System Programmer Reference › Managing Tape and DASD Resources › Handling Tapes and DASD Resources for Backup and MPC Jobs › Writing to Tapes › Writing to Backup Tapes and MPC Output Tapes

Writing to Backup Tapes and MPC Output Tapes

When a tape is mounted for use in a backup or MPC job, CA VM:Backup verifies that the tape's label is valid, it is an expired or new tape, and it can be used in the job. If the tape can be used in the job, CA VM:Backup rewrites the tape labels to reflect the new information for this job. Included in this new information is a new tape expiration date. However, CA VM:Backup updates only the tape labels at this time; it does not update the resource pool information until the end of the backup job.

If the CA VM:Backup system terminates abnormally after the tape labels have been rewritten but before the tape is dismounted, and the CA VM:Backup system is then restarted, the expiration date in the tape label will not match the one listed in the resource pool. In addition, the resource pool will indicate that this tape is available for use by any backup or MPC job. CA VM:Backup uses the resource pool information to select tapes to use for backup and MPC jobs.

If this tape is mounted for a subsequent backup or MPC job, CA VM:Backup will again verify that the tape labels are valid and that the tape is expired or new. If the tape expiration date previously written in the tape labels has not yet been reached and a TAPEXPDT record exists in the VMBACKUP CONFIG file, CA VM:Backup will request permission from the tape operator to overwrite the tape. If the tape operator specifies that the tape can be used, CA VM:Backup writes to the tape. For information about this record, see TAPEXPDT Record.

If the TAPEXPDT record is not specified in the VMBACKUP CONFIG file, CA VM:Backup does not ask for permission to overwrite the tape; it rejects the tape and does not use it in the job. CA VM:Backup then selects another tape to use in the job and asks the tape operator to mount the new tape. Before the newly selected tape is mounted, CA VM:Backup may ask that the operator mount the previously used tape again so that it can update the trailer label of that tape to reflect the newly selected tape. CA VM:Backup writes tape chaining information to trailer labels by default, but you can disable this feature. For more information, see Tape Chaining.

If CA VM:Backup resource pools are being used to manage tapes and CA VM:Backup asks permission to override a tape expiration date, CA VM:Backup should not be allowed to overwrite the data on a tape without first verifying that the tape does not contain valid data.

If CA VM:Backup is interfaced with CA VM:Tape and CA VM:Backup requests permission to override a tape expiration date, CA VM:Backup can be allowed to overwrite the tape.