You want to free as many ASM2 tapes as possible, perhaps because you have changed to backups on disk, phasing out tapes, or require additional scratch tapes. You can identify tapes with a large proportion of free space and consolidate them onto fewer tapes by using the $MAINT and Forward Merge jobs in combination.
First, run a $MAINT job to remove any files that are due for deletion. Your site should run a $MAINT job regularly, recommended weekly. As part of the normal $MAINT job you will be provided a list of tapes that are good candidates for consolidation. You can alter the minimum utilization reporting by adjusting the control statement TAPEUTIL-PCT(nn). ((nn) defines the minimum utilization percentage cutoff, the default is 20%.) When the percentage utilized on a tape is below the TAPEUTIL-PCT specified, then a merge request is written to the FMQUEUE DD file. This file that will be used as input to a Forward Merge job.
The second step is to run a Forward Merge job. It will read the tapes on the list (The FMQUEUE dataset) created by the $MAINT job in the previous step and consolidate all of the files from the partially used tapes onto fewer tapes. The FMQUEUE list from the previous step may be divided into smaller lists to be run one at a time. The Forward Merge procedure ASM2FMRG, is fully documented in section 14.6 of the CA ASM2 System Reference Guide.
Do not execute a Forward merge process or a $MAINT process while IXR is executing due to the enqueues on the ASM2 IPC and JNL files. This could slow down potential reloads. It is recommended that this process be executed during a very low activity time or off shift when IXR can be brought down