private storage: GCS private storage that resides below the 16MB line. See common storage.
LRI: Logical Record Interface.
LU: Logical unit.
LU name: Logical unit name.
LU type 6: A set of protocols and services defined by IBM's SNA for communication between application programs.
LUWID: Logical unit of work identifier.
LUWID instance: A subset of a CRR logical unit of work (transaction) that is identified by the LUWID and represents the work done by a user ID for this LUWID. An LUWID instance consists of one or more resource logical units of work.

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MAC: mandatory access control.
machine: A synonym for a virtual machine running under the control of VM/ESA.
machine ID: A 2-byte field that uniquely defines a virtual machine within a virtual machine group. Machine ID is sometimes combined with task ID to uniquely identify a task within the virtual machine group.
MACLIB library: A library that contains macros, copy files, or source program statements for use under CMS.
macro: Abbreviation for macrodefinition and macroinstruction.
macro library: A library of macrodefinitions.
macrodefinition: A set of statements that defines the name of, format of, and conditions for generating a sequence of assembler language statements from a single source statement. Synonymous with macro.
macroinstruction: In assembler language programming, an assembler language statement that causes the assembler to process a predefined set of statements called a macrodefinition. The statements usually produced from the macrodefinition replace the macroinstruction in the program. Synonymous with macro.
mandatory access control (MAC): A security regimen that governs which subjects can access which objects, and in what way, based upon the relationship between their security labels. Mandatory access control restricts a subject's access to an object based upon three things:
map: (1) In CMS, the file that contains a CMS output listing, such as (i) a list of macros in the MACLIB library, including macro size and location within the library; (ii) a listing of the directory entries for the DOS/VS system or private source, relocatable, or core image libraries; (iii) a linkage editor map for CMS/DOS programs; and (iv) a module map containing entry point locations. (2) A set of values having defined correspondence with the quantities or values of another set. (I) (A) (3) To show relationships between objects.
mapped conversation: A conversation where data is sent in arbitrary length buffers. Programs do not have to be concerned with the format of data being sent. Contrast with basic conversation.
master file directory: A directory on each CMS disk that contains the name, format, size, and location of all the CMS files on the disk. When a disk is accessed by the ACCESS command, the directory is read into main storage and identified with one of the 26 disk mode letters (A through Z).
master file directory block: Synonym for CMS minidisk file directory.
MB: Megabyte.
MCCU: Multisystem channel communications unit.
MDISK: (1) Another name for minidisk. (2) The VM directory statement that describes a user's storage space.
megabyte (MB): 1,048,576 bytes.
member saved segment: A saved segment that begins and ends on a page boundary and belongs to up to 64 segment spaces. A member saved segment is accessed by its own name or by the name of a segment space to which it belongs. A member saved segment may contain logical saved segments. Contrast with discontiguous saved segment.
memo-to-users: (1) A file provided on a service tape that contains specific service information for a product. (2) user memo.
merge: When receiving files from a service tape using VMFMRDSK, the process of moving existing service files from each minidisk or SFS directory in the target string to the minidisk or directory that contains the previous service level. The result is that the primary target minidisk or directory is left empty and ready to receive the latest service.
message: Data sent from a source application to a target application program in a conversation. See message text, message key,message header, message queue, message repository.
message header: The leading part of a message that contains information such as the source or destination code of the message, the message priority, and the type of message.
message key: In CMS Multitasking, a part of the message text that describes or qualifies the message in some way.
message level: In CMS Pipelines, a number specifying which informational messages you can receive from CMS Pipelines. These messages include: DMS2651I, DMS2652I, DMS2653I, and DMS2654I. Depending on the message level, you can receive these messages along with other messages. These messages help to determine what stage was running, what pipeline subcommand was running, and what pipeline was running that caused the previous message to be issued.
message queue: A list of messages awaiting processing or waiting to be sent to a terminal.
message repository: A source file that contains message texts for a VM component or user application. It is compiled into internal form by the GENMSG command. The message text in a repository file can be translated and used to support national languages.
message text: The part of a message of concern to the party ultimately receiving the message, that is, the message exclusive of the header or control information.
MIH: Missing interrupt handler.
minidisk: (1) A logical subdivision (or all) of a physical disk pack that has its own virtual device address, consecutive virtual cylinders (starting with virtual cylinder 0), and a VTOC or disk label identifier. Each user virtual disk is preallocated and defined by a VM/ESA directory entry as belonging to a user. (2) See CMS minidisk file directory, CMS system minidisk, control minidisk, full-pack minidisk,log minidisks, minidisk directory, minidisk pool, minidisk-relative block number.
minidisk directory: Synonym for CMS minidisk file directory.
minidisk pool: A logical DASD containing one or more DASD or minidisk extents that are formatted with 4K records. It is mapped to address spaces.
minidisk-relative block number: A 4K record contained on a minidisk or DASD extent with its origin relative to zero.
minimum truncation: The shortest form of a command name, operand, or option that can be entered and still be recognized by VM/ESA. For example, AC is the minimum truncation for the ACCESS command. However, note that the letter A is the minimum truncation for ASSEMBLE. See truncation.
missing interrupt handler (MIH): A VM/ESA facility that detects incomplete I/O conditions by monitoring I/O activity. It also tries to correct incomplete I/O conditions without operator intervention.
mode name: Part of the CPI Communications side information. The mode name is used by LU 6.2 to designate the properties for the session that will be allocated for a conversation.
module: (1) A program unit that is discrete and identifiable with respect to compiling, combining with other units, and loading; for example, the input to or output from an assembler, compiler, linkage editor, or executive routine. (A) (2) A nonrelocatable file whose external references have been resolved.
MORE screen status: For a display terminal used as a virtual console under VM/ESA, an indicator located in the lower right of the screen that displays when the user's display screen is full and more data will be displayed. After 60 seconds, the screen is automatically erased and the next screen is displayed. To immediately clear the screen, press the Clear, Cancel, or PA2 key. To hold the data on the screen longer than 60 seconds, press the Enter key to enter HOLDING status. See HOLDING screen status.
MP: Multiprocessor.
multiple preferred guests: A facility that supports up to six preferred virtual machines when the Processor Resource/Systems Manager (PR/SM) feature is installed in the real machine. See preferred virtual machine.
multiple user mode: In a file pool server machine, a mode of file pool server processing during which it processes user requests for file pool data. (The CMS FILESERV START command starts multiple user mode processing.) Contrast with dedicated maintenance mode.
Multiple Virtual Storage (MVS): An alternative name for OS/VS2.
multiple-access virtual machine: A virtual machine running under VM/ESA that supports teleprocessing terminals.
multiprocessor (MP): A computer using two or more processing units under integrated control.
multistream pipeline: In CMS Pipelines, a pipeline that contains at least one stage that has more than one input stream, more than one output stream, or both.
multisystem channel communications unit (MCCU): An I/O device; for example, the 3088 MCCU, which interconnects up to eight systems using block-multiplexer channels.
multitasking: Providing services for many tasks that are active at the same time.
multivolume file: A file that occupies more than one tape reel.
mutex: In CMS Multitasking, a variable with an associated wait queue used to enforce mutual exclusion from a shared resource. CMS Multitasking allows only one thread at a time to acquire the mutex, and only the thread that has acquired the mutex can execute the critical section of code for the resource. See also semaphore.
MVS: Multiple Virtual Storage.
MVS page fault assist: A standard hardware feature on the IBM 3081 processor complex that reduces the time needed by the MVS/SP virtual machine to handle page translation exception interruptions. The MVS/SP V=R guest gets these interruptions the first time certain tasks access storage using the GETMAIN macroinstruction. The virtual machine assist extension for the IBM 3033 extension feature (6850) must be in place so that the user can get MVS/SP page fault assist on the IBM 3033 processor.
MVS/Bulk Data Transfer (BDT): An IBM licensed program that (1) copies sequential or partitioned data sets from a JES3 or JES3 computer complex to another JES2 or JES3 computer complex within an SNA network, and (2) lets JES3 computer complexes participate in an SNA NJE network.

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named saved system: Synonym for saved system.
named system: A system that has an entry in the CP system name table (DMKSNTBL). The entry in the system name table includes the system name and other pertinent data so that the system can later be saved. See saved system.
namedef: A temporary name that represents either: (1) a file name and file type, or (2) an SFS directory name. Namedefs are used in program functions so that it is not necessary to directly code a file name and file type or directory name in the program.
native mode: Refers to running an operating system stand-alone on the real machine instead of under VM/ESA.
native SNA: SNA operating without a separate GOS (VS1 or VSE).
native SNA network: A VM/ESA network that operates according to the conventions of SNA and functions as part of a VM/ESA system without help from a GOS.
NCCF: Network Communication Control Facility.
NCP: Network control program.
NCPDUMP: Network control program DUMP.
negative prerequisite: In VMSES/E, a product that cannot exist on a system at the same time as another product.
netdata: The name of the format that sends a file when the NEW option of the CMS SENDFILE command is specified.
network: Any set of two or more computers, workstations, or printers linked in such a way as to let data be transmitted between them.
Network Communication Control Facility (NCCF): An IBM licensed program consisting of a base for command processors that can monitor, control, and improve the operation of a network.
network control program (NCP): An IBM licensed program that provides communication controller support for single-domain, multiple-domain, and interconnected network capability.
network job entry (NJE): A facility for transmitting jobs, sysout data sets, operator commands and operator messages, and job accounting information from one computing system to another. NJE is supported by JES2, JES3, RSCS, VSE/POWER, and BDT.
NJE: Network job entry.
node: (1) A single processor or a group of processors in a teleprocessing network. (2) A computer, workstation, or printer, when it is participating in a network.
node ID: Node identifier.
node identifier (node ID): The name by which a node is known to all other nodes in a network.
non-IPL processor: In an AP or MP system, the attached or second processor initialized at system generation time. Note that both the IPL processor and the non-IPL processor in a real MP configuration have I/O capabilities.
nondisruptive transition: A facility that lets an installation transfer control of an operating system from VM/ESA virtual machine mode to native mode (and vice versa) without having to shut down and reinitialize the operating system.
noninteractive: The classification given to a virtual machine depending on the virtual machine's processing characteristics. When a virtual machine usually uses all its allocated queue slice, it is classified as being noninteractive or compute bound. Contrast with interactive.
noninteractive user: A user whose virtual machine completed its previous queue slice without having an I/O interrupt from the terminal.
nonpaging mode: Synonym for OS/VS1 nonpaging mode.
nonprivileged program: In GCS, a program called by a GCS application that operates in problem state. Contrast with privileged program.
nonresident pages: Pages whose contents are on DASD but not in real storage. A page is considered nonresident when an attempt to load its real address returns a nonzero condition code.
nonsynchronous processing for DASD: A buffer is inserted in the control unit data path, between the device and the channel. With this configuration, channel data is typically not transferred for each system channel operation when the target data field passes the read/write head on the device.
nonvolatile storage (NVS): Additional random access electronic storage available with a 3990 Model 3 Storage Control, used to retain data during a power failure. Nonvolatile storage, accessible from all storage directors, stores data during DASD fast-write operations.
NOT ACCEPTED screen status: For a display terminal used as a virtual console under VM/ESA, an indicator in the lower right of the screen that displays that the user is: (1) trying to enter another command line, but the terminal buffer still contains a previous command line, and (2) using the copy function to copy the contents of the screen onto an associated hardcopy printer; however, the printer is busy, nonexistent, or otherwise unavailable.
NPT: Nonprogrammable terminal.
NSS: Named saved system.
nucleus: The part of CP and CMS resident in main storage.
NUCON: The nucleus constant area of CMS.
null line: A logical line with a length of zero that usually signals the CMS Editor to end input mode and enter edit mode. In VM/ESA, a null line for typewriter terminals is a terminal input line consisting of a return character as the first and only information, or a logical line end symbol as the last character in the data line. For display devices, a null line is indicated by the cursor positioned at the beginning of the user input area or the data in the user input area ending with a logical line end symbol.
null string: (1) A string containing no element. (T) (2) A character string with a length of zero. (3) In CMS Pipelines, a delimited string formed by two adjacent delimiters.
NVS: Nonvolatile storage.

