Glossary

This glossary defines technical terms and abbreviations used in DFSMS documentation. If you do not find the term you are looking for, refer to the index of the appropriate DFSMS manual or view the Glossary of Computing Terms located at:

http://www.ibm.com/ibm/terminology/

This glossary includes terms and 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 part 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.
The IBM Dictionary of Computing, New York: McGraw-Hill, 1994.

The following cross-reference is used in this glossary:

See:: This refers the reader to (a) a related term, (b) a term that is the expanded form of an abbreviation or acronym, or (c) a synonym or more preferred term.

A
access method services: A multifunction service program that to manages both VSAM and non-VSAM data sets and integrated catalog facility catalogs or VSAM catalogs. It defines data sets and allocates space for VSAM data sets, VSAM catalogues, and ICF catalogs. It converts indexed-sequential (ISAM) data sets to key-sequenced data sets, modifies data set attributes in the catalog, reorganizes data sets, facilitates data portability among operating systems, creates backup copies of data sets and indexes, helps make inaccessible data sets accessible, lists the records of data sets and catalogs, defines and builds alternate indexes, and converts CVOLs and VSAM catalogs to integrated catalog facility catalogs.
access permission: A group of designations that determine who can access a particular AIX or UNIX file and how the user can access the file.
ACS: Automatic class selection.
active control data set (ACDS): A VSAM linear data set that contains an SCDS that has been activated to control the storage management policy for the installation. When activating an SCDS, you determine which ACDS will hold the active configuration (if you have defined more than one ACDS). The ACDS is shared by each system that is using the same SMS configuration to manage storage. See also source control data set, communications data set.
alias: An alternative name for an ICF user catalog, a non-VSAM file, or a member of a partitioned data set (PDS) or PDSE.
automatic class selection (ACS): A mechanism for assigning Storage Management Subsystem classes and storage groups to data sets.
B
base addressing space: On an extended address volume, the cylinders with addresses below 65 536. These cylinder addresses are represented by 16-bit cylinder numbers or by 28-bit cylinder numbers with the high-order 12 bits equal to zero.
basic format: The format of a data set that has a data set name type (DSNTYPE) of BASIC. A basic format data set is a sequential data set that is specified to be neither large format nor extended format. The size of a basic format data set cannot exceed 65 535 tracks on each volume.
basic partition access method (BPAM): An access method that can be applied to create program libraries in direct access storage for convenient storage and retrieval of programs.
BPAM: See Basic partitioned access method.
C
catalog: A directory of files and libraries, with reference to their locations. A catalog may contain other information such as the types of devices in which the files are stored, passwords, blocking factors.; A data set that contains extensive information required to locate other data sets, to allocate and deallocate storage space, to verify the access authority of a program or operator, and to accumulate data set usage statistics. (A) (ISO); To enter information about a file or a library into a catalog. (A) (ISO); The collection of all data set indexes that are used by the control program to locate a volume containing a specific data set.; To include the volume identification of a data set in the catalog.; See VSAM master catalog, VSAM user catalog.
CAS: catalog address space.
catalog address space: The area of virtual storage where catalog functions are performed. It contains tables with all user catalog names identified in the master catalog, their aliases, and their associated volume serial numbers. Any changes to the master catalog are automatically reflected in these tables.
coupling facility (CF): The hardware that provides high-speed caching, list processing, and locking functions in a Parallel Sysplex.
cylinder-managed space: The space on the volume that is managed only in multicylinder units. Cylinder-managed space begins at cylinder address 65 520. Each data set occupies an integral number of multicylinder units. Space requests targeted for the cylinder-managed space are rounded up to the size of a multicylinder unit. The cylinder-managed space exists only on extended address volumes.
D
DASD volume: A DASD space identified by a common label and accessed by a set of related addresses. See also volume, primary storage, migration level 1, migration level 2.
data class: A collection of allocation and space attributes, defined by the storage administrator, that are used to create a data set.
device: This term is used interchangeably with unit. For a disk or tape, a unit on which a volume may be mounted. For example, a tape drive is a device; a tape cartridge is a volume. Device also applies to other types of equipment, such as a card reader or a channel-to-channel (CTC) adapter.
Device Support Facilities (ICKDSF): A program used for initialization of DASD volumes and track recovery.
DFSMS: See Data Facility Storage Management Subsystem.
DFSMSdfp: A DFSMS functional component or base element of z/OS, that provides functions for storage management, data management, program management, device management, and distributed data access.
DFSMSdss: A DFSMS functional component or base element of z/OS, used to copy, move, dump, and restore data sets and volumes.
DFSMShsm: A DFSMS functional component or base element of z/OS, used for backing up and recovering data, and managing space on volumes in the storage hierarchy.
DFSMS environment: An environment that helps automate and centralize the management of storage. This is achieved through a combination of hardware, software, and policies. In the DFSMS environment for MVS, this function is provided by DFSMS, DFSORT, and RACF. See also system-managed storage.
