System Programmer Reference › Managing Tape and DASD Resources › Handling Tapes and DASD Resources for Backup and MPC Jobs › Tape Remounts › Reducing Tape Remounts

Reducing Tape Remounts

If you specify that CA VM:Backup should reduce remounts, CA VM:Backup does not ask the operator to remount tapes when it detects a change in or a problem with a minidisk or when performing domain-level physical incremental backups. Instead, CA VM:Backup does the following:

• If the backup of the minidisk begins on the current tape, CA VM:Backup repositions the tape to the point at which the backup of the minidisk begins and starts backing up the next eligible minidisk.
• If the backup of the minidisk begins on a previous tape, CA VM:Backup repositions the current tape to the beginning, writes a cancellation (CAN1) record, and starts backing up the next eligible minidisk. The CAN1 record tells CA VM:Backup that this backup of the minidisk is not valid; CA VM:Backup will not restore this version of the minidisk during ordinary restores.

  The VMBSCAN and VMBRITS utilities recognize the CAN1 record. VMBRITS can restore portions of this invalid backup, but both VMBSCAN and VMBRITS issue this message when they encounter the CAN1 record:

  018I CANCELLATION RECORD FOUND FOR userid vaddr; THIS IS NOT THE VALID BACKUP COPY OF THIS MINIDISK.

  If you are restoring from a CMS format backup and VMBRITS encounters a CAN1 record, the minidisk being restored might be left in an unfinished state.

Reducing tape mounts can save time; however, it increases tape usage.

CA VM:Backup might still remount tapes under the following conditions:

• When it restarts a job from checkpoint.
• When you use CA VM:Tape with the AUTOPICK ACCEPT feature, and a tape other than the one selected by AUTOPICK is mounted. CA VM:Backup must remount the previous tape to correct tape chaining information in that tape's trailer labels unless you disable this feature. For more information, see the following section on Tape Chaining.