This section contains information to be aware of when using magnetic disk devices for server storage. The sections give pointers to additional information.
When you define a storage pool that uses disk random access volumes, you can choose to enable or disable cache. Using cache can improve how fast a frequently accessed file is retrieved. When you use cache, a copy of the file remains on disk storage even after the file has been migrated to the next pool in the storage hierarchy (for example, to tape). Faster retrieval can be important for clients storing space-managed files. If the file needs to be accessed, the copy in cache can be used rather than the copy on tape. However, using cache can degrade the performance of client backup operations and increase the space needed for the database. For more information, see The Use of Cache on Disk Storage Pools.
As client files expire, the space they occupy is not freed for other uses until you run expiration processing.
Expiration processing deletes from the database information about any client files that are no longer valid according to the policies you have set. For example, suppose four backup versions of a file exist in server storage, and only three versions are allowed in the backup policy (the management class) for the file. Expiration processing deletes information about the oldest of the four versions of the file. The space that the file occupied in the storage pool becomes available for reuse.
You can run expiration processing by using one or both of the following methods:
When you backup the database or export server information, Tivoli Storage Manager records information about the volumes used for these operations in the volume history file. Tivoli Storage Manager does not allow you to reuse these volumes until you delete the volume information from the volume history file. To reuse volumes that have previously been used for database backup or export, use the DELETE VOLHISTORY command. For information about the volume history file, see Saving the Volume History File.
Note: | If your server is licensed for the DRM feature, the volume information is automatically deleted during MOVE DRMEDIA command processing. For additional information about DRM, see Chapter 20, Using Tivoli Disaster Recovery Manager. |