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+---+ O +---+

object: (1) In computer security, a passive entity that contains or receives information. Access to an object implies access to the information it contains. Example of objects in VM/ESA are: minidisks, spool files, named saved segments, and virtual storage. Contrast with subject. (2) In VMSES/E, a usable form defined in build lists. (3) In VMSES/E, a built part of a product. A product consists of many objects, such as, nuclei, modules, execs, help files, and macrolibraries. (4) See external object, object code, object module, public object.
object code: Compiler or assembler output that is executable machine code or is suitable for more processing to produce executable machine code. Contrast with source code.
object module: A module that is the output of an assembler or a compiler and is input to a linkage editor.
offline: (1) Pertaining to the operation of a functional unit that takes place either independently of, or in parallel with, the main operation of a computer. (T) (2) Neither controlled by, nor communicating with, a computer. Contrast with online.
OLTS: Online test system.
OLTSEP: Online test stand-alone executive program.
one-phase commit protocol: This is outside the CRR sync point architecture. Resources that are committed by this method are not recorded in the CRR log. The one-phase commit protocol may be used when a single resource has been changed and a commit request issued for it.
online: (1) Pertaining to the operation of a functional unit when under the direct control of the computer. (T) (2) Pertaining to a user's ability to interact with a computer. (A) (3) Pertaining to a user's access to a computer via a terminal. (A) (4) Controlled by, or communicating with, a computer. (5) Contrast with offline. (6) See online message, online test stand-alone executive program (OLTSEP), online test system (OLTS), simultaneous peripheral operations online (SPOOL).
online message: The text that appears in the top area of a logon screen.
online test stand-alone executive program (OLTSEP): A program IBM uses for I/O maintenance.
online test system (OLTS): A system that lets a user test I/O devices concurrently with execution of programs. Tests can be run to diagnose I/O errors, verify repairs and engineering changes, or to periodically check devices.
operand: Information entered with a command name to define the data on which a command processor operates and to control the execution of the command processor.
Operating System/Virtual Storage (OS/VS): A family of operating systems that control System/370 computing systems. OS/VS includes VS1, VS2, MVS/370, MVS/XA, and MVS/ESA.
operators console: A functional unit containing devices that communicate between a computer operator and an automatic data processing system.
optimized last agent: See last agent optimization.
option: (1) A specification in a statement that may be used to influence the execution of the statement. (2) In CMS Pipelines, a keyword that controls the execution of a stage, the PIPE command, the ADDPIPE pipeline subcommand, or the CALLPIPE pipeline subcommand.
ordered seek queuing: A technique the CP I/O supervisor uses to minimize seek time. This is done by scheduling DASD I/O operations for nondedicated disks in a sequential progression of cylinder numbers.
ordinary application: A GCS application, started with the OSRUN command, that operates in problem state. Contrast with authorized application.
OS simulation under CMS: The environment of CMS that permits the simulation of OS functions. Contrast with CMS/DOS.
OS/MFT: The IBM System/360 Operating System that supports multiprogramming with a fixed number of tasks.
OS/MVT: The IBM System/360 Operating System that supports multiprogramming with a variable number of tasks.
OS/VS: Operating System/Virtual Storage.
OS/VS1: A virtual storage operating system that is an extension of OS/MFT. Synonymous with nonpaging mode.
OS/VS1 nonpaging mode: If OS/VS1 executes under the control of a VM/ESA system that supports the VM/VS handshaking feature and if the OS/VS1 address space is equal to the size of its VM/ESA virtual machine, OS/VS1 executes in nonpaging mode. When OS/VS1 executes in nonpaging mode, it uses fewer privileged instructions and avoids duplicate paging because paging is done only by CP.
OS/VS2: A virtual storage operating system that is an extension of OS/MVT.
OS/2 domain controller: An OS/2 Extended Edition application that is a program-to-program communications gateway, enabling user programs to connect to and communicate with resources on VM systems or other programmable workstations in a CS collection. See also AIX domain controller, AIX PS/2 domain controller, VM/ESA domain controller.
out-of-component requisite: In VMSES/E, a PTF to product B that is required by a PTF to product A. See also if-requisite.
output display area: For display devices, the upper portion of the display screen that contains an historical log of the most recent lines of console input to and output from the virtual machine and CP. On the 3270, this area is protected; that is, the user is unable to enter information into the output display area. The CMS Editor does not use this display format.
output stream: (1) In CMS Pipelines, a stream that flows out of a stage. Contrast with input stream. (2) See primary output stream, secondary output stream, tertiary output stream.
overhead: The additional processor time charged to each virtual machine for the CP functions needed to simulate the virtual machine environment and for paging and scheduling time.
overlay: The technique of repeatedly using the same areas of internal storage during different stages of a program.
override: (1) Synonym for component parameter override. (2) See override area, override file, class override file, component override, component override area, product parameter override file.
override $PPF: Synonym for product parameter override file.
override area: Synonym for component override area.
override file: Synonym for class override file and product parameter override file.

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pack: A set of flat, circular recording surfaces that a disk storage device uses. Sometimes called a "disk pack."
page: (1) A fixed-length block that has a virtual address and can be transferred between real storage and auxiliary storage. (2) See external page storage, external page storage management, inactive page, locked page, MVS page fault assist, nonresident pages, page-aligned, page frame, page frame table, page locking, page number, page reclamation, page table, page zero, pageable nucleus, pageable virtual machine, pseudo page fault, reserved page frame performance option, shadow page table.
page frame: A block of 4096 bytes of real storage that holds a page of virtual storage.
page frame table: A table (called the CORTABLE) that contains an entry for each frame. Each frame table entry describes how the frame is being used.
page locking: Marking a page as nonpageable so that it remains in real storage until released.
page number: The part of a virtual storage address needed to refer to a page.
page reclamation: Making available and addressable the contents of a page in real storage that is waiting to be (or already has been) paged out. Page reclamation can occur after a page fault or after a request to fix or load a page, as long as no page-in operation has been scheduled for that particular page frame.
page table: A table (labeled PAGTABLE) that indicates whether a page is in real storage and that correlates virtual addresses with real storage addresses.
page zero: Storage locations 0 to 4095.
page-aligned: In fixed-block architecture, having a starting block number that is a multiple of eight and containing a number of blocks that is a multiple of eight.
pageable nucleus: Less frequently used portions of the CP nucleus not usually resident in real main storage.
pageable virtual machine: Synonymous with virtual=virtual machine.
paging: Transferring pages between real storage and external page storage.
paging activity indexes: Values that affect the algorithm that CP uses in controlling the dispatching and scheduling of all active logged-on virtual machines.
paging area: An area of direct access storage (and an associated area of real storage) that CP uses for the temporary storage of pages when paging occurs.
paging supervisor: A part of the CP nucleus that allocates and releases real storage page frames for pages, selects the appropriate paging device, and initiates page-in and page-out operations. This is based on ordered seek queuing and slot sorting techniques. See ordered seek queuing and slot sorting.
parallel processing: (1) The concurrent or simultaneous execution of two or more processes in a single unit. (A) (2) In CMS Multitasking, the execution of threads of a particular application at the same time on different real CPUs of the real processor complex.
parameter: A variable that is given a constant value for a specified application and that may denote the application. component parameter override, extended PLIST (untokenized parameter list), parameter driven installation, parameter list (PLIST), product parameter file (PPF), product parameter override file, tokenized PLIST (parameter list), untokenized parameter list.
parameter driven installation: An installation method in which instructions for the installation are given at the beginning of the process rather than in response to prompts during the process.
parameter list (PLIST): In CMS, a string of 8-byte arguments that call a CMS command or function. The first argument must be the name of the command or function to be called. General register 1 points to the beginning of the parameter list.
parent directory: (1) The directory for a CMS disk that has a disk extension defined for it by the ACCESS command. (2) In SFS, the next higher-level directory in which the current directory is defined.
parm disk: A disk that CP accesses during IPL. The parm disk contains all the system definition information required at IPL, for example, the system configuration and logo configuration files. See parm disk volume.
parm disk volume: The volume on which the parm disk resides. This volume can be the same one as the IPL volume and the system residence volume.
part: (1) A CMS file provided on a product tape or service tape as input to the build process. A part is the smallest serviceable unit of a component. (2) See part handler, parts catalog, PTF parts list, VM part catalog table.
part handler: An exec provided by VMSES/E that builds a specific type of object or loads parts from service media.
partner: Synonym for conversation partner.
parts catalog: In VMSES/E, a set of software inventory files that catalog all parts of a product on a minidisk or SFS directory. All product parts are cataloged when they are loaded onto the system, when they are generated, and when they are moved.
password: In computer security, a string of characters known to the computer system and a user, who must specify it to gain full or limited access to a system and to the data stored within it.
patch: A circumventive service change applied directly to object code in a text deck in a nucleus.
patch update file: A file containing a single patch. The file can also specify requisites for applying the patch.
path: In APPC/VM or IUCV, a connection between two application programs that are on the same or different systems. Paths have names assigned to them.
PC: Personal computer.
PDI: Parameter driven installation.
peer system: From the perspective of a particular system node in a network, an equivalent system; one with which jobs and data can be mutually exchanged.
performance option: One or more functions that can be assigned to a virtual machine to improve its performance, response time (if terminal-oriented), or throughput under VM/ESA.
personal computer (PC): A desk-top, floor-standing, or portable microcomputer that usually consists of a system unit, a display monitor, a keyboard, one or more diskette drives, internal fixed-disk storage, and an optional printer.
PF key: Programmed function key.
PGR: Presentation graphics routines.
physical saved segment: A member saved segment or discontiguous saved segment in which logical saved segments may be defined. See also logical saved segment, saved segment.
physical screen: Synonym for screen.
physical segment definition file: A file that identifies the logical saved segments to be included within a physical saved segment.
physical unit block (PUB): In a VSE system, an entry in a table containing the channel and device address of a device. There is a physical unit block for each physical device available in the system.
PIE: Program interrupt element.
PIN: Problem identification number.
pinned data: Data that is held in a 3990 Model 3 Storage Control because of a permanent error condition. The data can be destaged to DASD or explicitly discarded. Pinned data exists only when using fast-write.
pipeline: (1) In CMS Pipelines, a series of programs, called stages, each performing part of a task and passing the results to the next stage. Several parts of different tasks can be performed concurrently. (2) See multistream pipeline, pipeline subcommand, subroutine pipeline.
pipeline subcommand: In CMS Pipelines, a subcommand that can be issued from a user-written stage command or with the PIPCMD stage command. Pipeline subcommands process data and interact with the calling pipeline.
PLIST: Parameter list.
PMA: Preferred machine assist.
pool-relative block number: A 4K record contained within a minidisk-pool with its origin relative to zero.
POOLDEF file: A CMS file with a file type of POOLDEF that contains information that an SFS file pool server and CRR recovery server use to locate all the minidisks in their file pools.
PPF: Product parameter file.
PR/SM: Processor Resource/Systems Manager.
predefined function: A specialized function, invoked by a keyword, that has been built into the system program code because it is commonly required by many users; applies to CMS EXEC, EXEC2, and REXX.
preferred auxiliary file: In CMS, an auxiliary file that applies to a particular version of a source module to be updated, if multiple versions of the module exist.
preferred paging area: A special area of auxiliary storage where frequently used pages are paged out. It provides high-speed paging.
preferred virtual machine: A particular virtual machine that has one or more of the performance options assigned to it.
prefix area: The five left-most positions on the XEDIT full-screen display, in which prefix subcommands or prefix macros can be entered. See prefix macros and prefix subcommands.
prefix macros: XEDIT macros entered in the prefix area of any line on a full-screen display. See prefix area.
prefix storage area (PSA): A page zero of real storage that contains machine-used data areas and CP global data.
prefix subcommands: XEDIT subcommands entered in the prefix area of any line on a full-screen display. See prefix area.
prepared: In SFS, a synonym for in-doubt.
prerequisite: (1) A change that must be applied to the system before another change can be applied. (2) In VMSES/E, at the system level, a product that must be installed before another product can be installed. (3) In VMSES/E, at the service level, a PTF that must be applied before another PTF can be applied.
presentation graphics routines (PGR): In System/38 and System/370, routines within the API that let charts be defined and displayed procedurally through function routines. Contrast with graphical data display manager (GDDM).
preventive service: The application of all PTFs from a PUT or RSU. Contrast with selective preventive service.
primary address space: See host-primary address space.
primary input stream: In CMS Pipelines, the input stream defined by specifying a stage. It is input stream number 0.
primary output stream: In CMS Pipelines, the output stream defined by specifying a stage. It is output stream number 0.
primary paging device: The DASD with the highest effective data rate available for CP use. CP always attempts to store pages on this paging device instead of on slower paging devices if space on the primary paging device is available.
primary system operator: The first CP privilege class A user logged on to VM/ESA after system initialization.
primary system operator privilege class: The CP privilege class A user. This operator has primary control over the VM/ESA system and can enable and disable teleprocessing lines, lock and unlock pages, force users off the VM/ESA system, issue warning messages, query, and set (and reset) performance options for selected virtual machines, and invoke VM/ESA accounting. If the current primary system operator logs off, the next class A user to log on becomes the primary system operator.
primary-space mode: An address translation mode in which storage operands are always considered to reside in the primary address space. Access registers are not used to resolve addresses when in primary-space mode. The SET ADDRESS SPACE CONTROL instruction can be used to change the PSW to enter and exit primary-space mode. See also access-register mode.
print inhibit: A hardware feature available on some typewriter terminals, such as the 2741, that lets the user enter information with a keyboard without causing the data to be typed on the terminal's typewriter.
Print Services Facility/VM (PSF/VM): The access method that supports the 3800 Printing Subsystem Models 3 and 8. PSF can interface either directly to a user's application program or indirectly through the JES of MVS.
printer universal character set: A printer feature that permits a variety of character arrays. Synonymous with universal character set.
priority performance option: A virtual machine parameter that influences the internal scheduling algorithm of the VM/ESA control program. The lower the priority value specified, the higher the priority of the virtual machine.
private gateway: (1) A gateway that programs outside a CS or TSAF collection can use to access private resources inside the collection. (2) A gateway that nonglobal resource manager programs can use to access resources outside a CS or TSAF collection. Contrast with global gateway and system gateway.
private resource: A resource accessible from anywhere within a CS or TSAF collection or SNA network and whose identity is known only within a single workstation or virtual machine. Contrast with global resource, local resource, and system resource.
private resource manager: An application that runs in a server workstation or virtual machine and provides a service for connecting programs, but that does not identify itself to the CS or TSAF collection. Contrast with global resource manager, local resource manager, and system resource manager.
private storage: A combination of application code and GCS code available to only one particular virtual machine. No virtual machine can access or share another's private storage area.
privilege class: One or more classes assigned to a virtual machine user in a VM/ESA directory entry; each privilege class specified lets a user access a logical subset of the CP commands. There are nine IBM-defined privilege classes that correspond to specific administrative functions. They are:
privileged instruction simulation: The CP-incurred overhead to handle privileged instructions for virtual machine operating systems that execute as if they were in supervisor state but that are executing in problem state under VM/ESA. See virtual machine assist (VMA).
privileged program: In GCS, a program called by a GCS application that operates in supervisor state and uses privileged functions. A privileged program is one that meets either of the following requirements:
problem state: A state during which the central processing unit cannot execute I/O and other privileged instructions. VM/ESA runs all virtual machines in problem state. See privileged instruction simulation. Contrast with supervisor state.
process: (1) A systematic sequence of operations to produce a specified result. A process is usually logical, not physical. (2) In CMS Multitasking, a collection of threads performing related work. A process can have resources associated with it, such as storage subpools, queues, open files, and APPC conversations. All threads in a process have equal access to the resources associated with the process.
Processor Resource/Systems Manager (PR/SM): A feature available with certain processors that provides for logical partitioning of the real machine and support of multiple preferred guests. See multiple preferred guests.
product: (1) Any separately installable software program, whether supplied by IBM or otherwise, distinct from others and recognizable by a unique identification code. The product identification code is unique to a given product, but does not identify the release level of that product. (2) See product parameter file (PPF), product parameter override file, software product, product service upgrade (PSU), product tape.
product parameter file (PPF): A file containing installation and service parameters for a product: control options, minidisk and SFS directory assignments, and component part type/function lists.
product parameter override file: A file containing one or more component override areas.
product service upgrade (PSU): A procedure used to upgrade the service level of a product or component using a recommended service upgrade (RSU) tape.
product tape: A tape containing components or products to load and build.
PROFILE EXEC: A special EXEC procedure with a file name of PROFILE that a user can create. The procedure is usually executed immediately after CMS is loaded into a virtual machine (also known as IPL CMS).
program stack: Temporary storage for lines (or files) being exchanged by programs that execute under CMS. See console stack.
program state: A state associated with each partner in a conversation. This state defines the functions that a communication program can issue at a given time.
program status word (PSW): An area in storage used to indicate the order in which instructions are executed, and to hold and indicate the status of the computer system.
program temporary fix (PTF): Code changes needed to correct a problem reported in an APAR. The corrected code is included in later releases. A PTF contains one or more APAR fixes. For object-maintained parts that are changed, the PTF includes replacement parts. For source-maintained parts that are changed, the PTF includes update files and replacement parts. Each PTF is unique to a given release of a product. If the same problem occurs in multiple releases of a product, a separate PTF is defined for each release.
program update service: Receiving the contents of a PUT, applying all or some of the changes, and rebuilding the serviced parts. See preventive service and selective preventive service.
program update tape (PUT): A tape containing a customized collection of service tapes (preventive service) to match the products listed in a customer's ISD (IBM Software Distribution) profile. Each PUT contains cumulative service for the customer's products back to earlier release levels of the product still supported. The tape is distributed to authorized customers of the products at scheduled intervals or on request.
programmable operator facility: This CMS facility enables automatic filtering and routing of messages from a specified virtual machine (for example, the operator) to a logical operator virtual machine in a local distributed or mixed environment. It also permits installation defined actions to be automatically performed.
programmable station: An I/O configuration that must be programmed before it can communicate with other remote stations that adhere to a compatible protocol.
programmed function (PF) key: On a terminal, a key that can do various functions selected by the user or determined by an application program.
programmed symbols: A feature that allows definition of user-indicated shapes or symbols.
projected working set: An estimate of the number of pages of real storage that must be allocated to an in-queue virtual machine if it is to avoid excessive paging. It determines whether the virtual machine can be added to the run list from an eligible list.
prompt: A displayed message that describes required input or gives operational information.
prompting: An interactive technique that lets the program guide the user in supplying information to a program. The program types or displays a request, question, message, or number, and the user enters the desired response. The process is repeated until all the necessary information is supplied.
protected conversation: An APPC conversation that is allocated (initiated) with the SYNC_LEVEL=SYNCPT option between two application programs. When one of the application programs issues a commit (or roll back), the CRR sync point manager notifies (by means of the protected conversation) the other application program to issue a commit (or roll back). CRR processing handles the actual committing (or rolling back) of both of the application programs' work. Applications that use protected conversations must follow the rules of the LU 6.2 sync point architecture.
protected resources: Resources, local or distributed, that are to be updated (or not updated) in a synchronized and controlled manner, a CRR logical unit of work at a time, through the support of CRR processing (sync point and resynchronization). (The SNA definition of protected resources also includes protected conversations.)
protocol: A set of rules for communication that are mutually understood and followed by two communicating stations or processes. The protocol specifies actions that can be taken by a station when it receives a transmission or detects an error condition.
PS/2: IBM Personal System 2.
PSA: Prefix storage area.
pseudo page fault: A facility available with VM/VS handshaking that lets the VS1 virtual machine dispatch another task while waiting for a page-in request to be completed for some other task. Without this facility, the entire virtual machine would wait until the page request was satisfied, even if higher priority tasks were ready to execute.
pseudo timer: A special VM/ESA timing facility that provides date, time, virtual processor, and total processor time information to a virtual machine.
PSF/VM: Print Services Facility/VM.
PSS: Program support services.
PSU: Product service upgrade.
PSW: Program status word.
PTF: Program temporary fix.
PTF number: A number assigned by service organizations that uniquely identifies a PTF; for example, IBM uses UVnnnnn for a VM-unique product, and UPnnnnn for a cross-system product. PTFs for different products or different releases of a product have different numbers.
PTF parts list: A file that identifies the file name and file type of each part required to install a PTF. A PTF parts list is shipped on the service tape for each PTF on the tape.
PUB: Physical unit block.
PUBLIC: In a file pool, all valid users of the system.
public object: An object that all subjects can access but only trusted subjects can modify. Since all subjects are allowed to access them, public objects must contain innocuous data.
PUT: Program update tape.
PVM: VM/Pass-Through Facility.

