Tivoli® Storage Manager policies are rules that determine how the client data is stored and managed. The rules include where the data is initially stored, how many backup versions are kept, how long archive copies are kept, and more.
You can have multiple policies and assign the different policies as needed to specific clients, or files. Policy assigns a location in server storage where data is initially stored. Server storage is divided into storage pools that are groups of storage volumes and can include disk and tape volumes.
When you install Tivoli Storage Manager, you have a default policy that you can use. For details about this default policy, see Reviewing the standard policy. You can modify this policy and define policies.
A client can restore any version of a file that is kept on the Tivoli Storage Manager server.
You can copy a backup set onto compatible portable media, which you can take directly to the client for rapid recovery without the use of a network and communicating with the Tivoli Storage Manager server.
The migration process is also called hierarchical storage management (HSM). After migration is configured, the process is transparent to the users. Files are migrated and recalled automatically.
A policy determines when files are considered for automatic migration. On UNIX or Linux systems that support the Tivoli Storage Manager for Space Management program, the policies determine whether files must be backed up to the server before it is migrated. Space management is also integrated with backup. If the file to be backed up is already migrated to server storage, the file is backed up from there.
Figure 1 shows how a policy is part of the Tivoli Storage Manager process for storing client data.
The steps in the process are as follows:
The storage pool can be a group of disk volumes, or tape volumes.
The Tivoli Storage Manager server saves information in its database about each file that it backs up, archives, or migrates.
If you set up server storage in a hierarchy, Tivoli Storage Manager can later migrate the file to a storage pool different from the one where the file was initially stored. For example, you might want to set up server storage so that Tivoli Storage Manager migrates files from a disk storage pool to tape volumes in a tape storage pool.
Files remain in the storage pools until they expire and expiration processing occurs, or until they are deleted on the server. A file expires because of criteria that are set in the policy. For example, the criteria include the number of file versions that are allowed and the number of days that have elapsed since a file was deleted from a client-node file system. If data retention protection is activated, an archive object cannot be inadvertently deleted.