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.

ACS

See automatic class selection

active data

For tape mount management, application data that is frequently referenced, usually small in size, and managed better in the DFSMS storage hierarchy than on tape. Contrast with inactive data.

allocation

Generically, the entire process of obtaining a volume and unit of external storage, and setting aside space on that storage for a data set.

automatic class selection (ACS)

A mechanism for assigning SMS classes and storage groups to data sets.

automated tape library data server

A device consisting of robotic components, cartridge storage areas, tape subsystems, and controlling hardware and software, together with the set of tape volumes that reside in the library and can be mounted on the library tape drives. Contrast with manual tape library. See also tape library.

automatic class selection (ACS) routine

A procedural set of ACS language statements. Based on a set of input variables, the ACS language statements generate the name of a predefined SMS class, or a list of names of predefined storage groups, for a data set.

automatic dump

In DFSMShsm, the process of using DFSMSdss automatically to do a full-volume dump of all allocated space on a primary storage volume to designated tape dump volumes.

availability

For a storage subsystem, the degree to which a data set or object can be accessed when requested by a user.

backup

The process of creating a copy of a data set or object to be used in case of accidental loss.

base configuration

The part of an SMS configuration that contains general storage management attributes, such as the default management class, default unit, and default device geometry. It also identifies the systems or system groups that an SMS configuration manages.

Cartridge System Tape

The base tape cartridge media used with 3480 or 3490 Magnetic Tape Subsystems. Contrast with Enhanced Capacity Cartridge System Tape.

class transition

An event that brings about change to an object’s service-level criteria, causing OAM to invoke ACS routines to assign a new storage class or management class to the object.

construct

One of the following: data class, storage class, management class, storage group, aggregate group, base configuration.

DASD

see direct access storage device

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.

Data Facility Sort

An IBM licensed program that is a high-speed data processing utility. DFSORT provides an efficient and flexible way to handle sorting, merging, and copying operations, as well as providing versatile data manipulation at the record, field, and bit level.

data set

In DFSMS, the major unit of data storage and retrieval, consisting of a collection of data in one of several prescribed arrangements and described by control information to which the system has access. In z/OS non-UNIX environments, the terms data set and file are generally equivalent and sometimes are used interchangeably. See also file. In z/OS UNIX environments, the terms data set and file have quite distinct meanings.

default unit

Part of the SMS base configuration, it identifies an esoteric (such as SYSDA) or generic (such as 3390) device name. If a user omits the UNIT parameter on the JCL or the dynamic allocation equivalent, SMS applies the default unit if the data set has a disposition of MOD or NEW and is not system-managed.

Device Support Facilities (ICKDSF)

A program used for initialization of DASD volumes and track recovery.

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.

DFSMShsm-managed volume

A primary storage volume, which is defined to DFSMShsm but which does not belong to a storage group.

A volume in a storage group, which is using DFSMShsm automatic dump, migration, or backup services. Contrast with system-managed volume, DFSMSrmm-managed volume.

DFSMSrmm

A DFSMS functional component or base element of z/OS, that manages removable media.

DFSMSrmm-managed volume

A tape volume that is defined to DFSMSrmm. Contrast with system-managed volume, DFSMShsm-managed volume.

DFSORT

see Data Facility Sort

direct access storage device (DASD)

A mass storage medium on which a computer stores data.

dummy storage group

A type of storage group that contains the serial numbers of volumes no longer connected to a system. Dummy storage groups allow existing JCL to function without having to be changed. See also storage group.

Enhanced Capacity Cartridge System Tape

Cartridge system tape with increased capacity that can only be used with 3490E Magnetic Tape Subsystems. Contrast with Cartridge System Tape.

erase-on-scratch

The physical erasure of data on a DASD data set when the data set is deleted (scratched).

expiration

The process by which data sets or objects are identified for deletion because their expiration date or retention period has passed. On DASD, data sets and objects are deleted. On tape, when all data sets have reached their expiration date, the tape volume is available for reuse.