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QSAM: Queued sequential access method.
queue: (1) A list constructed and maintained so that the next data element to be retrieved is the one stored first. (T) This method is characterized as first-in-first-out (FIFO). (2) A line or list of items waiting to be processed; for example, virtual machines waiting to run or messages to be displayed. (3) In CMS Multitasking interprocess communication, a list of messages. Synonymous with message queue. (4) To arrange in or form a queue.
queue slice: The maximum amount of time that a virtual machine can stay in the run list.
queue-add: The action by the system scheduler of placing a runnable virtual machine on the list of virtual machines that can be given control of a processor.
queue-drop: The action by the system scheduler of removing a virtual machine from the list of virtual machines that can be given control of a processor.
queue-drop elimination: A VM/ESA performance option that eliminates the dropping of a virtual machine from the run list if the virtual machine is determined to be idle.
queued sequential access method (QSAM): An extended version of BSAM. When this method is used, a queue is formed of input data blocks awaiting processing or processed output data blocks awaiting transfer to auxiliary storage or to an output device.
quiet recording mode: The mode of operation where transient processor or main storage errors corrected or circumvented by hardware RETRY or error correction code logic are not recorded on the VM/ESA error recording cylinders. This mode is entered by the SET MODE RETRY QUIET command or after 12 transient machine checks have occurred while in full-recording mode.

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R/O: Read-only.
R/W: Read/write.
RAS: Reliability, availability, serviceability.
rdev: The real device address of an I/O device.
read authority: The authority to read the contents of a file without being able to change them. For a directory, read authority lets the user view the names of the objects in the directory.
read-only access: An access mode associated with a virtual disk or SFS directory that lets a user read, but not write or update, any file on the disk or SFS directory.
read-only rule: A requirement of a B1 trusted computing base that the security label of the subject dominate that of the object. This prevents a subject from reading up. See also read/write rules, write-only rule.
read-only system residence disk: Synonym for shared read-only system residence disk.
read/write access: An access mode associated with a virtual disk or SFS directory that lets a user read and write any file on the disk or SFS directory (if write authorized).
read/write rules: (1) Requirements in a B1 trusted computing base for a subject's gaining read/write access to a particular object:
reading backward: Reading a file sequentially starting with the last record and working toward the first record. In a file of n records, the first input operation would obtain record n and the last input operation (assuming the entire file is read) would obtain record 1. Backward I/O is only supported for tapes.
reading forward: Reading a file sequentially starting with the first record and working toward the last record. In a file of n records, the first input operation would obtain record 1 and the last input operation (assuming the entire file is read) would obtain record n.
reading up: (1) An event in which a subject with a given security label reads data from an object whose security label dominates that of the subject. A B1 trusted computing base does not allow reading up. (2) Contrast writing down. (3) See also domination rule.
real address: The address of a location in real storage or the address of a real I/O device.
real machine: The actual processor, channels, storage, and I/O devices required for VM/ESA operation.
real system operator: Any user who loads and runs VM in the real machine. Contrast with virtual machine operator.
receive: (1) Bringing into the specified buffer data sent to the user's virtual machine from another virtual machine or from the user's own virtual machine. (2) To load service files from a service tape. (3) In CMS Multitasking interprocess communication, the action of retrieving a message from a queue. (4) See receive message log, receive history log, receive ID, receive status table.
receive history log: A file, $VMFREC $HISTORY, generated by the VMFREC EXEC that lists the CMS files in each tape file loaded from the service tape.
receive ID: A 7- or 8-character alphanumeric identifier that is used to name the software inventory files created during receive processing.
receive message log: A file, in which the VMFREC EXEC writes status and error messages during receive processing.
receive status table: The software inventory table that contains the relationship between a product and the $PPF file used to install it. It also identifies what products of PTFs have been received or committed. The file type of the system level inventory table is SYSRECS and the file type of the service level inventory table is SRVRECS.
recommended service upgrade (RSU) tape: A tape containing preventive service for upgrading the current release of a VM/ESA system once it has been installed.
recomp: To change the number of cylinders/blocks (FB-512 blocks) on the disk that are available to you.
recording mode: See full recording mode, intensive recording mode, or quiet recording mode.
recovery machine: The first machine to join a virtual machine group. It has responsibility for executing routines that were set with the GCS MACHEXT macro and cleaning up system resources when machines leave the group.
recovery server: See CRR recovery server.
register: See general register.
regression: Causing serviced parts to go back to earlier levels. This can occur when applying changes from a PUT to parts updated by corrective service or user modifications.
remote: Two entities (for example, a user and a server) are said to be remote to each other if they belong to different systems within a collection, or to different nodes within an SNA network. Contrast with local.
remote name: In SFS, the name of an entity residing outside a file pool. Within a file pool, remote names are contained in external objects.
remote operator console facility (ROCF): A 4300 Series Support Processor licensed internal code function that permits communication from a remote console for functions like IML or IPL using a switched line. The VM/Pass-Through Facility program provides a communication vehicle that lets any of its supported display stations serve as this remote console.
remote program: The program at the other end of a conversation with respect to the reference program. Contrast with local program.
Remote Spooling Communications Subsystem Networking (RSCS): An IBM licensed program and special-purpose subsystem that supports the reception and transmission of messages, files, commands, and jobs over a computer network.
replacement part: Synonym for serviceable part.
replacement service: Servicing a part by replacing the part with a new one.
reply: (1) A response to an inquiry. (2) In SNA, a request unit sent only in reaction to a received request unit. (3) In CMS Multitasking interprocess communication, the action of sending a response to a message received from a queue.
requester: (1) The name given to a virtual machine containing a user program that requests a resource. (2) The program that relays a request to another computer through the SRPI. Contrast with server.
requisite table: The software inventory table that contains the requisite relationships between products, in the system level, and PTFs in the service level. The file type of the system level inventory table is SYSREQT and the file type of the service level inventory table is SRVREQT.
reserved file types: (1) File types recognized by the CMS editors (EDIT and XEDIT) as having specific default attributes that include record size, tab settings, truncation column, and uppercase or lowercase characters associated with that particular file type. The CMS Editor creates a file according to these attributes. (2) File types recognized by CMS commands; that is, commands that only search for and use particular file types or create one or more files with a particular file type.
reserved page frame performance option: A virtual machine option that reserves a specific number of page frames for one virtual machine. Generally, this option lets the most recently active pages of storage in a virtual machine remain allocated in real storage.
resource: A program, a data file, a specific set of files, a device, or any other entity or a set of entities that the user can uniquely identify for application program processing in a VM system.
resource adapter: Resource manager code that runs in an application's virtual machine. This is the interface between an application program and resource manager. If the adapter represents a resource that is to be protected by the Coordinated Resource Recovery (CRR) facility, then the adapter must register the resource with the sync point manager (SPM), handle various coordination exits that are driven by the SPM, and pass return codes back to the SPM.
resource ID: A one-to-eight character name that identifies a resource.
resource manager: An application running in a server virtual machine that directly controls one or more VM resources. There are four categories of VM resource managers: global, local, private, and system. Also, a resource manager (such as the SFS file pool server), may participate in CRR.
response time: (1) The time between the submission of an item of work to a computing system and the return of results. (2) In systems with time sharing, the time between the end of a block or line-end character of terminal input and the display of the first character of system response at the terminal.
restricted saved segment: A segment space or discontiguous saved segment that can be accessed by a virtual machine only if the directory entry for the virtual machine contains a NAMESAVE control statement that specifies the name of the segment space or discontiguous saved segment.
restricted saved system: A saved system that can be accessed by a virtual machine only if the directory entry for the virtual machine contains a NAMESAVE control statement that specifies the name of the saved system.
Restructured Extended Executor (REXX) language: A general-purpose programming language, particularly suitable for EXEC procedures, XEDIT macros, or programs for personal computing. Procedures, XEDIT macros, and programs written in this language can be interpreted by the REXX/VM interpreter. Contrast with CMS EXEC language and EXEC 2 language.
resync: Resynchronization.
resynchronization: CRR function that is performed by the CRR recovery server when there has been a failure during sync point processing for a transaction. Resynchronization, which involves exchanging log names and comparing logical unit of work states, automatically attempts to complete the sync point process for the transaction. The goal of resynchronization is to maintain a consistent state (data integrity) among the protected resources involved in a transaction. Resynchronization may complete after the application ends. In very rare cases, such as an irrecoverable media
resynchronization initialization: The initial exchange of log names that a participating resource manager initiates with the CRR recovery server before participating in a sync point.
resynchronization recovery: The exchange of log names and compare states flows that the CRR recovery server initiates to ensure consistent completion of a sync point by all protected resources for which data was logged. See also resynchronization.
reverse video: A form of highlighting a character, field, or cursor by reversing the color of the character, field, or cursor with its background.
revoked ALE: The state of a host access-list entry that exists if the entry designates an address space that was subsequently destroyed, or for which the owner has revoked access permission. If a virtual machine attempts to use a host access-list entry that is in the revoked state, an addressing-capability exception is recognized.
revoked alias: An SFS alias that no longer points to a base file because authorization on the base file was revoked from the owner of the alias. Aliases may also be revoked if the storage group in which the alias resides is restored and the base file, which resides in another storage group, does not exist.
REXX exec: An EXEC procedure or XEDIT macro written in the REXX language and processed by the REXX/VM Interpreter. Synonymous with REXX program.
REXX language: Restructured Extended Executor language.
REXX program: Synonym for REXX exec.
REXX/VM: A component of VM/ESA. It contains the REXX/VM interpreter, which processes the REXX language. It also contains the VM implementation of SAA REXX.
REXX/VM Interpreter: The language processor of the VM/ESA operating system that processes procedures, XEDIT macros, and programs written in the REXX language.
ring of files: The arrangement of files in virtual storage when multiple files are being edited by XEDIT.
ROCF: Remote operator console facility.
rollback: (1) In the context of SFS, undoing changes that were made to a resource (such as a file). (2) In the context of CRR, the action taken by CRR for an application program (or transaction program) to initiate CRR backout processing to undo updates to protected resources (such as SFS file pools) during a transaction. See backout.
root process: In CMS Multitasking, a process that performs session initialization and creates a number of threads dedicated to performing standard system functions or managing shared facilities.
rotational position sensing (RPS): A standard or optional feature of most IBM disk storage devices. It lets these devices disconnect from a block-multiplexer channel (or its equivalent on Model 3115/3125 processing units) during rotational positioning operations, thereby letting the channel service other devices.
route: A connection to another system by a logical link and one or more intermediate systems. In TSAF, many links and possible intermediate systems that allow the connection of one system to another.
router: An enhanced connectivity program that interprets requests for services and directs them to the applicable server. See server-requester programming interface (SRPI).
routing table: A CMS file that contains the information that controls the operation of the Programmable Operator Facility. It lets the Programmable Operator Facility recognize a message as a command, determine the action to take when a message comes in, and recognize the authorized users of programmable operator functions.
RPS: Rotational position sensing.
RSCS: Remote Spooling Communications Subsystem Networking.
RSU: Recommended service upgrade
run list: A queue of virtual machines that are executable and currently competing for processor resources. Virtual machines take turns being dispatched for short periods of time (time slices) until they either complete a queue slice or go into a long WAIT state. Virtual machines in the run list can be briefly nonrunnable--for instance, waiting for a page swap--without being dropped from the run list. The virtual machines in the run list are sorted by deadline priority. See eligible list.
RUNNING screen status: For a display terminal used as a virtual console under VM/ESA, an indicator located in the lower right of the screen. It indicates that the user's virtual machine is in control (but not necessarily executing a program or command) and that the terminal can receive messages.