direct access device space management (DADSM): A collection of subroutines that manages space on disk volumes. The subroutines are: Create, Scratch, Extend, and Partial Release.
dump: A capture of valuable storage information at the time of an error.
E
ECS: Enhanced Catalog Sharing.
extended address volume (EAV): A volume with more than 65 520 cylinders.
extended addressing space (EAS): On an extended address volume, the cylinders with addresses that are equal to or greater than 65 536. These cylinder addresses require more than 16 bits to represent.
extended format: The format of a data set that has a data set name type (DSNTYPE) of EXTREQ or EXTPREF. The data set is structured logically the same as a data set that is not in extended format, but the physical format is different. A data set in extended format can be sequential or any type of VSAM data set. An extended format data set can optionally be striped or in compressed format or both. See also striped data set, compressed format.
extent: A file extent is a storage area for records allocated to a file by the server. Extents are not formally architected in DDM.
G
GDG: See generation data group.
GDS: See generation data set.
generation data group (GDG): A collection of historically related non-VSAM data sets that are arranged in chronological order; each data set is a generation data set.
generation data set: One generation of a generation data group.
I
ICKDSF: See Device Support Facilities program.
initial program load (IPL): The initialization procedure that causes an operating system to commence operation.; The process by which a configuration image is loaded into storage at the beginning of a work day or after a system malfunction.; The process of leading system programs and preparing a system to run jobs.; Synonymous with system restart, system startup.
Interactive Storage Management Facility (ISMF): The interactive interface of DFSMS/MVS that allows users and storage administrators access to the storage management functions.
Interactive System Productivity Facility (ISPF): An interactive base for ISMF.
IPL: See initial program load.
ISMF: See Interactive Storage Management Facility .
ISPF: See Interactive System Productivity Facility.
J
JCL: See Job control language.
Job control language (JCL): A problem-oriented language used to identify the job or describe its requirements to an operating system.
L
large format: The format of a data set that has a data set name type (DSNTYPE) of LARGE. A large format data set has the same characteristics as a sequential (non-extended format) data set, but its size on each volume can exceed 65 535 tracks. There is no minimum size requirement for a large format data set.
Logical partition (LPAR): An LPAR uses software and firmware to logically partition the resources on a system. An LPAR consists of processors, memory, and I/O slots available in one processor complex.
M
master catalog: A key-sequenced data set or file with an index containing extensive data set and volume information that VSAM requires to locate data sets or files, to allocate and deallocate storage space, to verify the authorization of a program or operator to gain access to a data set or file, and to accumulate usage statistics for data sets or files.
multicylinder unit: A fixed unit of disk space that is larger than a cylinder. For example, a multicylinder unit might be 21 cylinders; in this case, the number of the first cylinder in each multicylinder unit would be a multiple of 21.
multilevel security: A security policy that allows the classification of data and users based on a system of hierarchical security levels (for example: unclassified, secret, top secret) combined with a system of non-hierarchical security categories (for example: Project A, Project B, Project C). In order to access data, a user must have a security level greater than or equal to that of the data, and be authorized to all of the categories assigned to the data.
N
name hiding: Prevents unauthorized users from obtaining names about data sets.
nonVSAM data set: A data set allocated and accessed using one of the following methods: BDAM, BPAM, BISAM, BSAM, QSAM, QISAM.
P
partitioned data set (PDS): A data set on direct access storage that is divided into partitions, called members, each of which can contain a program, part of a program, or data.
partitioned data set extended (PDSE): A system-managed data set that contains an indexed directory and members that are similar to the directory and members of partitioned data sets. A PDSE can be used instead of a partitioned data set.
PDS: See Partitioned data set.
PDSE: See partitioned data set extended.
performance: A measurement of the amount of work a product can produce with a given amount of resources.; In a system-managed storage environment, a measurement of effective data processing speed with respect to objectives set by the storage administrator. Performance is largely determined by throughput, response time, and system availability.
pool storage group: A type of storage group that contains system-managed DASD volumes. Pool storage groups allow groups of volumes to be managed as a single entity. See also storage group.
R
RACF: See Resource access control facility.
Resource Access Control Facility (RACF): An IBM licensed program that is included in z/OS Security Server and is also available as a separate program for the z/OS and VM environments. RACF provides access control by identifying and verifying the users to the system, authorizing access to protected resources, logging detected unauthorized attempts to enter the system, and logging detected accesses to protected resources.
S
SCDS: See Source control data set.
sequential data set: A data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape. Contrast with direct data set.
SMS: Storage Management Subsystem.