In DFSMSrmm, all volumes have an expiration date or retention period set for them either by vital record specification policy, by user-specified JCL when writing a data set to the volume, or by an installation default. When a volume reaches its expiration date or retention period, it becomes eligible for release.

file

A collection of information treated as a unit. In z/OS non-UNIX environments, the terms data set and file are generally equivalent and are sometimes used interchangeably. See also data set.

filtering

The process of selecting data sets based on specified criteria. These criteria consist of fully or partially-qualified data set names or of certain data set characteristics.

GB

See gigabyte

GDG

See generation data group

GDS

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 called a generation data set.

gigabyte (GB)

One billion (10⁹) bytes.

group

With respect to partitioned data sets, a member and the member's aliases that exist in a PDS or PDSE, or in an unloaded PDSE.

A collection of users who can share access authorities for protected resources.

ICKDSF

see Device Support Facilities

ICL

Integrated cartridge loader

IDCAMS

Access method services

IDRC

see improved data recording capability

improved data recording capability (IDRC)

A recording mode that can increase the effective cartridge data capacity and the effective data rate when enabled and used. IDRC is always enabled on the 3490E Magnetic Tape Subsystems.

inactive data

A copy of active data, such as vital records or a backup copy of a data set. Inactive data is never changed, but can be deleted or superseded by another copy.

In tape mount management, data that is written once and never used again. The majority of this data is point-in-time backups.

Objects infrequently accessed by users and eligible to be moved to the optical library or shelf.

Contrast with active data.

interval migration

In DFSMShsm, automatic migration that occurs when a threshold level of occupancy is reached or exceeded on a DFSMShsm-managed volume, during a specified time interval. Data sets are moved from the volume, largest eligible data set first, until the low threshold of occupancy is reached.

JCL

see job control language

job control language (JCL)

A control language used to identify a job to an operating system and to describe the job's requirements.

KSDS

see key-sequenced data set

key-sequenced data set (KSDS)

A VSAM data set whose records are loaded in key sequence and controlled by an index.

management class

A collection of management attributes, defined by the storage administrator, used to control the release of allocated but unused space; to control the retention, migration, and backup of data sets; to control the retention and backup of aggregate groups, and to control the retention, backup, and class transition of objects.

MB

see megabyte

megabyte (MB)

1) For processor storage, real and virtual storage, and channel volume, 2²⁰ or 1 048 576 bytes. 2) For disk storage capacity and communications volume, 1 000 000 bytes.

migration

The process of moving unused data to lower cost storage in order to make space for high-availability data. If you wish to use the data set, it must be recalled. See also migration level 1, migration level 2.

migration control data set (MCDS)

In DFSMShsm, a VSAM key-sequenced data set that contains statistics records, control records, user records, records for data sets that have migrated, and records for volumes under migration control of DFSMShsm.

migration level 1

DFSMShsm-owned DASD volumes that contain data sets migrated from primary storage volumes. The data can be compressed. See also storage hierarchy. Contrast with primary storage, migration level 2.

migration level 2

DFSMShsm-owned tape or DASD volumes that contain data sets migrated from primary storage volumes or from migration level 1 volumes. The data can be compressed. See also storage hierarchy. Contrast with primary storage, migration level 1.

modeling

The process of projecting future storage requirements for DASD and tape if data is managed by DFSMS.

Multiple Virtual Storage (MVS)

The short name for the MVS element of the z/OS operating system.

MVS

See Multiple Virtual Storage

OAM

See object access method

object access method (OAM)

An access method that provides storage, retrieval, and storage hierarchy management for objects and provides storage and retrieval management for tape volumes contained in system-managed libraries.

object backup storage group

A type of storage group that contains optical or tape volumes used for backup copies of objects. See also storage group.

object storage group

A type of storage group that contains objects on DASD, tape, or optical volumes. See also storage group.

optical volume

Storage space on an optical disk, identified by a volume label. See also volume.