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S-STAT: A block of storage that contains the FSTs associated with the S-disk. The FSTs are sorted so that a binary search can search for files. The S-STAT usually resides in the CMS nucleus so it can be shared. Only files with file mode of 2 will have their associated FSTs in the S-STAT.
SAA: Systems Application Architecture.
SAA Communications Interface: See CPI Communications.
SAA Resource Recovery Interface: The routines that allow applications to initiate a sync point to either commit or back out (roll back) all updates. The SRRCMIT routine commits and the SRRBACK routine backs out the updates. See also CPI Resource Recovery.
SAPL: Stand-alone program loader.
saved segment: An area of virtual storage that is assigned a name and saved. Segment spaces, member saved segments, and discontiguous saved segments are defined by CP and saved in system data files. Logical saved segments are defined by CMS. A saved segment can be attached to and detached from a virtual machine and can be shared by many virtual machines. See segment space, member saved segment, discontiguous saved segment, and logical saved segment.
saved system: (1) The control program portion of an operating system that is assigned a name and saved in pageable format in a system data file. Loading an operating system into a virtual machine by specifying the name of a saved system is more efficient than loading it from a device number. (2) Synonymous with named saved system.
scale: A line on the XEDIT full-screen display, used for column reference.
SCIF: Single console image facility.
SCP: System control programming.
screen: An illuminated display surface; for example, the display surface of a CRT. Synonymous with physical screen.
screen attribute byte: A character position on the screen of a display terminal that defines the characteristics of the next field displayed on the screen; for example, protected, not protected, displayable, or nondisplayable.
screen status area: For a display terminal used as a virtual console under VM/ESA, an indicator of the current status of the display screen. This indicator is located in the lower right of the display screen. See CP READ screen status, HOLDING screen status, MORE screen status, NOT ACCEPTED screen status, RUNNING screen status, and VM READ screen status.
SCRIPT/VS: A component of the IBM Document Composition Facility program product available from IBM for a license fee.
scrolling: (1) Moving a display image vertically or horizontally to view data not otherwise visible within the boundaries of the display screen. (2) Performing a scroll up, scroll down, scroll right, or scroll left operation.
SDB: Structured data base.
SDF: System data file
SDLC: Synchronous data link control.
SDO: System delivery offering.
SECLABEL: Security label.
second-level storage: The storage that appears real to a virtual machine. Contrast with first-level storage and third-level storage.
secondary console image facility: A VM facility that lets console messages and replies be handled by another virtual machine whenever the originating virtual machine is disconnected.
secondary input stream: In CMS Pipelines, (1) an input stream defined for a stage that has a label definition by the first reference to the label or (2) an input stream defined by the ADDSTREAM pipeline subcommand. The secondary input stream has input stream number 1.
secondary output stream: In CMS Pipelines, (1) an output stream defined for a stage that has a label definition by the first reference to the label or (2) an output stream defined by the ADDSTREAM pipeline subcommand. The secondary output stream has output stream number 2.
secondary user: A user designated to receive a disconnected user's console messages and to enter commands to the disconnected user's console.
security category: One of the two components of a security label that specifies which area of information a subject is permitted to access or an object is permitted to contain. See also security level.
security label: A security level and any security categories associated with a subject or object. It is either a precise statement of the level of sensitivity and confidentiality of the contents of an object, or a precise statement of the power and privilege of a subject over objects.
security labeling: Assigning to each subject and object in a system a label denoting security sensitivity. The system uses security labels to enforce mandatory access control.
security level: One of the two components of a security label that specifies into which general class of sensitivity and confidentiality a subject or object falls. See also security category.
segment: (1) An architected segment or saved segment. (2) See discontiguous saved segment (DCSS), exclusive segment, logical saved segment, logical segment definition file, member saved segment, physical saved segment, physical segment definition file, restricted saved segment, segment interface, segment number, segment space, segment table, shared segment, system segment identification file.
segment interface: A method of reading and writing records in which the application is responsible for assembling input segments into logical records and for disassembling logical output records into segments. The segment interface is used under the BSAM and QSAM access methods.
segment number: The part of a virtual storage address needed to refer to a segment.
segment space: (1) A saved segment that begins and ends on a megabyte boundary and contains 1-64 nonoverlapping member saved segments. A segment space is created by CP when member saved segments are defined. Access to a segment space provides access to all of its members. (2) See also discontiguous saved segment, member saved segment, saved segment.
segment table: In System/370 virtual storage systems, a table used in DAT to control user access to virtual storage segments. Each entry indicates the length, location, and availability of a corresponding page table.
select data file: In VMSES/E, a file containing a list of the parts serviced by the VMFAPPLY EXEC. The VMFAPPLY EXEC updates this file with a time stamp and a list of parts that were serviced. The VMFBLD EXEC checks the select data file for build requirements and updates the objects that are affected by service to a status of "SERVICED" in the service-level build status table. The select data file is named appid $SELECT, where appid is the apply ID.
selective line editing: A feature of XEDIT that allows editing of a specified collection of lines while excluding other lines from the screen.
selective preventive service: The selective application of PTFs from a PUT or RSU. Contrast with preventive service.
semaphore: In CMS Multitasking, a variable with an associated wait queue used by threads to control access to a shared resource. CMS Multitasking blocks and unblocks threads on the semaphore's wait queue, but it does not control access to the resource. See also mutex.
separator: Synonym for delimiter.
server: (1) The general name for a virtual machine that provides a service for a requesting virtual machine. (2) The program that responds to a request from another computer or the same computer through SRPI. Contrast with requester. (3) See communications server, CRR recovery server, file pool server machine, intermediate communications server, recovery server, server system, server-requester programming interface (SRPI), trusted server.
server system: A data processing system containing one or more servers providing services in response to a request from another computer.
server-requester programming interface (SRPI): (1) A protocol between requesters and servers in an enhanced connectivity network. Includes the protocol to define a cooperative processing subsystem. (2) The interface that enables enhanced connectivity between requesters and servers in a network.
service: (1) Changing a product after installation. (2) See access method services (AMS), callable services library (CSL), circumventive service, console communication service (CCS), corrective service, corrective service tape, local service, preventive service, program update service, replacement service, selective preventive service, serviceable part, service level, service-level inventory, service machine, service pool, service pool virtual machine, service representative privilege class, service routines, service tape, service virtual machine, serviceability enhancements support stage (SESS), system service program (SSP), system services control point (SSCP), update service, VMSES/E installation/service tool, VTAM service machine (VSM).
service level: The PTF or preventive service level that is associated with the testing level and support level of an orderable product function.
service machine: A virtual machine running a program that provides system-wide services.
service pool: A set of service pool virtual machines, designed to do work with a CMR.
service pool virtual machine: A virtual machine that is one of a set of identical virtual machines, created through the use of the POOL directory statement.
service representative privilege class: The CP privilege class F user, usually an IBM Service Representative, is permitted to set or change the level of detail of I/O device error recording to the level desired. See full recording mode, intensive recording mode, and quiet recording mode.
service routines: CP or CMS routines used for addressing and updating directories; formatting or initializing disks; or doing disk, tape, or terminal I/O functions.
service tape: A tape containing service changes for one or more products. See corrective service tape and program update tape (PUT).
service virtual machine: A virtual machine that provides a system service such as accounting, error recording, monitoring, or that provided by a supported licensed program.
service-level inventory: Synonym for service level software inventory.
service-level software inventory: (1) A file maintained by VMSES/E that shows: requisite relationships between PTFs; the status of the PTFs installed; the level of each part of the product serviced; and the status of objects built for the product. (2) See also system-level software inventory. (3) Synonymous with service-level inventory.
serviceability enhancements support stage (SESS): The component of VM that helps you install and apply service to VM.
serviceable part: (1) In VMSES/E, An individual part of a product that can be serviced separately. A serviceable part has the file name of the source or replacement part and a file type in the form tttnnnnn, where ttt is a unique three-character abbreviation for the part type and nnnnn is the PTF number. Serviceable parts are maintained by both source updates and replacement service. (2) Contrast with usable part. (3) Synonymous with replacement part.
session: (1) The SNA term for a connection between two LUs. The LUs involved allocate conversations across sessions. (2) In CMS Multitasking, the processes, accessible devices, and addressable storage associated with a virtual machine. (3) See session limits, terminal session.
session limits: The maximum number of sessions that can occur between a pair of LUs.
SET ADDRESS SPACE CONTROL (SAC): An instruction that modifies the translation mode in which a virtual machine is operating. For XC virtual machines, the SET ADDRESS SPACE CONTROL instruction can be used to switch between the primary-space and access-register modes.
sever: (1) Ending communication with another virtual machine or with the user's own virtual machine. (2) In CMS Pipelines, to cause a stream to become unconnected.
SFS: Shared file system.
SFS communication adapter: The part of CMS in a user machine that communicates with file pool server machines.
SFS directory: A group of files. SFS directories can be arranged to form a hierarchy in which one directory can contain one or more subdirectories as well as files.
shadow page table: A page table that CP creates and uses to control the virtual storage of a virtual machine operating system (such as DOS/VS or OS/VS) that itself can perform paging on a real machine.
shared file system (SFS): A part of CMS that lets users organize their files into groups known as directories and selectively share those files and directories with other users.
shared read-only system residence disk: A system residence disk tailored so that most of the system residence information is read-only and accessible to all relevant virtual machines, leaving a relatively smaller private read/write system disk that must be dedicated to each virtual machine. This technique can substantially reduce the disk requirements of an installation by avoiding needless duplication of disk packs by virtual machines that use the same operating system. See saved system. Synonymous with read-only system residence disk.
shared segment: One or more segments of real storage, saved in a saved system, member saved segment, or discontiguous saved segment, that can be shared among many virtual machines. For example, in a CMS saved system, the CMS nucleus is shared in real storage by all virtual machines that loaded CMS by name; that is, every CMS virtual machine maps a 1MB segment of virtual storage to the same 1MB of real storage.
shared system: See saved system and shared read-only system residence disk.
short: (1) In CMS Pipelines, to cause a stream to bypass a stage by connecting the output of the preceding stage to the input of the following stage. The shorted stage can neither read from the input stream nor write to the output stream. (2) In CMS Pipelines, a bypass made by shorting.
SID code: Support Identification code.
side information: System-defined values that are used for the initial values of the partner_LU_name, mode_name, and TP_name conversation characteristics, among others. VM implements side information in CMS communications directory files.
signal: (1) An information packet that indicates the occurrence of an event. (2) To announce that an event has occurred.
signaling attention: An indication that a user has pressed a key or entered a CP command to present an attention interrupt to CP or to the user's virtual machine.
simultaneous peripheral operations online (SPOOL): (1) (Noun) An area of auxiliary storage defined to temporarily hold data during its transfer between peripheral equipment and the processor. (2) (Verb) To use auxiliary storage as a buffer storage to reduce processing delays when transferring data between peripheral equipment and the processing storage of a computer.
single console image facility (SCIF): (1) Lets a user, who is disconnected from a primary virtual console, continue to have console communications by way of the console of the secondary user. See secondary user. (2) Enables a virtual machine operator to control multiple virtual machines from one physical terminal.
single key protection: This program support associates each 4K block of real storage with one storage key. Only one key is needed to protect a 4K frame.
single key storage: Real storage composed of storage frames that are protected by one storage key per 4K frame rather than two storage keys per 4K frame.
single processor mode: In tightly coupled MP or AP systems, single processor mode lets an installation dedicate a processor to an MVS V=R virtual machine. In single processor mode, VM/ESA runs in uniprocessor mode in the main processor, and the MVS V=R virtual machine runs under VM/ESA in the main processor and has the exclusive use of the other processor for MP or AP operations. However, other virtual machines can operate under VM/ESA concurrently with the MVS V=R virtual machine in single processor mode (not to be confused with uniprocessor mode).
single user group: The concept in GCS of a virtual machine that runs applications that do not require group communications. This allows an application to run without the overhead of group initialization and multiple virtual machines. Multiple users can IPL the same saved system if it had been built for a single user environment. See virtual machine group.
single-density DASD volume: A DASD volume with the standard number of cylinders for its device type, for example, a 3380-D or 3380-J with 885 cylinders, or a 3390-1 with 1113 cylinders. See double-density DASD volume and triple-density DASD volume.
sink virtual machine: In VMCF, the virtual machine that receives messages or data from a source virtual machine. Contrast with source virtual machine.
SIO: Start I/O.
sleep mode: A mode in which the virtual machine is in a dormant state; that is, the virtual machine is not running, but connect time still accumulates, and messages can be displayed at the terminal. The virtual machine is restarted either at the end of a specified interval or when the user signals attention to CP. See signaling attention.
slot sorting: A technique the CP paging supervisor uses to reduce the number of separate channel programs needed to read pages from or write pages on a paging device. This is done by grouping, in the same channel program, the reading or writing of pages that occur in different relative record positions on the same track or within the same cylinder.
smoothed data: Statistical data (as in a curve or graph) freed from irregularities by ignoring random occurrences or by a process of continual averaging.
SMSG function: A CP function that lets a virtual machine send a special message to another virtual machine programmed to accept and process the message. See also special message.
SNA: Systems Network Architecture.
SNA/CCS terminal: Any terminal accessing VM that is managed by a VTAM service machine.
software inventory: See service-level software inventory, system-level software inventory, software inventory management.
software inventory management: Utilities provided by VMSES/E that provide a standard interface to the system-level inventory, service-level inventory, tool control statements (TCS), product parameter file (PPF), and file type abbreviation table.
software product: Any software supplied by IBM or an Original Equipment Manufacturer (OEM), or user written programs. The term includes program offerings and program products (PPs).
software vendor: A variety of application developers that includes, but is not limited to, Value-Added Dealers (VADs), Value-Added Remarketers (VARs), and Third Party Programmers (TPPs).
source code: The input to a compiler or assembler, written in a source language. Contrast with object code.
source file: A file that contains source statements for such items as high-level language programs and data description specifications.
source product parameter file: In VMSES/E, a file supplied with a product containing recommended values for the options that control VMSES/E processing for the product, formats of installation and service tapes, and the list of build lists used to build the product. The file name is the ID of the product and the file type is $PPF.
source update: A change to the original assembler code provided with a product. VM source code is contained in files with a file type of ASSEMBLE. To update an ASSEMBLE file, the user creates update files containing control statements that describe the changes to be made.
source update file: A file containing a single change to a statement in a source file. The file can also include requisite information for applying the change. Synonymous with update file.
source virtual machine: In VMCF, the virtual machine that initiates the sending of messages or data to another virtual machine. Contrast with sink virtual machine.
spanned record: A logical record that spans across one or more data blocks on a storage device.
sparse block: Data blocks or pointer blocks that contain all binary zeros and are not physically stored in a file. Do not write programs that depend on sparse files because the CMS file system handling of sparse blocks may change.
sparse record: For files with fixed-length records, a record written with a position number more than one greater than the number of the last record. For example, if the last record in the file, DOG DATA, has a position number of 55, you can write a record with a position number of 60. Records 56, 57, 58, and 59 are the sparse records. Sparse records are not written to a file. If you try to read a sparse record, it will be retrieved asX'00' bytes. See logically sparse file.
special message: A data transmission, made up of instructions or commands, sent from one virtual machine to another by means of the SMSG function. A special message is processed by the receiving virtual machine and does not appear on the receiver's console. See also SMSG function.
special variable: A reserved variable name assigned a value during processing by the REXX Interpreter, the EXEC 2 processor or CMS EXEC processor. These variables can be tested within an EXEC procedure, edit macro, or XEDIT macro.
SPF: Storage protect feature.
SPM: Synchronization point manager
SPOOL: Simultaneous peripheral operations online.
spool file: A collection of data along with CCWs for processing on a unit record device. Contrast with system data file.
spool file block: A 4096-byte buffer that contains control information, in addition to records. Synonymous with spool file buffer linkage block.
spool file buffer linkage block: Synonym for spool file block.
spool file class: A one-character class associated with each virtual unit record device. For input spool files, the spool file class lets the user control which input spool files are read next; and, for output spool files, it lets the spooling operator better control or reorder the printing or punching of spool files having similar characteristics or priorities. The spool file class value can be A through Z or 0 through 9.
spool file tag: In VM/ESA, a 136-character data field associated with each output spool file generated. The use, content, and format of this field is a bilateral decision between the originator and receiver of the file.
spool ID: A spool file identification number automatically assigned by CP when the file is closed. The spool ID number can be from 0001 to 9900; it is unique for each spool file. To identify a given spool file, a user must specify the owner's user ID, the virtual device type, and the spool ID.
spooling: The processing of files created by or intended for virtual readers, punches, and printers. The spool files can be sent from one virtual device to another, from one virtual machine to another, and to real devices. See virtual console spooling.
spooling area: Any direct access storage area that VM/ESA temporarily uses to store input for a virtual card reader, output for a virtual printer or punch, or a console log of I/O for a virtual console.
spooling devices: I/O devices (card readers, punches, printers, DASD) that read input and write output.
spooling operator privilege class: The CP privilege class D user who controls the real unit record equipment and all closed spool files.
spooling unit record I/O: See spooling and virtual spooling device.
SR: Symptom record.
SRPI: Server-requester programming interface.
SSCP: System services control point.
SSP: System service program.
stable access: The data on the minidisk will remain unchanged by others until the person holding the stable read or write releases access.
stack: See console stack and program stack.
stage: (1) In CMS Pipelines, a program or a label reference in a pipeline. A pipeline consists of one or more stages, delimited by stage separators. (2) See also device driver, filter. (3) See built-in stage command, stage command, stage separator, user-written stage command.
stage command: (1) In CMS Pipelines, a command that manipulates data, reads data from a device or host interface, or writes data to a device or host interface. (2) See also filter, device driver. (3) See built-in stage command, user-written stage command.
stage separator: In CMS Pipelines, a character that indicates the end of one stage of a pipeline and the beginning of the next stage. The default stage separator is the solid vertical bar (|).
stall: In CMS Pipelines, a condition in a multistream pipeline in which no stage can run.
stand-alone: An operation independent of another device, program, or system. See online test stand-alone executive program (OLTSEP), stand-alone dump, stand-alone program, stand-alone program loader (SAPL).
stand-alone dump: A dump acquired without regular system functions. For example, to obtain a CP dump when the regular system is unable to dump the machine, the stand-alone dump facility gets a CP stand-alone dump.
stand-alone program: A program independent of any other program or system.
stand-alone program loader (SAPL): A program installed in cylinder 0 of a disk volume. The stand-alone loader is a generic loader that can load any program designed to work with it.
standard CMS multivolume support: Refers to the CMS support of tape switching. For this support, CMS does all necessary volume label processing. All volume switching is performed by either the default CMS volume switching routine (DMSTVS) or the DMSTVI tape label processing exit (if one has been provided by the user or installation).
state: See program state.
state transition: The change from one program state to another in a conversation.
static CP area: The portions of virtual storage allocated to CP during system generation and IPL.
status area: The area in the bottom right corner of the screen that contains messages about the status of a virtual machine.
storage control: The component in a DASD subsystem that connects the DASD to the host channels. It does channel commands and controls the DASD devices.
storage group: A subset of minidisks within a file pool. Each storage group is identified by a number.
storage group 1: See catalog storage group.
storage key: An indicator associated with one or more storage blocks that requires that tasks have a matching protection key to use the blocks.
storage levels: See first-level storage, second-level storage, and third-level storage.
stream: (1) In CMS Pipelines, a flow of data records into a stage or out of a stage. One end of a stream enters or leaves a stage. The other end can be connected to streams of other stages so that data can flow between stages. A stage's input and output streams are numbered separately, starting at zero. Streams can also be given an identifier. (2) See input stream, multistream pipeline, output stream, primary input stream, primary output stream, secondary input stream, secondary output stream, stream identifier, tertiary input stream, tertiary output stream.
stream identifier: In CMS Pipelines, a symbolic name for a stream, consisting of a period, one to four alphabetic characters, and a colon.
string: A group of minidisks defined for a specific function in the product parameter file, for example, the BASE2 string, which holds source code.
structurally sparse files: Files that contain sparse blocks. See sparse block.
subcommand: The commands of processors such as EDIT or XEDIT that run under CMS.
subdirectory: Any SFS directory below a user's top directory. The CREATE DIRECTORY command creates subdirectories. There can be up to eight levels of subdirectories with no limit on the number of them at each level, other than overall DASD space limits. Each level of a subdirectory is an additional identifier of up to 16 characters that is appended to next higher level subdirectory.
subject: In computer security, an active entity that causes information to flow among objects or changes the system's state. A subject is generally a person, process, or device. Contrast object.
subroutine pipeline: In CMS Pipelines, the operand of the CALLPIPE pipeline subcommand.
supersede: Of a PTF, to include all the APARs, parts, and requisite relationships of another PTF.
supervisor call instruction (SVC): An instruction that interrupts a program being executed and passes control to the supervisor so that it can do a specific service indicated by the instruction.
supervisor state: A state during which the processor can execute I/O and other privileged instructions. Only CP can execute in the supervisor state; all virtual machine operating systems run in problem state. Contrast with problem state.
SVC: Supervisor call instruction.
SVC 76 error recording interface: A means for VM/ESA to record the error incidents met by certain operating systems running in a virtual machine under VM/ESA. When the virtual operating system issues SVC 76, VM/ESA translates the virtual storage and I/O device addresses to the real ones, records the information on the VM/ESA error recording cylinder, and returns control to the virtual machine; thus bypassing the virtual machine's own error recording routine and avoiding duplicate recording of the same errors.
symbolic destination name: A name an APPC/VM or CPI-Communications connection uses. Symbolic destination names index SNA routing and security parameters, which are stored in communications directory NAMES files, to complete a connection.
sync point: See synchronization point processing.
sync point manager: Synchronization point manager.
sync point processing: Synchronization point processing.
sync point tree: A conceptual structure used to organize all the protected resources and protected conversations that are coordinated by a SPM in a transaction. The tree consists of nodes that contain the protected resources and nodes that are the targets of protected conversations.
synchronization point manager (SPM): The part of the Coordinated Resource Recovery (CRR) facility that resides in the application's virtual machine. A protected resource registers with the SPM to participate in CRR. The SPM coordinates the updating of protected resources and distributes the coordination of protected conversations to other SPMs.
synchronization point processing: Consists of the SPM driving the participating resource adapters through the following SPM exits:
synchronous communication: A method of communication in a conversation where a user's virtual machine is put in a WAIT state and cannot issue any communication functions on any conversations until a particular function completes.
synchronous data link control (SDLC): A data link over which communication is conducted using the synchronous data protocol.
synchronous processing for DASD: Channel data is transferred for each system channel operation when the target data field passes the read/write head on the device.
synonym: In CMS, an alternative command name defined by the user as equivalent to an existing CMS command name. Synonyms are entries in a CMS file with a file type of SYNONYM. Entering the SYNONYM command allows use of those synonyms until that terminal session ends or until the use of synonyms is revoked by entering the SYNONYM command with no operands.
syntax: The rules for the construction of a command or program.
SYSGEN: System generation
SYSHIGH: The security label associated with the most important and most sensitive data handled by a given B1 trusted computing base. It is a security label combining the system's highest security level with all of the system's security categories. Contrast SYSLOW.
SYSLOW: The security label associated with the least important and least sensitive data handled by a given B1 trusted computing base. It is a security label consisting of the system's lowest security level with none of the system's security categories. Contrast SYSHIGH.
system administrator: The person responsible for maintaining a computer system.
system analyst privilege class: The CP privilege class E user, usually the VM/ESA system analyst, who can query, examine, and print or display, but not change, certain areas of the CP nucleus and can create saved systems.
system configuration file: A file that resides on the parm disk and contains information about how CP should initialize the system.
system control file: In CP, the file that consists of macroinstructions that describe the CP system residence disk, the real main storage size, the CP-owned DASD volumes, the VM/ESA system operator's user ID, and the system timer value.
system control programming (SCP): IBM-supplied programming fundamental to the operation and maintenance of the system. It serves as an interface with IBM licensed programs and user programs and is available without additional charge.
system data file (SDF): A file defined by CP to hold a collection of data associated with a particular system function, such as a saved segment, a saved system, a printer image library, user class restructure definitions, a message repository, or system trace data. Because a system data file contains no CCWs, it cannot be processed on a unit record device. Contrast with spool file.
system DDR tape: A tape containing the image of a built system for various types of DASD.
system delivery offering (SDO): A VM/ESA package that includes a subset of all VM products or components. This package has a single point of order and delivery, is refreshed periodically, and is installed from one logical tape. All products or components included with the package, and their requisite relationships, are tested to ensure the package functions as a system.
system disk: In VMSES/E, a minidisk or SFS directory containing the other products that are required during service.
system event: In CMS Multitasking, an event defined and signaled by CMS. See also event.
system gateway: A gateway that lets APPC programs access global or private resources on a specific system within a CS or TSAF collection. APPC programs in a TSAF collection can also use the system gateway to access resources from an adjacent CS collection. Similarly, an APPC program in a CS collection can access resources in an adjacent TSAF collection. Contrast with global gateway and private gateway.
system generation (SYSGEN): The process of selecting optional parts of an operating system and of creating a particular operating system tailored to the requirements of a data processing installation. (I) (A)
system integrity: The property of a system that is designed, implemented, and maintained to protect itself from unauthorized access.
system load: The combination of active devices, programs, and users that use the system resources of the processor and storage.
system name table: In CP, the table that contains the name and location of saved systems, including shared and nonshared segments.
system object: An object, such as a saved segment, that may contain objects or parts supplied by more than one component or product.
System Offering: A package containing VM/SP and associated products.
system profile: An EXEC (SYSPROF) that resides in a saved system or on a system disk and called by CMS initialization. It contains some initialization functions, and provides a means for installations to override the default CMS environment by tailoring the exec to suit the installation.
system programmer privilege class: The CP privilege class C user; usually, the VM/ESA system programmer, who can change the contents of any real storage locations in the machine.
system residence volume: The volume from which the nucleus of the operating system is read during IPL.
system resource: A resource that is unique on the system on which it is defined (similar to a local resource) but is accessible (similar to a global resource) from remote systems in a CS or TSAF collection, or in the SNA network. Contrast with local resource, global resource, and private resource.
system resource manager: An application that runs in a server workstation or virtual machine and provides a service for connecting programs. The system resource identified is not known globally throughout the TSAF or CS collection. However, by specifying the system gateway name of the system on which the system resource manager resides, APPC programs within the collection can access the system resource. Contrast with global resource manager, private resource manager, and local resource manager.
system resource operator privilege class: The CP privilege class B user, who controls all the real resources of the machine, such as real storage, disk drives, and tape drives, not controlled by the primary system or spooling operators.
system restart: The restart that allows reuse of previously initialized areas. System restart usually requires less time than IPL. See warm start.
system segment identification file: A file (SYSTEM SEGID) that identifies the logical saved segments on the system and the physical saved segments in which they reside.
system service program (SSP): In ACF/TCAM, an IBM-supplied or user-supplied program that does system-oriented auxiliary functions in support of the message control program. System service programs run under control of the initiator as attached subtasks.
system services control point (SSCP): In SNA, the focal point within an SNA network for managing the configuration, coordinating network operator and problem determination requests, and providing directory support and other session services for end users of the network.
system string: In VMSES/E, the set of system disks.
system trace file: A type of system data file that contains CP or virtual machine trace data.
system-level inventory: Synonym for system-level software inventory.
system-level software inventory: (1) A file maintained by VMSES/E that contains requisite relationships between products or components; mapping of product identifier to the name of the $PPF file used during installation; the status of the product or component on the system; and mapping of PTF file type abbreviation to real CMS file type. (2) See also service-level software inventory. (3) Synonymous with system-level inventory.
Systems Application Architecture (SAA): A defined set of interfaces, conventions, and protocols that can be used across various IBM systems.
Systems Network Architecture (SNA): The description of the logical structure, formats, protocols, and operational sequences for transmitting information units through and controlling the configuration and operation of networks.

