When you define a storage pool that uses disk random access volumes, you can choose to enable or disable cache. When you use cache, a copy of the file remains on disk storage even after the file is migrated to the next pool in the storage hierarchy, for example, to tape. The file remains in cache until the space it occupies is needed to store new files.
Using cache can improve how fast a frequently accessed file is retrieved. Faster retrieval can be important for clients that are 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.