To enable clients to restore backed-up files to a specific point in time, you must set up the backup copy group differently from the STANDARD. The Versions Data Exists, Versions Data Deleted, and Retain Extra Versions parameters work together to determine over what time period a client can perform a point-in-time restore operation.
For example, you decide to ensure that clients can choose to restore files from anytime in the previous 60 days. In the backup copy group, set the Retain Extra Versions parameter to 60 days. More than one backup version of a file may be stored per day if clients perform selective backups or if clients perform incremental backups more than once a day. The Versions Data Exists parameter and the Versions Data Deleted parameter control how many of these versions are kept by the server. To ensure that any number of backup versions are kept for the required 60 days, set both the Versions Data Exists parameter and the Versions Data Deleted parameter to NOLIMIT. This means that the server essentially determines the backup versions to keep based on how old the versions are, instead of how many backup versions of the same file exist.
Keeping backed-up versions of files long enough to allow clients to restore their data to a point in time can mean increased resource costs. Requirements for server storage increase because more file versions are kept, and the size of the server database increases to track all of the file versions. Because of these increased costs, you may want to choose carefully which clients can use the policy that allows for point-in-time restore operations.
Clients need to run full incremental backup operations frequently enough so that TSM can detect files that have been deleted on the client file system. Only a full incremental backup can detect whether files have been deleted since the last backup. If full incremental backup is not done often enough, clients who restore to a specific time may find that many files that had actually been deleted from the workstation get restored. As a result, a client's file system may run out of space during a restore process.