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T-disk: Synonym for temporary disk.
tailorable file: Any source level product file that requires user input in order for the product to work correctly. (An example is a PROFILE EXEC.)
tape descriptor file: A file containing a directory of the products on a service tape.
tape document: A document describing the service procedure for a service tape.
target: (1) One of many ways to identify a line to be searched for by XEDIT. A target can be specified as an absolute line number, a relative displacement from the current line, a line name, or a string expression. (2) In CMS Pipelines, a way to identify a record to be searched for. A target can be a group of characters, a delimited string, a number of records, or a displacement value.
target disk: In VMSES/E, a minidisk or SFS directory on which are received tape files from which the objects are built.
target string: In VMSES/E, the set of target disks.
task: A basic unit of work used for the execution of a program or a system function.
task ID: A 2-byte field that uniquely defines a task within a GCS virtual machine. Task ID is sometimes combined with machine ID to uniquely identify a task within a virtual machine group.
TCB: Trusted computing base.
TCS: Tool control statement.
template file: A file that defines the number, data type, and length of parameters that a CSL routine expects.
temporary disk: An area on a DASD available to the user for newly created or stored files until logoff, at which time the area is released. Temporary disk space is allocated to the user during logon or when entering the CP DEFINE command. Synonymous with T-disk.
temporary product parameter file: In VMSES/E, the output of the VMFOVER EXEC. The file name is either the file name of the last override product parameter file in the chain of overrides, or the file name of the source product parameter file. The file type is $PPFTEMP.
terminal: (1) A device, usually equipped with a keyboard and a display, capable of sending and receiving information. (2) See control terminal, control unit terminal (CUT), display terminal, distributed function terminal (DFT), logically connected terminal, SNA/CCS terminal, terminal input buffer, terminal session, terminal user, typewriter terminal.
terminal input buffer: Holds lines entered at the user's terminal until CMS processes them.
terminal session: The time from logon to logoff when a user and the virtual machine can use the facilities of VM/ESA or the operating system or both. This also includes any time that the virtual machine is running in disconnect mode. See disconnect mode.
terminal user: Anyone who uses a terminal to log on to VM/ESA.
tertiary input stream: In CMS Pipelines, (1) an input stream defined for a stage that has a label definition by the second reference to the label or (2) an input stream defined by the ADDSTREAM pipeline subcommand. The tertiary input stream has input stream number 2.
tertiary output stream: In CMS Pipelines, (1) an output stream defined for a stage that has a label definition by the second reference to the label or (2) an input stream defined by the ADDSTREAM pipeline subcommand. The tertiary output stream has output stream number 2.
text deck: An object-code file that must be additionally processed to produce executable machine code.
text library: A CMS file that contains relocatable object modules and a directory that indicates the location of each of these modules within the library.
text shell: A file that contains prologue information for a text deck but no additional code.
third-level storage: The virtual storage created and controlled by an OS/VS or VM virtual machine. Contrast with first-level storage and second-level storage.
thread: In CMS Multitasking, the basic dispatchable entity in the system. It is an instance of execution of a unit of program code; its environment is characterized by a PSW, a set of register values, and a save area stack.
time share: To use a device or system for two or more interleaved purposes.
time sharing: A method of using a computing system that lets many users execute programs concurrently and interact with the programs during execution.
time stamp: A record containing the TOD clock value stored in its internal 32-bit binary format.
time-of-day (TOD) clock: A hardware feature required by VM/ESA. The TOD clock is incremented once every microsecond, and provides a consistent measure of elapsed time suitable for the indication of date and time; it runs regardless of the processor state (running, wait, or stopped).
time-out, logon: For a terminal attempting to log on to VM/ESA, through a switched line, the Line Timeout hardware feature of a telecommunications control unit that logs off the user if characters are not entered for a specified time, usually 28 seconds. If logged off, the user must dial the VM/ESA computer again.
TOD clock: Time-of-day clock.
token: An eight-character symbol created by the CMS EXEC processor when it scans an EXEC procedure or EDIT macro statements. Symbols longer than eight characters are truncated to eight characters.
token ring network (TRN): A network that uses a ring topology, in which tokens are passed in the circuit from node to node. A node ready to send can capture the token and insert data for transmission.
tokenized PLIST (parameter list): A string of doubleword aligned parameters occupying successive doublewords.
tool control statement (TCS): Statements used for product or component installation and for a PTF. The TCS data for product installation is supplied by the product owner or product packager on the product install tape. The TCS data for PTFs is supplied by the product's local control group (LCG).
top directory: The directory created for a user when the user is enrolled in a file pool. The name of the top directory is the same as the person's user ID.
topmost window: With the window support, the highest window in the display order such that: (1) The window name is not WM or STATUS. (2) The window currently displays at least one virtual screen data line or reserved line. For example, a vsize window connected to a virtual screen such that there are no scrollable data being displayed, is NOT the topmost window.
total CPU time: The virtual processor time plus the CP overhead to service the virtual machine.
TPN: Transaction program name.
trace table: Synonym for CP trace table.
transaction: See logical unit of work (in terms of CRR) or LUWID.
transaction program: (1) An application that runs within a particular LU. Within an SNA-defined network, a resource in a VM/ESA system, in a CS or TSAF collection is viewed as a transaction program within the LU that represents the VM/ESA system, CS collection, or TSAF collection. (2) In the context of CRR, an application program that executes one or more transactions or CRR logical units of work.
transaction program name (TPN): A symbolic name given to a particular transaction program in an SNA-defined network.
transient program area: In CMS, the virtual storage area occupying locations X'E000' to X'10000'. Some CMS commands and user programs execute in this area of CMS storage.
transition: See state transition.
translate mode: The operating mode of a virtual machine when virtual addresses are converted to real addresses by segment and page tables.
transparency mode: A BSC mode that permits transmission of any data, bypassing regular BSC control character scanning.
Transparent Services Access Facility (TSAF): A component of VM/ESA that handles communication between systems by letting APPC/VM paths span multiple VM systems. TSAF lets a source program connect to a target program by specifying a name that the target has made known, instead of specifying a user ID and node ID.
triple-density DASD volume: A DASD volume with three times the standard number of cylinders for its device type, for example, a 3380-K with 2655 cylinders. See single-density DASD volume and double-density DASD volume.
TRN: Token ring network.
truncation: A valid shortened form of CP, CMS, GCS, Dump Viewing Facility, RSCS, TSAF (Query only) command names, operands, and options that can be entered. When the shortened form is used, the number of key strokes is reduced. For example, the ACCESS command has a minimum allowable truncation of two, so AC, ACC, ACCE, ACCES, and ACCESS are all recognized by CMS as the ACCESS command. Contrast with command abbreviation.
truncation setting: In the CMS Editor, the value that determines the maximum length of input lines.
trusted computing base (TCB): In computer security, all of the protection mechanisms within a computer system, including hardware, software, and firmware, the combination of which enforces a security policy. It creates a basic protection environment and provides additional user services required for a trusted computer system.
trusted server: A machine that runs programs necessary to the system's operation. (These programs provide services such as accounting, error recording, security, network management, printing, and many others.) A trusted server always runs disconnected, and it never performs work on behalf of some other user. Though not all servers are privileged, most are able to issue CP privileged commands.
TSAF: Transparent Services Access Facility.
TSAF collection: A group of VM processors, each with a TSAF virtual machine, connected by CTC, binary synchronous lines, or LANs.
TSAF virtual machine: The virtual machine that lets user programs connect to and communicate with virtual machines on different VM systems.
TSAF VTAM line driver: A portion of TSAF that handles APPC communications across VTAM-controlled links.
two-phase commit protocol: The method that permits updates to distributed protected resources to be committed or rolled back atomically. In the first phase the initiator requests that all participating resource managers vote whether the transaction should be committed or rolled back. All participating resource managers must vote to commit if the transaction is to be committed. When all the votes are collected and the initiator's decision is recorded on the CRR logs, then the second phase begins. The initiator informs the participating resource managers to commit or roll back. At various times, state information is written to the CRR logs so that the distributed resources can be resynchronized if there are any failures during the two-phase commit processing. The two-phase commit is implemented during CRR's coordination function and is part of the LU 6.2 sync point architecture.
two-word command: A command resolved to a program name by using the first two tokens of its tokenized parameter list.
typewriter terminal: Printer-keyboard devices that produce hardcopy output only, such as the IBM 2741 Communication Terminal; the IBM 3215 Console Printer-Keyboard; or the IBM 3767 Communication Terminal, Model 1 or 2, operating as a 2741. This term also refers to the IBM 3101 Display Terminal operating as a 2741.

