5.2 How to monitor and manager TSM Space Reclamation Process ?


What is TSM Reclamation process ?

Reclamation is the server process of consolidating files from several volumes onto one volume. You can set the reclamation threshold when you define or update the storage pool.
The server reclaims the space in storage pools according to 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.

Space on a sequential volume becomes reclaimable as files expire or are deleted from the volume. Reclamation is the process of reclaiming this space. For example, files become obsolete because of aging or limits on the number of versions of a file.

When the percentage of reclaimable space exceeds a specified level, the reclamation threshold, the volume is eligible for reclamation. The server checks at least once per hour whether reclamation is needed and begins space reclamation for eligible volumes. You can set a reclamation threshold for each sequential access storage pool when you define or update the pool.

When multiple volumes are eligible for reclamation, Tivoli Storage Manager reclaims the eligible volumes in random order.


TSM Reclamation
                                                   100%                 40%               30%                    70%
Image Source: IBM

Space within aggregate files is also reclaimed during the reclamation process. An aggregate is a physical file that contains multiple logical files that are backed up or archived from a client in a single transaction. During reclamation, unused space from expired or deleted logical files is removed as the aggregate file is copied to another volume.

Also Read: 15 tips to efficiently use the tape drive resources

When collocation is not used, Automatic data movement also frees up space on tape volumes by consolidating active data from fragmented tape volumes onto a single volume, leaving the original volumes available for reuse. This process is also known as reclamation. For each tape storage pool, you define a reclamation threshold, which indicates the amount of space consumed by data that is no longer valid before triggering reclamation. Specify a value not less than 50% to avoid tape volume reclamation to multiple volumes.

Reclamation is defined as the process of consolidating the remaining data from sequential access volumes onto fewer, new sequential access volumes.
  • A lower threshold results in more tapes and faster reclamation time.
  • A higher threshold results in fewer tapes and longer reclamation time.
  • You use the RECLAIM STGPOOL command to initiate an automatic drive reclamation for a sequential access primary or copy storage pool.
  • Empty tapes move back to scratch or private pools.
  • Reclamation of an active-data pool recovers space that inactive and deleted files use.
Space Reclamation can be configured automatically and manually. To configure automatic reclamation, update the storage pool with RECLAIM parameter. To run a manual reclamation, use the following command as shown below.
reclaim stgpool stgpoolname reclaim=60

Offsite Reclamation on Copy Storage Pools

The tape volumes which are sent to offsite for DR purposes can also be reclaimed without bringing them back to onsite, this process is generally known as offsite reclamation (to know more about this click link). Volumes with the access value of OFFSITE are eligible for reclamation if the amount of empty space on a volume exceeds the reclamation threshold for the copy storage pool or active-data pool. The default reclamation threshold for copy storage pools and active-data pools is 100%, which means that reclamation is not performed.

Also Read: How to configure TSM Server Administrative Schedules ?

To cancel the automatic offsite reclamation on copy storagepools, set reclamation threshold to 100% with the define or update stgpool command. Use the OFFSITERECLAIMLimit=0 parameter with the reclaim stgpool command.
update stgpool copystgppols OFFSITERECLAIMLimit=0

You should schedule offsite reclamation process by using reclaim stgpool command when you have less pressure on the TSM server. 

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NEXT: 5.3 IBM Tivoli Storage Manager Collocation Overview
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