SMS class: A list of attributes that SMS applies to data sets having similar allocation (data class), performance (storage class), or backup and retention (management class) needs.
SMS-managed data set: A data set that has been assigned a storage class.
source control data set (SCDS): A VSAM linear data set containing an SMS configuration. The SMS configuration in an SCDS can be changed and validated using ISMF. See also active control data set, communications data set.
storage administrator: A person in the data processing center who is responsible for defining, implementing, and maintaining storage management policies.
storage class: A collection of storage attributes that identify performance goals and availability requirements, defined by the storage administrator, used to select a device that can meet those goals and requirements.
storage facility: The physical components that comprise a single storage server (DS8000 or DS6000) including the base frame and the optional expansion frames. A storage facility is composed of two processor complexes (servers) and some number of storage devices that are packaged in one or more enclosures with associated power supplies and cooling.
storage facility image: For hosts that use FICON/ESCON I/O commands, a storage facility image contains one or more ESCON or Fibre Channel (FICON) I/O interfaces (ports) that can access one or more control-unit images. Each control-unit image has an associated set of devices. Each device is assigned a unique device address on the control-unit image. Depending upon the model, more than one storage facility image can be configured on a storage facility. (For DS8000, the storage facility can support more than one storage facility image.) A storage facility image might also be referred to as a storage image.
storage group: A collection of storage volumes and attributes, defined by the storage administrator. The collections can be a group of DASD volumes or tape volumes, or a group of DASD, optical, or tape volumes treated as a single object storage hierarchy. See also VIO storage group, pool storage group, tape storage group, object storage group, object backup storage group, dummy storage group.
storage management: The activities of data set allocation, placement, monitoring, migration, backup, recall, recovery, and deletion. These can be done either manually or by using automated processes. The Storage Management Subsystem automates these processes for you, while optimizing storage resources. See also Storage Management Subsystem.
Storage Management Subsystem (SMS): A DFSMS facility used to automate and centralize the management of storage. Using SMS, a storage administrator describes data allocation characteristics, performance and availability goals, backup and retention requirements, and storage requirements to the system through data class, storage class, management class, storage group, and ACS routine definitions.
stripe: In DFSMS, the portion of a striped data set, such as an extended format data set, that resides on one volume. The records in that portion are not always logically consecutive. The system distributes records among the stripes such that the volumes can be read from or written to simultaneously to gain better performance. Whether it is striped is not apparent to the application program.
sysplex: A set of z/OS systems communicating and cooperating with each other through certain multisystem hardware components and software services to process customer workloads.
system-managed storage: Storage managed by the Storage Management Subsystem. SMS attempts to deliver required services for availability, performance, and space to applications. See also system-managed storage environment.
system programmer: A programmer who plans, generates, maintains, extends, and controls the use of an operating system and applications with the aim of improving overall productivity of an installation.
T
threshold: A storage group attribute that controls the space usage on DASD volumes, as a percentage of occupied tracks versus total tracks. The low migration threshold is used during primary space management and interval migration to determine when to stop processing data. The high allocation threshold is used to determine candidate volumes for new data set allocations. Volumes with occupancy lower than the high threshold are selected over volumes that meet or exceed the high threshold value.
track address: A 32-bit number that identifies each track within a volume. A track address is in the format hex CCCCcccH, where CCCC is the low-order 16 bits of the cylinder number, ccc is the high-order 12 bits of the cylinder number, and H is the four-bit track number. For compatibility with older programs, the ccc portion is hex 000 for tracks in the base addressing space.
track-managed space: The space on a volume that is managed in tracks and cylinders. For an extended address volume, track-managed space ends at cylinder address 65 519. Each data set occupies an integral number of tracks.
U
UNIX: A highly portable operating system originally developed by Bell Laboratories that features multiprogramming in a multi-user environment. UNIX is implemented in the C language. UNIX was originally developed for use on minicomputers but has been adapted on mainframes and microcomputers. It is especially suitable for multiprocessor, graphics, and vector-processing systems.
V
VLF: Virtual lookaside facility
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 the relative-record number.
volume: The storage space on DASD, tape, or optical devices, which is identified by a volume label. See also DASD volume, optical volume, tape volume.
VSAM: See virtual storage access method.
Z
z/OS: z/OS is a network computing-ready, integrated operating system consisting of more than 50 base elements and integrated optional features delivered as a configured, tested system.
z/OS Network File System: A base element of z/OS, that allows remote access to z/OS host processor data from workstations, personal computers, or any other system on a TCP/IP network that is using client software for the Network File System protocol.