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UCR: User class restructure.
UCS: Universal character set.
uncommitted work: Operations associated with a work unit that have not yet been committed or rolled back.
uniprocessor mode: This term indicates that there is only one processor in the physical configuration, or that VM/ESA uses the facilities of one processor in an AP or MP system (not to be confused with single processor mode).
unit record device: A reader, a printer, or a punch.
universal character set (UCS): A printer feature that permits a variety of character arrays. Synonym for printer universal character set.
universal class card reader: A virtual card reader that can read any class of reader, printer, or punch files spooled or transferred to it.
untokenized parameter list: A parameter list in which no restrictions are placed on the structure of the items in the list. See token and tokenized PLIST (parameter list).
unused ALE: The state of a host access-list entry that exists when the entry does not designate an address space. If a virtual machine attempts to use a host access-list entry that is in the unused state, an ALEN-translation exception is recognized.
update file: Synonym for source update file.
update number: A number assigned by service organizations and uniquely associated with a PTF. The PTF number and update number can be the same. If they are different, there is a one-to-one correspondence between the PTF number and the update number. With VM/ESA source-maintained products, only one APAR is fixed in each PTF, and the PTF number is not the same as the update number. The update number format is raaaaacc, where r identifies the product and release, aaaaa is the APAR number, and cc defines the component.
update service: Servicing a part by applying a change to a source file statement, then assembling or compiling the source file to produce a new object file.
update shell: A file that contains requisite information for applying an update but does not contain the update code.
UPSI: User program switch indicator.
usable form: (1) A built part of a product. The service level of a usable form cannot be determined from the file identifier, for instance an exec file with the file type of EXEC. See usable form product parameter file. (2) See also serviceable part, base file type.
usable form product parameter file: In VMSES/E, a product parameter file produced by applying all override product parameter files to a source product parameter file, and used by most VMSES/E execs during installation. The file name is either the file name of the last override product parameter file in the chain of overrides, or the file name of the source product parameter file if there are no overrides. The file type is PPF.
user: (1) Anyone who requests the services of a computing system. (2) See authorized user ID, class A user, class Any user, class B user, class C user, class D user, class E user, class F user, class G user, CMS user disk, general user privilege class, installed user program (IUP), inter-user communication vehicle (IUCV), interactive user, memo-to-users, multiple user mode, noninteractive user, secondary user, single user group, terminal user, user class, user class restructure (UCR), user data, user exit, user ID, user identification card, user input area, user memo, user modification, user profile table, user program, user program area, user program switch indicator (UPSI), user-written CMS command, user-written stage command.
user class: A privilege category assigned to a virtual machine user in the user's directory entry; each class specified allows access to a logical subset of all the CP commands. See privilege class.
user class restructure (UCR): The extension of the class structure of CP instructions from 8 to 32 classes for each user, command, and DIAGNOSE code within the system. This extension allows the installation greater flexibility in authorizing CP instructions.
user data: In a file pool, any data that resides in storage groups 2 through 32767.
user exit: An interface to VM/ESA that can be used by an application program. Generally, a user exit affects only the particular application specifying the exit and is run as part of the application program.
user ID: User identification.
user identification card: See ID card.
user input area: On a display device, the lines of the screen where the user is required to enter command or data lines. See display mode, input line, and line mode.
user memo: (1) At the system-level, special instructions for installing a product. (2) At the service-level, special instructions for installing a PTF. (3) memo-to-users.
user modification: Any change that a user originates for a product or component. See also local service.
user profile table: A table of user attributes (called virtual machine control block (VMBLOK)) built for each active user from information gathered during logon.
user program: A transaction program that requests a service from a resource manager program. User programs reside in requester virtual machines.
user program area: In CMS, the virtual storage area occupying location X'20000' to the end of the user's virtual machine. The beginning of the user program area is the default loading point for user programs and for many CMS commands.
user program switch indicator (UPSI): An operand of the CMS SET command. The user can set the switches (1 byte) to a desired value, which can be tested by a program in CMS/DOS.
user-written CMS command: Any CMS file created by a user that has a file type of MODULE or EXEC. Such a file can be executed as if it were a CMS command by issuing its file name, followed by any operands or options expected by the program or EXEC procedure.
user-written stage command: (1) In CMS Pipelines, a stage command that is not supplied by CMS Pipelines. A user-written stage command is written in REXX; can contain pipeline subcommands, REXX instructions, and host commands; and has a file type of REXX or is called with the REXX stage command. (2) See also built-in stage command.

