IBM Tivoli Storage Manager, Version 7.1

How Tivoli Storage Manager reclamation works

You can set a reclamation threshold for a sequential-access storage pool when you define or update the pool. When the percentage of reclaimable space on a volume exceeds the reclamation threshold set for the storage pool, the volume is eligible for reclamation.

The server checks whether reclamation is needed at least once per hour and begins space reclamation for eligible volumes. During space reclamation, the server copies files that remain on eligible volumes to other volumes. For example, Figure 1 shows that the server consolidates the files from tapes 1, 2, and 3 on tape 4. During reclamation, the server copies the files to volumes in the same storage pool unless you have specified a reclamation storage pool. Use a reclamation storage pool to allow automatic reclamation for a storage pool with only one drive.

Remember: To prevent contention for the same tapes, the server does not allow a reclamation process to start if a DELETE FILESPACE process is active. The server checks every hour for whether the DELETE FILESPACE process has completed so that the reclamation process can start. After the DELETE FILESPACE process has completed, reclamation begins within one hour.

The server also reclaims space within an aggregate. An aggregate is a physical file that contains multiple logical files that are backed up or archived from a client in a single transaction. Space within the aggregate becomes reclaimable space as logical files in the aggregate expire, as files are deleted by the client, or as files become deactivated in active-data pools. The server removes unused space as the server copies the aggregate to another volume during reclamation processing. However, reclamation does not aggregate files that were originally stored in non-aggregated form. Reclamation also does not combine aggregates to make new aggregates. You can also reclaim space in an aggregate by issuing the MOVE DATA command. See Reclaiming space in aggregates by moving data for details.

Figure 1. Tape reclamation

The data from three separate tapes is combined on a single, other tape.

After the server moves all readable files to other volumes, one of the following occurs for the reclaimed volume:

If you have explicitly defined the volume to the storage pool, the volume becomes available for reuse by that storage pool.
If the server acquired the volume as a scratch volume, the server deletes the volume from the Tivoli® Storage Manager database.

Volumes that have a device type of SERVER are reclaimed in the same way as other sequential-access volumes. However, because the volumes are actually data stored in the storage of another Tivoli Storage Manager server, the reclamation process can consume network resources. See Controlling reclamation of virtual volumes for details about how the server reclaims these types of volumes.

Volumes in a copy storage pool and active-data pools are reclaimed in the same manner as a primary storage pool except for the following:

Off-site volumes are handled differently.
The server copies active files from the candidate volume only to other volumes in the same storage pool.

For details, see Reclaiming copy storage pools and active-data pools.

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