Space on a sequential-access storage volume becomes reclaimable as files expire or are deleted from the volume. Reclamation processing involves consolidating the remaining data from many sequential-access volumes onto fewer new sequential-access volumes.
About this task
Files become obsolete because of aging or limits on the number of versions of a file. Space in volumes in active-data pools also becomes reclaimable as updated files are added to the pools and as older file versions are deactivated. In reclamation processing, the server rewrites files on the volume being reclaimed to other volumes in the storage pool, making the reclaimed volume available for reuse.
The server reclaims the space in storage pools based on a reclamation threshold that you can set for each sequential-access storage pool. When the percentage of space that can be reclaimed on a volume rises above the reclamation threshold, the server reclaims the volume.
- Storage pools that are defined with the NETAPPDUMP, the CELERRADUMP or the NDMPDUMP data format cannot be reclaimed. However, you can use the MOVE DATA command to move data out of a volume so that the volume can be reused. The volumes in the target storage pool must have the same data format as the volumes in the source storage pool.
- Storage pools that are defined with a CENTERA device class cannot be reclaimed.
- Reclaiming volumes with the most reclaimable space
If you have been running with a high reclamation threshold and decide you need to reclaim volumes, you can lower the threshold in several steps. Lowering the threshold in steps ensures that volumes with the most reclaimable space are reclaimed first. - Starting reclamation manually or in a schedule
To gain more control over how and when the reclamation process occurs, you can use the RECLAIM STGPOOL command. You can also specify the maximum amount of time a reclamation process takes before it is automatically canceled. - Optimizing drive usage using multiple concurrent reclamation processes
Multiple reclamation processes run concurrently, which makes better use of your available tape drives or FILE volumes. - Reclaiming volumes in a storage pool with one drive
When a storage pool has only one mount point (that is, just one drive) available to it through the device class, data cannot be reclaimed from one volume to another within that same storage pool. To reclaim volumes in a storage pool that has only one drive, you can define a reclamation storage pool and use it for temporary storage of reclaimed data. - Reducing the time to reclaim tape volumes with high capacity
When a storage pool uses tape volumes with high capacity, reclamation processes might run for a long time if the drives are relatively slow at positioning tapes. There are steps that you can take to reduce overall process time. 
Reclamation of write-once, read-many (WORM) media
Reclamation of WORM volumes does not mean that you can reuse this write-once media. However, reclamation does allow you to make more library space available.- Controlling reclamation of virtual volumes
When virtual volumes (volumes with the device type of SERVER) in a primary storage pool are reclaimed, the client data stored on those volumes is sent across the network between the source server and the target server. As a result, the reclamation process can tie up your network resources. - Reclaiming copy storage pools and active-data pools
On-site and off-site volumes in copy storage pools and active-data pools are reclaimed when the amount of unused space exceeds the reclamation threshold. When reclamation occurs and how reclamation processing is done depends on whether the volumes are marked as off-site. - How collocation affects reclamation
If collocation is enabled and reclamation occurs, the server tries to move the files for each client node, group of client nodes or client file space onto a minimal number of volumes.