Reusing DASDTapes

Products

• VM:Backup for z/VM

Issue/Introduction

Trying to get a "sweet spot" for the amount of DASDTape required and better understand how they are allocated or reclaimed.

 

Environment

Release : 3.6

Component : CA VM:Backup for z/VM

Resolution

The VMBACKUP DASDTAPE QUERY command shows free/available space with data occupied by already expired tapes included in those values.

DASDTapes are allocated or reclaimed (from expired DASDTapes) as a backup job runs.

When a DASDTape needs to be allocated (mounted) for a backup job, VM:Backup determines if there is sufficient true unallocated space on the TAPEDISK to create a new DASDTape volume. If there is not, VM:Backup scans the current TAPEDISK to see if there is an expired DASDTape that can be reused. If there's not, then VM:Backup moves to the next TAPEDISK and repeats the process until a DASDTape can be allocated or the job is put on hold because a DASDTape cannot be allocated.