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

allocation. Generically, the entire process of obtaininga volume and unit of external storage, and setting asidespace on that storage for a data set.alternate index (AIX). In systems with VSAM, akey-sequenced data set containing index entriesorganized by the alternate keys of its associated basedata records. It provides an alternate means of locatingrecords in the data component of a cluster on whichthe alternate index is based.alternate index cluster. The data and indexcomponents of an alternate index.alternate-index entry. In VSAM, a catalog entry thatcontains information about an alternate index. Analternate index entry points to a data entry and anindex entry to describe the alternate index’scomponents, and to a cluster entry to identify thealternate index’s base cluster. See also cluster entry.alternate-index record. In VSAM, a collection of itemsused to sequence and locate one or more data recordsin a base cluster. Each alternate-index record containsan alternate-key value and one or more pointers. Whenthe alternate index supports a key-sequenced data set,the pointer is the prime key value of each data record.When the alternate index supports an entry-sequenceddata set (ESDS), the RBA value of the data records isthe pointer. See also alternate index entry, alternate key,base cluster, and key.alternate key. One or more characters within a datarecord used to identify the data record or control itsuse. Unlike the prime key, the alternate key canidentify more than one data record. It is used to buildan alternate index or to locate one or more base datarecords with an alternate index. See also key and primekey.application. The use to which an access method is putor the end result that it serves; contrasted to theinternal operation of the access method.automated tape library data server. A deviceconsisting of robotic components, cartridge storageareas, tape subsystems, and controlling hardware andsoftware, together with the set of tape volumes thatreside in the library and can be mounted on the librarytape drives. Contrast with manual tape library. See alsotape library.automatic backup. (1) In DFSMShsm, the process ofautomatically copying data sets from primary storagevolumes or migration volumes to backup volumes. (2)In OAM, the process of automatically copying aprimary copy of an object from DASD, optical, or tapevolume to a backup volume contained in an objectbackup storage group.automatic class selection (ACS) routine. A proceduralset of ACS language statements. Based on a set of inputvariables, the ACS language statements generate thename of a predefined SMS class, or a list of names ofpredefined storage groups, for a data set.automatic data set protection (ADSP). In z/OS, a userattribute that causes all permanent data sets created bythe user to be automatically defined to RACF with adiscrete RACF profile.automatic secondary–space management. InDFSMShsm, the process of automatically deletingexpired migrated data sets, deleting expired recordsfrom the migration control data sets, and migratingeligible data sets from migration level 1 volumes tomigration level 2 volumes.availability. For a storage subsystem, the degree towhich a data set or object can be accessed whenrequested by a user.Bbackout. A request to remove all changes to resourcessince the last commit or backout or, for the first unit ofrecovery, since the beginning of the application.Backout is also called rollback or abort.backup. The process of creating a copy of a data set orobject to be used in case of accidental loss.backup control data set (BCDS). In DFSMShsm, aVSAM key-sequenced data set that containsinformation about backup versions of data sets, backupvolumes, dump volumes, and volumes under control ofthe backup and dump functions of DFSMShsm.backup-while-open (BWO). This makes a backupcopy of a data set while the data set is open for update.The backup copy can contain partial updates.base cluster. A key-sequenced data set orentry-sequenced data set over which one or morealternate indexes are built. See also alternate index entryand path.base configuration. The part of an SMS configurationthat contains general storage management attributes,such as the default management class, default unit, anddefault device geometry. It also identifies the systemsor system groups that an SMS configuration manages.basic catalog structure (BCS). The name of the catalogstructure in the catalog environment.BCDS.BCS.See backup control data setSee basic catalog structureblock size. (1) The number of data elements in ablock. (2) A measure of the size of a block, usuallyspecified in units such as records, words, computerwords, or characters. (3) Synonymous with blocklength. (4) Synonymous with physical record size.514 z/OS V1R6.0 DFSMS Access Method Services for Catalogs