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
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.