The format of a DASDtape is similar to that of a physical tape. Each DASDtape is a single file on a CMS-formatted minidisk. The filename is the volser of the DASDtape and the filetype is TAPE. You can define DASDtape minidisks on any supported DASD type. Block the minidisks at 4K-byte blocks. CA VM:Backup actually writes DASDtapes with simulated densities of 800, 1600, 6250, and 38K.
Like physical tapes, a DASDtape file consists of a standard label image, followed by one or more data blocks. The tape is terminated by a trailer label and double end-of-file (EOF) marks. The standard label allows the same date protection and verification fields as a standard label on a physical tape.
When a DASDtape volser is deleted from a resource pool or the pool is discarded, the DASDtapes are not automatically erased from the DASDtape minidisk. To clear the DASDtape minidisk of deleted DASDtapes, manually erase these files when CA VM:Backup is not running. If a subsequent backup or MPC job uses an expired DASDtape, the new data replaces the old DASDtape file.
When a DASDtape expires, the TAPE file is not automatically erased from the DASDtape minidisk. TAPE files are erased when more space is required during a job that writes to the DASDtape disk, provided they are not referenced in an existing catalog.
Unlike physical tapes, DASDtapes are managed entirely by CA VM:Backup, even if interfaced with CA VM:Tape. When you use DASDtapes, operator time and effort are no longer required for the management of tape volsers, tape initialization, and tape drive management because these tasks are only applicable for physical tapes.
Jobs are not restarted after DASDtape I/O errors.
Notes:
The following sections address some considerations for using DASDTapes.
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