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V=F machine: Virtual=fixed machine.
V=R: Synonym for virtual=real option.
V=R area: Virtual=real area.
V=R machine: Virtual=real machine.
V=R machine recovery: Virtual=real machine recovery.
V=V machine: Virtual=virtual machine.
vaddr: Virtual address.
valid ALE: The state of a host access-list entry that exists when the entry designates an address space and access permission for the space is still in effect. A valid host access-list entry can be used to access the subject address space when in access-register mode.
variable symbol: In an EXEC procedure, a symbol beginning with an ampersand (&) character, the value of which is assigned by the user, or sometimes by the VM/REXX interpreter, the EXEC 2 processor, or CMS EXEC processor. The value of a variable symbol can be tested and changed using control statements. See special variable.
VCIT: Virtual configuration identification token.
Vector Facility (VF): A hardware feature that provides synchronous instruction processing for high-speed manipulation of fixed-point and floating-point data.
verification setting: When using the CMS Editor or XEDIT, the verification setting determines whether new lines entered, or the results of editing changes entered by the user, are displayed at the user's terminal.
version vector table: The software inventory table that identifies which PTFs have been applied to each part of the product and the current level of each part. The file type of the service level inventory table is VVTlvlid. The lvlid may be unique for each level of service the customer has installed for a product or component. It corresponds directly to each AUX level in the control file. The system level inventory does not contain this table.
VF: Vector Facility.
virtual address: The address of a location in virtual storage. A virtual address must be translated into a real address to process the data in processor storage.
virtual block multiplexer mode: A virtual machine option that allows the interleaving of data to different virtual devices on the same virtual channel path.
virtual card reader: CP's simulation on disk of a real card reader. A virtual card reader can read card, punch, or print records of up to 151 characters in length. The virtual device type and I/O device address are usually defined in the VM/ESA directory. See spool file class and universal class card reader.
virtual configuration identification token (VCIT): An 8-byte token that uniquely identifies a particular virtual machine. The VCIT is a system-wide, unique identification token--once a VCIT value has been assigned to a virtual machine, that VCIT value is not used again within the scope of a VM/ESA IPL (CP IPL). The VCIT for a virtual machine is equal to the ASIT that identifies the virtual machine's host-primary address space.
virtual console: A console simulated by CP on a terminal such as a 3270. The virtual device type and I/O address are defined in the VM/ESA directory entry for that virtual machine.
virtual console function: A CP command that the Diagnose Interface executes.
virtual console spooling: The writing of console I/O on disk as a printer spool file instead of, or in addition to, having it typed or displayed at the virtual machine console. The console data includes messages, responses, commands, and data from or to CP and the virtual machine operating system. The user can invoke or terminate console spooling at any time. When the console spool file is closed, it becomes a printer spool file. Synonymous with console spooling.
virtual CPU time: The time required to execute the instructions of the virtual machine.
virtual disk: (1) A logical subdivision (or all) of a physical disk storage device that has its own address, consecutive storage space for data, and an index or description of the stored data so that the data can be accessed. (2) A virtual disk is also called a minidisk.
virtual disk initialization program: The program that can initialize virtual as well as real disks for use by VSE, and OS/VS virtual machines running under VM/ESA. See device support facilities. Contrast with format program.
virtual file: (1) A file or data set residing at a remote computer being used as though it were residing at the local computer (for example, an IBM host computer file being used from a PC as though it were a PC file). (2) An agent that transforms a request for a DOS file to a request for a VM or MVS System/370 file and lets the user access the file as if it were a PC file.
virtual interval timer assist: A hardware assist function, available only on a processor, that has ECPS. It provides, if desired, a hardware updating of each virtual machine's interval timer at location X'50'.
virtual machine (VM): (1) A functional equivalent of a computing system. In VM/ESA, virtual machines can simulate the System/370, 370-XA, ESA/370, and ESA/390 functions. In addition, on ESA/390 systems, the XC virtual machine architecture is available. Each virtual machine is controlled by an operating system. VM controls the concurrent execution of several virtual machines on an actual processor complex. (2) See authorized virtual machine, AVS virtual machine, ESA virtual machine, expanded virtual machine assist, guest virtual machine (GVM), in-queue virtual machine, multiple-access virtual machine, pageable virtual machine, preferred virtual machine, service pool virtual machine, service virtual machine, sink virtual machine, source virtual machine, TSAF virtual machine, virtual machine (VM), virtual machine assist (VMA), virtual machine communication facility (VMCF), virtual machine control block (VMBLOK), virtual machine group, virtual machine operator, virtual machine operator's console, virtual machine reset, virtual=virtual machine (V=V machine), XA virtual machine, XC virtual machine, 370 virtual machine.
virtual machine assist (VMA): A hardware feature available on certain VM/ESA-supported System/370 models that causes a significant reduction in the real supervisor state time that VM/ESA uses to control the operation of virtual storage systems such as VSE, DOS/VS and OS/VS and, to a lesser extent, CMS, DOS, and OS when running under VM/ESA. VM/ESA supervisor state time is reduced because the VMA feature, instead of VM/ESA, intercepts and handles interruptions caused by SVCs, other than SVC 76, and certain privileged instructions. See CP assist, expanded virtual machine assist, Extended Control Program Support (ECPS:VM/370), and virtual interval timer assist.
virtual machine communication facility (VMCF): A CP function that provides a method of communication and data transfer between virtual machines operating under the same VM/ESA system.
virtual machine control block (VMBLOK): The primary control block for many activities related to a single virtual machine. This block contains, for each virtual machine, the following types of information: the dispatch and priority level of the virtual machine, the virtual machine's processor registers, preferred virtual machine options currently in effect, and information concerning all other significant activities.
virtual machine group: The concept in GCS of two or more virtual machines associated with each other through the same named system (for example, IPL GCS1). Virtual machines in a group share common read/write storage and can communicate with one another through facilities provided by GCS. Synonymous with group. See single user group.
virtual machine operator: Any user who loads and runs an operating system in a virtual machine. Contrast with real system operator.
virtual machine operator's console: The virtual machine operator's logon terminal, which simulates the hardware system console functions for the guest operating system. Messages destined for the hardware system console are presented to the virtual machine operator's console.
virtual machine reset: A collective term for the simulation of the system-reset-normal or system-reset-clear processes defined by the System/370 or System/390 hardware architectures. Among other things, virtual machine reset is an event that causes CP to recover many resources associated with a virtual machine, such as IUCV or APPC paths and data spaces. Virtual machine reset can result from issuing such CP commands as SYSTEM CLEAR, SYSTEM RESET, IPL or LOGOFF.
Virtual Machine Serviceability Enhancements Staged/Extended (VMSES/E): A component of VM/ESA that provides the tools for installing and servicing the various components of the VM product after VM/ESA Rel. 1.0. It is also the strategic installation and service tool for all of the other products that run on those VM/ESA platforms.
Virtual Machine/Enterprise Systems Architecture (VM/ESA): An IBM licensed program that manages the resources of a single computer so that multiple computing systems appear to exist. Each virtual machine is the functional equivalent of a real machine.
Virtual Machine/VTAM Communications Network Application (VM/VCNA): A program that runs in the VTAM service machine. VM/VCNA controls the physical appearance of the screen when displaying output on a VM/ESA terminal attached to an SNA network.
virtual print: (1) An agent that lets the user define and use a printer not connected to the PC being used. (2) The service that provides virtual print for the PC.
virtual printer: A printer simulated on disk by CP for a virtual machine. The virtual device type and I/O address are usually defined in the VM/ESA directory entry for that virtual machine.
virtual punch: A card punch simulated on disk by CP for a virtual machine. The virtual device type and I/O address are usually defined in the VM/ESA directory entry for that virtual machine.
virtual reserve/release: A function that lets many operating systems such as MVS, SVS, VS1, and VM/ESA itself all run as virtual machines under the same VM/ESA operating system and have data protection on a minidisk. It prevents many users of the same data file from simultaneously accessing the same data, particularly when that data is being updated.
virtual screen: A functional simulation of a physical screen. A virtual screen is a presentation space where data is maintained. The user can view pieces of the virtual screen through a window on the physical screen.
virtual spooling device: Unit record devices simulated on disk by CP. The virtual device type and I/O addresses are defined in the VM/ESA directory or else by the CP DEFINE command. CP's spooling facilities let multiple virtual machines share the real unit record devices. In addition, VM/ESA has extended the concept of spooling to include the logging of all I/O to and from the virtual machine system console. See virtual card reader, virtual console spooling, and virtual printer (or punch).
virtual storage: Storage space that can be regarded as addressable main storage by the user of a computer system in which virtual addresses are mapped into real addresses. The size of virtual storage is limited by the addressing scheme of the computing system and by the amount of auxiliary storage available, not by the actual number of main storage locations.
virtual storage access method (VSAM): An access method for direct or sequential processing of fixed and variable-length records on direct access devices. The records in a VSAM data set or file can be organized in logical sequence by a key field (key sequence), in the physical sequence in which they are written on the data set or file (entry-sequence), or by relative-record number.
virtual storage extended (VSE): The generalized term that indicates the combination of the DOS/VSE system control program and the VSE/Advanced Functions licensed program. Note that in certain cases, the term DOS is still used as a generic term; for example, disk packs initialized for use with VSE or any predecessor DOS or DOS/VS system are sometimes called DOS disks. Also note that the DOS-like simulation environment provided under the VM/ESA CMS component and CMS/DOS exists on VM/ESA licensed programs and continues to be called CMS/DOS.
virtual storage extended/priority output writers, execution processors, and input readers (VSE/POWER): An IBM licensed program that primarily spools input and output. The networking functions of the program enable a VSE/SP system to exchange files with or run jobs on another remote processor.
virtual supervisor state: A condition, controlled by a virtual machine's current PSW, during which the control program lets the virtual machine issue I/O and other privileged instructions. When these instructions are not emulated, the control program intercepts these instructions and simulates their functions for the virtual machine.
Virtual Telecommunications Access Method (VTAM): An IBM licensed program that controls communication and the flow of data in a computer network. It provides single-domain, multiple-domain, and multiple-network capability. VTAM runs under MVS, OS/VS1, VM/ESA, and VSE.
virtual wait time: The period during which the control program suspends the processing of a program while a required resource is unavailable.
virtual=fixed machine (V=F machine): A preferred virtual machine with a fixed, contiguous area of host real storage that does not start at page 0. CP provides performance enhancements for this virtual machine. See also multiple preferred guests, preferred virtual machine, virtual=real machine.
virtual=real area (V=R area): The part of real storage, starting with real page 1, where a virtual=real machine can execute. CP maintains control of real page zero; only page zero of the virtual=real machine is relocated. Only one virtual machine at a time can occupy the virtual=real area. The area must be defined to contain the largest virtual=real machine likely to run.
virtual=real machine (V=R machine): A preferred virtual machine with a fixed, contiguous area of host real storage that starts at page 0. CP provides performance enhancements and an automatic recovery facility for this virtual machine. See also multiple preferred guests, preferred virtual machine, virtual=real area, virtual=real machine recovery, and virtual=virtual machine.
virtual=real machine recovery (V=R machine recovery): A CP function that lets the V=R machine resume operation after most CP abnormal terminations. When possible, the facility reestablishes the V=R machine environment, allowing the operating system running in that virtual machine to perform its own recovery processes. See automatic software re-IPL.
virtual=real option: A VM/ESA performance option that lets a virtual machine run in VM/ESA's virtual=real area. This option eliminates CP paging and optionally, CCW translation for this virtual machine. Synonymous with V=R.
virtual=virtual machine (V=V machine): A virtual machine that runs in the dynamic paging area. CP pages this virtual machine's guest real storage in and out of host real storage. See dynamic paging area, virtual=fixed machine, and virtual=real machine.
VM: Virtual machine.
VM Data Spaces: A facility of VM/ESA that is provided when VM/ESA is running on an ESA/390 processor. Using ESA/390 interpretive execution (SIE) enhancements, the VM Data Spaces facility provides the ESA/XC virtual machine architecture and allows virtual machines to create and access multiple host-managed address spaces. See ESA/XC architecture.
VM directory: A CP disk file that defines each virtual machine's typical configuration: the user ID, password, regular and maximum allowable virtual storage, CP command privilege class or classes allowed, dispatching priority, logical editing symbols to be used, account number, and CP options desired. Synonymous with CP directory.
VM domain controller: Part of the ISFC function of CP that lets user programs connect to and communicate with resources on different VM systems or domain controller workstations in a CS collection.
VM hardware assist: A general term that represents any or all of the following hardware assist functions: expanded virtual machine assist, ECPS, virtual interval timer assist, and VMA.
VM part catalog table: A table that identifies the product or component that owns all files residing on a disk and the VMSES/E command that last modified or created the file. It is modified each time VMSES/E modifies or creates a file on a disk identified in the :MDA section of the product parameter file.
VM Personal Workstation Communication Facility PRPQ P81056 (VM PWSCF): An IBM programming RPQ that handles communications between VM/ESA Release 1.0 (370 Feature) and VM/SP Release 6 systems and programmable workstations that run VM PWSCS. VM PWSCF lets APPC paths span systems, allowing transaction programs running on these systems to communicate.
VM Programmable Workstation Communication Services (VM PWSCS): An IBM program product that runs on LAN-based workstations. VM PWSCS provides program-to-program CPI Communications between programmable workstations and VM systems.
VM PWSCF: VM Personal Workstation Communication Facility Programming RPQ P81056.
VM READ screen status: For a display terminal used as a virtual console under VM/ESA, an indicator located in the lower right of the screen that displays when the user's virtual machine is not executing, but is waiting for a response or a request for work from the user.
VM/ESA: Virtual Machine/Enterprise Systems Architecture.
VM/ESA domain controller: Part of the ISFC function of CP that lets user programs connect to and communicate with resources on different VM/ESA, OS/2 Extended Edition, or AIX PS/2 systems in a CS collection. See OS/2 domain controller and AIX PS/2 domain controller.
VM/Pass-Through Facility: A facility that lets VM users interactively access remote system and processor nodes. These can be remote IBM 4300 processors, other VM systems, with or without this facility installed, or System/370- compatible non-VM systems.
VM/VCNA: Virtual Machine/VTAM Communications Network Application.
VM/VS handshaking feature: A communication interface between VM/ESA and other operating systems running a virtual machine under VM/ESA. These operating systems and CP make each other aware of mutual capabilities and requirements.
VM/370 hardware assist: This refers to both the virtual machine assist function and the VM/370 ECPS. Some form of the VM/370 hardware assist is available on all VM/370 supported System/370 systems except the 155-II, 165-III, and 4341-2.
VMA: Virtual machine assist.
VMBLOK: Virtual machine control block.
VMCF: Virtual machine communication facility.
VMLIB: The name of the CSL supplied with VM/ESA and that contains routines to do various VM functions.
VMSES/E: (1) Virtual Machine Serviceability Enhancements Staged/Extended. (2) See VMSES/E installation/service tool.
VMSES/E installation/service tool: Two VMSES/E user interfaces, VMFINS and VMFSIM, all of the VMSES/E commands, and the service-level and system-level software inventories. Usually referred to as VMSES/E.
volid: Volume identifier.
volume identifier (volid): The volume identification label for a disk.
volume table of contents (VTOC): (1) A table on a direct access volume that describes each data set on the volume. (2) An area on a disk or diskette that describes the location, size, and other characteristics of each file and library on the disk or diskette.
VSAM: Virtual storage access method.
vscreen: Virtual screen.
VSCS: VTAM SNA Console Support.
VSE: Virtual storage extended.
VSE/POWER: Virtual Storage Extended/Priority Output Writers, Execution Processors, and Input Readers.
VSM: VTAM service machine.
VTAM: Virtual Telecommunications Access Method.
VTAM service machine (VSM): A virtual machine that contains an operating system (OS/VS1 or DOS/VSE), an access method (ACF/VTAM or ACF/VTAME), and VM/VCNA. VSM forms the interface for SNA communication in VM/ESA.
VTOC: Volume table of contents.