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 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

(1) A measurement of the amount of work a product can produce with a given amount of resources. (2) In a DFSMS 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.

permanent data set

A user-named data set that is normally retained for longer than the duration of a job or interactive session. Contrast with temporary data set.

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.

primary storage

A DASD volume available to users for data allocation. The volumes in primary storage are called primary volumes. See also storage hierarchy. Contrast with migration level 1, migration level 2.

program management

The task of preparing programs for execution, storing the programs, load modules, or program objects in program libraries, and executing them on the operating system.

RACF

See Resource Access Control Facility

recall mount

A mount that results from a data set being referenced after it has migrated to migration level 1 DASD or migration level 2 tape. There are two types of recall mounts: level 2 to primary DASD, which requires a mount, and level 1 DASD to primary DASD, which only requires data transfer and thus is less costly.

Resource Access Control Facility (RACF)

An IBM-licensed program or informal name for a base element of z/OS, that provides for access control by identifying and verifying the users to the system, authorizing access to protected resources, logging the detected unauthorized attempts to enter the system, and logging the detected accesses to protected resources. The formal name for RACF in z/OS is z/OS Security Server.

recovery

The process of rebuilding data after it has been damaged or destroyed, often by using a backup copy of the data or by reapplying transactions recorded in a log.

SFF

Single file format

SMF

See system management facilities

SMS

See Storage Management Subsystem

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 control

The component in a storage subsystem that handles interaction between processor channel and storage devices, runs channel commands, and controls storage devices.

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 hierarchy

An arrangement of storage devices with different speeds and capacities. The levels of the storage hierarchy include main storage (memory, DASD cache), primary storage (DASD containing uncompressed data), migration level 1 (DASD containing data in a space-saving format), and migration level 2 (tape cartridges containing data in a space-saving format). See also primary storage, migration level 1, migration level 2, object storage hierarchy.

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.

storage subsystem

A storage control and its attached storage devices. See also tape subsystem.

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.

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 z/OS, this function is provided by DFSMS, DFSORT, and RACF. See also system-managed storage.

system-managed tape library

A collection of tape volumes and tape devices, defined in the tape configuration database. A system-managed tape library can be automated or manual. See also tape library.

system management facilities (SMF)

A component of z/OS that collects input/output (I/O) statistics, provided at the data set and storage class levels, which helps you monitor the performance of the direct access storage subsystem.

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.

tape library

A set of equipment and facilities that support an installation's tape environment. This can include tape storage racks, a set of tape drives, and a set of related tape volumes mounted on those drives. See also system-managed tape library.

tape mount management

The methodology used to optimize tape subsystem operation and use, consisting of hardware and software facilities used to manage tape data efficiently.

tape storage group

A type of storage group that contains system-managed private tape volumes. The tape storage group definition specifies the system-managed tape libraries that can contain tape volumes. See also storage group.

tape subsystem

A magnetic tape subsystem consisting of a controller and devices, which allows for the storage of user data on tape cartridges. Examples of tape subsystems include the IBM 3490 and 3490E Magnetic Tape Subsystems.

tape volume

A tape volume is the recording space on a single tape cartridge or reel. See also volume.

temporary data set

An uncataloged data set whose name begins with & or &&, that is normally used only for the duration of a job or interactive session. Contrast with permanent data set.

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.

time sharing option (TSO)

A function of the z/OS operating system that provides interactive time sharing from remote terminals.

TSO

See time sharing option

virtual input/output (VIO) storage group

A type of storage group that allocates data sets to paging storage, which simulates a DASD volume. VIO storage groups do not contain any actual DASD volumes. See also storage group.

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.

VMA

See volume mount analyzer

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.

volume mount analyzer

A program that helps you analyze your current tape environment. With tape mount management, you can identify data sets that can be redirected to the DASD buffer for management using SMS facilities.

VSAM

See virtual storage access method

weighted average

DASD space, including free space, which contains not only the data sets generated on primary storage, but also the recalled data sets. During the time of the analysis, this DASD space must be large enough to contain the data sets that will be generated or recalled. The value is calculated over time.