Reusing tapes

To ensure an adequate supply of tapes, you can expire old files, reclaim volumes, and delete volumes that reach end of life. You can also maintain a supply of scratch volumes.

1. Delete unnecessary client data by regularly running expiration processing. Expiration processing deletes data that is no longer valid either because it exceeds the retention specifications in the policy or because users or administrators deleted the active versions of the data.
2. Reuse volumes in storage pools by running reclamation processing.

   Reclamation processing consolidates any unexpired data by moving it from multiple volumes onto fewer volumes. The media can then be returned to the storage pool and reused.

3. Reuse volumes that contain outdated database backups or exported data that is no longer required by deleting volume history.

   Before the server can reuse volumes that are tracked in the volume history, you must delete the volume information from the volume history file by issuing the DELETE VOLHISTORY command.

   Tip: If your server uses the disaster recovery manager (DRM) function, the volume information is automatically deleted during MOVE DRMEDIA command processing.
4. Determine when tape volumes reach end of life. You can use the server to display statistics about volumes, including the number of write operations that are completed on the media and the number of write errors. Private volumes and scratch volumes display the following statistical data:

   Private volumes

   For media initially defined as private volumes, the server maintains this statistical data, even as the volume is reclaimed. You can compare the information with the number of write operations and write errors that are recommended by the manufacturer.

   Scratch volumes

   For media initially defined as scratch volumes, the server overwrites this statistical data each time the volumes are reclaimed.

5. Reclaim any valid data from volumes that reach end of life. If the volumes are in automated libraries, check them out of the volume inventory. Delete private volumes from the database with the DELETE VOLUME command.
6. Ensure that volumes are available for tape rotation so that the storage pool does not run out of space. You can use the Operations Center to monitor the availability of scratch volumes. Ensure that the number of scratch volumes is high enough to meet demand. For more information, see Maintaining a supply of volumes in a library that contains WORM media.
   WORM media: Write Once Read Many (WORM) drives can waste media when the server cancels transactions because volumes are unavailable to complete the backup operation. After the server writes to WORM volumes, the space on the volumes cannot be reused, even if the transactions are canceled (for example, if a backup is canceled because of a shortage of media in the device). To minimize wasted WORM media, complete the following actions:

   1. Ensure that the maximum number of scratch volumes for the device storage pool is at least equal to the number of storage slots in the library.
   2. Check enough volumes into the device's volume inventory for the expected load.

   If most backup operations are for small files, controlling the transaction size can affect how WORM platters are used. Smaller transactions mean that less space is wasted when a transaction such as a backup operation must be canceled. Transaction size is controlled by a server option, TXNGROUPMAX, and a client option, TXNBYTELIMIT.