CA TLMS requires a BDAM Volume Master File which contains one 500-byte record for each tape volume in the tape library under the control of CA TLMS (including standard labeled, nonlabeled, bypass label processing and nonstandard labeled tape volumes). CA TLMS controls all tapes by volume serial number (VSN).
Access to the VMF is by the relative record BDAM technique. The relative record is derived from the volume serial number of the tape volume. This file may be blocked. Since tape VSNs are not restricted to a single consecutive numeric series, direct-access storage is conserved by using a file segmentation technique. Records exist in the VMF for all consecutive numbers within a file segment.
CA TLMS maintains an index of file segments in the Volume Master File in one or more segment records at the beginning of the file. One segment record can hold up to 23 file segment indexes. The Volume Master File will contain as many segment records as required to hold the file segment indexes.
A small number of skipped or missing VSNs does not require the definition of a new file segment. These numbers are defined as skipped when the file is built and dummy records are written to the file to maintain the relative record logic.
The VMF also contains records that are used to maintain multivolume data sets and multi-data set volumes. These are defined as auxiliary records. You can also reserve additional space for special disposition messages which are generated when specific tape data sets are closed.
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