How to reclaim tape volumes which are in offsite vault location (Offsite Reclamation)


Volumes with the access value of off-site 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.

When an off-site volume is reclaimed, the files on the volume are rewritten to a read/write volume. Effectively, these files are moved back to the on-site location. The files may be obtained from the off-site volume after a disaster, if the volume has not been reused and the database backup that you use for recovery references the files on the off-site volume.

How Offsite Reclamation Works ?

  • The server determines which files on the volume are still valid. The server obtains these valid files from a primary storage pool or, if necessary, from an on-site volume of a copy storage pool or active-data pool.
  • The server writes the files to one or more volumes in the copy storage pool or active-data pool and then updates the database. If a file is an aggregate with unused space, the unused space is removed during this process.
Also Read: Monitoring and Managing Tape Volumes
  • A message is issued indicating that the off-site volume was reclaimed.
  • For a single storage pool, the server reclaims all off-site volumes that are eligible for reclamation at the same time. Reclaiming all the eligible volumes at the same time minimizes the tape mounts for primary storage pool volumes.
  • For example, to limit offsite reclamation on a copy storage pool, update storage pool with this below command.
          update stgpool <copypoolname> offsitereclaimlimit=<nolimit/number>

          NOLimit
          Specifies that you want to have the space reclaimed in all of your
          offsite volumes.

         Number
         Specifies the number of offsite volumes to have their space
         reclaimed. You can specify an integer from 0 to 99999. A value of

         zero means that none of the offsite volumes will be reclaimed. 

Controlling when reclamation occurs for off-site volumes

If you send copy storage pool volumes off-site, you can control reclamation by adjusting the reclamation threshold. Suppose you plan to make daily storage pool backups to a copy storage pool, then mark all new volumes in the copy storage pool as offsite and send them to the off-site storage location. This strategy works well with one consideration if you are using automatic reclamation (the reclamation threshold is less than 100%). 

Each day's storage pool backups will create a number of new copy-storage pool volumes, the last one being only partially filled. If the percentage of empty space on this partially filled volume is higher than the reclaim percentage, this volume becomes eligible for reclamation as soon as you mark it off-site. 

Also Read: TSM Administrator Daily routine tasks

The reclamation process would cause a new volume to be created with the same files on it. The volume you take off-site would then be empty according to the Tivoli Storage Manager database. If you do not recognize what is happening, you could perpetuate this process by marking the new partially filled volume off-site.

One way to resolve this situation is to keep partially filled volumes on-site until they fill up. However, this would mean a small amount of your data would be without an off-site copy for another day.

If you send copy storage pool volumes off-site, it is recommended you control pool reclamation by using the default value of 100. This turns reclamation off for the copy storage pool. You can start reclamation processing at desired times by changing the reclamation threshold for the storage pool. To monitor off-site volume utilization and help you decide what reclamation threshold to use, enter the following command:

query volume * access=offsite format=detailed

Depending on your data expiration patterns, you may not need to do reclamation of off-site volumes each day. You may choose to perform off-site reclamation on a less frequent basis. 

For example, suppose you ship copy-storage pool volumes to and from your off-site storage location once a week. You can run reclamation for the copy-storage pool weekly, so that as off-site volumes become empty they are sent back for reuse.

Best Practices for running Offsite Reclamation

  • Back up your primary-storage pools to copy-storage pools or copy the active data in primary-storage pools to active-data pools.
  • Turn on reclamation for copy-storage pools and active-data pools by lowering the reclamation threshold for copy-storage pools below 100%. The default for active-data pools is 60.
Also Read: How to configure TSM Server Administrative Schedules ?
  • When reclamation processing completes, turn off reclamation by raising the reclamation thresholds to 100%. 
  • Mark any newly created copy-storage pool volumes and active-data pool volumes as off-site, and then move them to the off-site location.
This process ensures that the files on the new copy-storage pool volumes and active-data pool volumes are sent off-site, and are not inadvertently kept on-site because of reclamation.




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6 Responses to "How to reclaim tape volumes which are in offsite vault location (Offsite Reclamation)"

  1. If you send copy storage pool volumes off-site, it is recommended you control pool reclamation by using the default value of 100. This turns reclamation off for the copy storage pool. A good post indeed.
    storage reclamation

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  2. great explanation thanks a lot body

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  3. i am new to tsm... there is no communication between tsm server and offsite volumes but how the server knows perticular tapes are eligeble for reclaimation..? could you explain me anil...

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    Replies
    1. It is through database that TSM server manages i.e. TsM's own database which runs on IBM DB2.

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