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

contains no named subsets. (2) In this book, thecomponents of an object are usually referred to as theobject’s data component and index component. Also,the cluster, data, or index fields of a subrecord.compress. (1) To reduce the amount of storagerequired for a given data set by having the systemreplace identical words or phrases with a shorter tokenassociated with the word or phrase. (2) To reclaim theunused and unavailable space in a partitioned data setthat results from deleting or modifying members bymoving all unused space to the end of the data set.compressed format. A particular type ofextended-format data set specified with the(COMPACTION) parameter of data class. VSAM cancompress individual records in a compressed-formatdata set. SAM can compress individual blocks in acompressed-format data set. See compress.concurrent copy. A function to increase theaccessibility of data by enabling you to make aconsistent backup or copy of data concurrent with theusual application program processing.construct. One of the following: data class, storageclass, management class, storage group, aggregategroup, base configuration.control area (CA). A group of control intervals used asa unit for formatting a data set before adding recordsto it. Also, in a key-sequenced data set, the set ofcontrol intervals pointed to by a sequence-set indexrecord; used by VSAM for distributing free space andfor placing a sequence-set index record adjacent to itsdata.control interval (CI). A fixed-length area of auxiliarystorage space in which VSAM stores records. It is theunit of information (an integer multiple of block size)transmitted to or from auxiliary storage by VSAM.coupling facility (CF). The hardware that provideshigh-speed caching, list processing, and lockingfunctions in a Parallel Sysplex.CRA.CVAF.DSee catalog recovery areaCommon VTOC access facility.DADSM. The direct access space managementprogram that maintains the VTOC, VTOCIX, and spaceon a volume.Data Facility Storage Management SubsystemTransactional VSAM Services (DFSMStvs). An IBMlicensed program for running batch VSAM processingconcurrently with CICS online transactions. DFSMStvsusers can run multiple batch jobs and onlinetransactions against VSAM data, in data sets defined asrecoverable, with concurrent updates. DFSMStvs is alicensed component of DFSMS.DASD volume. A DASD space identified by acommon label and accessed by a set of relatedaddresses. See also volume primary storage, migrationlevel 1, migration level 2.data class. A collection of allocation and spaceattributes, defined by the storage administrator, that areused to create a data set.data component. The part of a VSAM data set,alternate index, or catalog that contains the object’sdata records.data entry. A catalog entry that describes the datacomponent of a cluster, alternate index, page spaces, orcatalog. A data entry contains the data component’sattributes, allocation and extent information, andstatistics. A data entry for a cluster’s or catalog’s datacomponent can also contain the data component’spasswords and protection attributes.Data Facility Sort. An IBM licensed program that is ahigh-speed data processing utility. DFSORT provides anefficient and flexible way to handle sorting, merging,and copying operations, as well as providing versatiledata manipulation at the record, field, and bit level.data set. In DFSMS, the major unit of data storage andretrieval, consisting of a collection of data in one ofseveral prescribed arrangements and described bycontrol information to which the system has access. Innon-z/OS UNIX System Services/MVS environments,the terms data set and file are generally equivalent andsometimes are used interchangeably. See also file.data set control block (DSCB). A control block in theVTOC that describes data set characteristics.DBCS.See double-byte character setdefault device geometry. Part of the SMS baseconfiguration, it identifies the number of bytes pertrack and the number of tracks per cylinder forconverting space requests made in tracks or cylindersinto bytes, when no unit name has been specified.default management class. Part of the SMS baseconfiguration, it identifies the management class thatshould be used for system-managed data sets that donot have a management class assigned.default unit. Part of the SMS base configuration, itidentifies an esoteric (such as SYSDA) or generic (suchas 3390) device name. If a user omits the UNITparameter on the JCL or the dynamic allocationequivalent, SMS applies the default unit if the data sethas a disposition of MOD or NEW and is notsystem-managed.DES.See data encryption standard516 z/OS V1R6.0 DFSMS Access Method Services for Catalogs