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+---+ W +---+

WAN: Wide area network.
warm start: (1) The result of an IPL that does not erase previous system data. (2) The automatic reinitialization of the VM/ESA control program that occurs if the control program cannot continue processing. Closed spool files and the VM/ESA accounting information are not lost. Contrast with checkpoint (CKPT) start, cold start, and force start.
wide area network (WAN): A network that provides communication services to a geographic area larger than that served by an LAN. Contrast with local area network (LAN).
wild-card character: A symbol used in a command to represent one or more characters. In VM/ESA, the wild-card characters are the asterisk (*) and the percent symbol (%).
window: An area on the physical screen where virtual screen data can be displayed. Windowing lets the user do such functions as defining, positioning, and overlaying windows; scrolling backward and forward through data; and writing data into virtual screens.
windowing: A set of functions that lets the user view and manipulate data in user-defined areas of the physical screen called windows. Windowing support lets the user define, position, and overlay windows; scroll backward and forward through data; and write data into virtual screens.
work unit: In CMS, a group of related operations that can be either committed or rolled back as a unit. When the operations associated with a work unit are committed or rolled back, new operations can be associated with the same work unit. These operations can also be committed or rolled back. (The work unit is, in a sense, reusable.) Multiple work units may be active. See active work unit, inactive work unit, and logical unit of work.
work unit ID: A nonnegative integer value, unique within a virtual machine, that identifies a work unit.
working set: The estimated number of pages of real storage that the virtual machine needs to execute.
workstation: An I/O device from which jobs can be submitted to a host system for processing, or to which output can be returned, or both.
wrap spool file: A wrap spool file is established when the CPTRAP invoker issues CPTRAP START with the WRAP option. The size of the wrap spool file is determined by the file size information provided with the CPTRAP START WRAP nnnnn command. (nnnnn is the number of 4K blocks of records.) Records will be added to the spool file until the specified SPOOL size limit is reached. Then, newer records replace older records in the spool file thereby using the same spool area over again.
write authority: The authority to read or change the contents of a file or directory. Write authority implies read authority.
write-only rule: A requirement that the security label of the object dominate that of the subject. This prevents a subject from writing down. See also read-only rule and read/write rules.
writing down: An event in which a subject with a given security label writes in an object whose security label it does not dominate. A B1 trusted computing base does not allow writing down. Contrast reading up. See also domination rule.

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+---+ X +---+

XA mode: A GCS mode of operation on ESA that uses the full capabilities of the Extended Systems Architecture.
XA virtual machine: A virtual machine that simulates System/370-Extended Architecture functions. Contrast with 370 virtual machine, ESA virtual machine, and XC virtual machine.
XC virtual machine: A virtual machine operating mode in which the virtual machine is simulating ESA/XC architecture. XC virtual machines can be provided only when VM/ESA is running on an ESA/390 processor. Contrast with 370 virtual machine, ESA virtual machine, and XA virtual machine.
XEDIT: The CMS facility, containing the XEDIT command and XEDIT subcommands and macros, that lets a user create, change, and manipulate CMS files.
XEDIT macro: (1) A procedure defined by a frequently used command sequence to do a commonly required editing function. A user creates the macro to save repetitious reentering of the sequence, and invokes the entire procedure by entering a command (that is, the macro file's file name). The procedure can consist of a long sequence of XEDIT commands and subcommands or both, and CMS and CP commands or both, along with REXX or EXEC 2 control statements to control processing within the procedure. (2) A CMS file with a file type of XEDIT.
XEDIT profile macro: A special XEDIT macro with a file name of PROFILE and a file type of XEDIT that a user can create. It is automatically executed when an XEDIT command (or subcommand) is entered.
XMEM: This option enables MVS cross memory services for the MVS/SP virtual machine. When specified, the MVS/SP V=R user can use the System/370 extended facility enhancements and cross memory services implemented in Release 3 and all subsequent releases of MVS/SP. The IBM 3033 processors equipped with the 3033 extensions feature and the 3081 processor complex support cross memory services (XMEM). Cross memory is initiated when it is present on either or both processors of an AP or MP system. The MVS/SP guest virtual machine thus operates in supervisor state with direct control of its own I/O operations under VM/ESA.

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+---+ Y +---+

Y-STAT: A block of storage that contains the FSTs associated with file mode Y. The FSTs are sorted so that a binary search can search for files. The Y-STAT usually resides in the CMS nucleus so it can be shared. Only files with file mode of 2 will have their associated FSTs in the Y-STAT.

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+---+ Z +---+

zap: To modify or dump an individual text file, using the ZAP command or the ZAPTEXT EXEC.
zone setting: In the CMS editor, a number range that specifies the positions within each data line that can be scanned and edited. In the XEDIT editor, the starting position and ending position (columns) of each record within which the editor searches for targets.

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+---+ Numerics +---+

2305: Refers to the IBM 2305 Fixed Head Storage Device, Models 1 and 2.
270X: Refers to the IBM 2701, 2702, and 2703 Transmission Control Units or the Integrated Communications Adapter (ICA) on the System/370 Model 135.
2741: Refers to the IBM 2741 Terminal. Information on the 2741 also applies to the IBM 3767 Terminal, unless otherwise noted.
3033: Refers to the IBM 3033 Processor.
3081: Refers to the IBM 3081 Processor Unit Model D16.
3088: Refers to the IBM 3088 Multisystem Channel Communications Unit, Models 1 and 2.
3262: Refers to the IBM 3262 Printer, Models 1 and 11.
3270: Refers to a series of IBM display devices, for example, the IBM 3275, 3276 Controller Display Station; 3277, 3278, and 3279 Display Stations; the 3290 Information Panel; and the 3287 and 3286 printers. A specific device type is used only when a distinction is required between device types. Information about display terminal usage also refers to the IBM 3138, 3148, and 3158 Display Consoles when used in display mode, unless otherwise noted.
3284: Refers to the IBM 3284 Printer. Information on the 3284 also pertains to the IBM 3286, 3287, 3288, and 3289 printers, unless otherwise noted.
3289: Refers to the IBM 3289 Model 4 Printer.
3310: Refers to the IBM 3310 Direct Access Storage Device.
3330: Refers to the IBM 3330 Disk Storage Device.
3340: Refers to the IBM 3340 Direct Access Storage Device.
3350: Refers to the IBM 3350 Direct Access Storage Device when used in native mode.
3370: Refers to the IBM 3370 Direct Access Storage Device.
3375: Refers to the IBM 3375 Direct Access Storage Device.
3380: Refers to the IBM 3380 Direct Access Storage Device.
3390: Refers to the IBM 3390 Direct Access Storage Device.
3422: Refers to the IBM 3422 Magnetic Tape Subsystem.
3480: Refers to the IBM 3480 Magnetic Tape Subsystem.
3490: Refers to the IBM 3490 Magnetic Tape Subsystem.
370 mode: A GCS mode of operation on ESA that simulates 370 architecture.
370 virtual machine: A virtual machine that simulates System/370 functions. Contrast with XA virtual machine, ESA virtual machine, and XC virtual machine.
370x: Refers to the IBM 3704/3705 Communication Controllers.
3725: Refers to the IBM 3725 Communication Controllers.
3800: Refers to the IBM 3800 Printing Subsystems. A specific device type is used only when a distinction is required between device types.
3850: Refers to the IBM 3850 Mass Storage System.
3880: Refers to the IBM 3880 Storage Control Units.
3990: Refers to the IBM 3990 DASD storage control units.
4245: Refers to the IBM 4245 Printer.
4248: Refers to the IBM 4248 Printer.
4250: Refers to the IBM 4250 Printer.
6262: Refers to the IBM 6262 Printer.
9032: Refers to the IBM ES/9000 Enterprise Systems Connection (ESCON) Director, Model 2.
9033: Refers to the IBM ES/9000 Enterprise Systems Connection (ESCON) Director, Model 1.
9313: Refers to the IBM 9313 Direct Access Storage Device.
9332: Refers to the IBM 9332 Direct Access Storage Device, Model 400.
9335: Refers to the IBM 9335 Direct Access Storage Device, Models A01 and B01.
9347: Refers to the IBM 9347 Tape Drive.
9370: Refers to a series of processors, namely the IBM 9371 Models 10, 12, and 14, the IBM 9373 Model 20, the IBM 9375 Models 40 and 60, the IBM 9377 Model 90, and other models.

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2000-4-7 document@uic.edu