In this example, the size of the database is less than 200 GB, and daily backups are possible. As the SAP System does not have to be available after 18:00, the backup can be performed offline. Alternatively, the backup can be performed online at a time when the transaction load is low, such as overnight. If DLT drives are used, a full backup of the data (without redo information) fits onto two tapes.

To be able to deal with a faulty backup, several generations of backups must be available. In this example, the retention period is set to 28 days, so 27 backup generations are always available. The tape pool must also contain several reserve tapes. In this case, 56 + x tapes are required for data backup. The additional x tapes – approximately 20% of the required number – function as a reserve in case the amount of data to be backed up greatly increases, an extra unplanned backup becomes necessary, or a tape fails.

The redo information generated during the day – buffered on a separate disk that is as large as possible – is also backed up every day using a separate tape pool. As this data is necessary to recover a database after restoring a data backup, the retention period for the tapes must be no less than the retention period for the actual data backup. Particularly in the case of an online backup, you must always back up redo information directly after the data backup.

As the redo data is much more dynamic than the actual data, even more reserve tapes are required. For this example, 52+x tapes are needed, where x is the number of reserve tapes for redo data. For security reasons, we recommend you to back up redo information twice, so the total number of tapes required is 2 x (52 + x). The actual number of tapes depends on the hardware implemented and the tape capacity available: