z/OS V1R6.0 DFSMS Access Method Services for Catalogs

DFSMS environment. An environment that helpsautomate and centralize the management of storage.This is achieved through a combination of hardware,software, and policies. In the DFSMS environment forMVS, this function is provided by DFSMS, DFSORT,and RACF. See also system-managed storage.DFSMSdfp. A DFSMS functional component or baseelement of z/OS, that provides functions for storagemanagement, data management, program management,device management, and distributed data access.DFSMShsm. A DFSMS functional component or baseelement of z/OS, used for backing up and recoveringdata, and managing space on volumes in the storagehierarchy.DFSMShsm-managed volume. (1) A primary storagevolume, which is defined to DFSMShsm but whichdoes not belong to a storage group. (2) A volume in astorage group, which is using DFSMShsm automaticdump, migration, or backup services. Contrast withsystem-managed volume, DFSMSrmm-managed volume.DFSMSrmm-managed volume. A tape volume that isdefined to DFSMSrmm. Contrast with system-managedvolume, DFSMShsm-managed volume.DFSMStvs. See Data Facility Storage ManagementSubsystem Transactional VSAM Services.DFSORT.See data facility sortdictionary. A table that associates words, phrases, ordata patterns to shorter tokens. The tokens replace theassociated words, phrases, or data patterns when a dataset is compressed.direct access. The retrieval or storage of data by areference to its location in a data set rather than relativeto the previously retrieved or stored data. See alsoaddressed direct access and keyed direct access.double-byte character set (DBCS). A 2-bytehexadecimal value which can be used to represent asingle character for languages that contain too manycharacters or symbols for each to be assigned a 1-bytehexadecimal value.DSCB.See data set control blockdual copy. A high availability function made possibleby nonvolatile storage in some models of the IBM 3990Storage Control. Dual copy maintains two functionallyidentical copies of designated DASD volumes in thelogical 3990 subsystem, and automatically updates bothcopies every time a write operation is issued to thedual copy logical volume.dummy storage group. A type of storage group thatcontains the serial numbers of volumes no longerconnected to a system. Dummy storage groups allowexisting JCL to function without having to be changed.See also storage group.dynamic allocation. The allocation of a data set orvolume by the use of the data set name or volumeserial number rather than by the use of informationcontained in a JCL statement.EEnhanced Capacity Cartridge System Tape. Cartridgesystem tape with increased capacity that can only beused with 3490E tape subsystems. Contrast withCartridge System Tape.entry. A collection of information about a catalogedobject in a master or user catalog. Each entry resides inone or more 512-byte records.entry name. A unique name for each component orobject as it is identified in a catalog. The entry name isthe same as the dsname in a DD statement thatdescribes the object.entry sequence. The order in which data records arephysically arranged (according to ascending RBA) inauxiliary storage, without respect to their contents.Contrast to key sequence.entry-sequenced data set (ESDS). In VSAM, a data setwhose records are loaded without respect to theircontents, and whose RBAs cannot change. Records areretrieved and stored by addressed access, and newrecords are added at the end of the data set.ESDS.See entry-sequenced data setesoteric unit name. A name used to define a group ofdevices having similar hardware characteristics, such asTAPE or SYSDA. Contrast with generic unit name.expiration. (1) The process by which data sets orobjects are identified for deletion because theirexpiration date or retention period has passed. OnDASD, data sets and objects are deleted. On tape, whenall data sets have reached their expiration date, the tapevolume is available for reuse. (2) In DFSMSrmm, allvolumes have an expiration date or retention period setfor them either by vital record specification policy, byuser-specified JCL when writing a data set to thevolume, or by an installation default. When a volumereaches its expiration date or retention period, itbecomes eligible for release.export. To create a backup or portable copy of aVSAM cluster, alternate index, or integrated catalogfacility user catalog.extended addressability. The ability to create andaccess a VSAM data set that is greater than 4 GB inGlossary 517