This section describes a sample backup approach for a very large Oracle database using daily partial backups.
In this example, the database is too large for a complete daily offline or online backup and has to be available 24 hours a day on five working days. Therefore, the backup is spread over two days (part A and part B) and performed online. It runs during the night, as this is the only time when a low transaction load can be expected.
Backup Approach for a Very Large Database with Partial Backups A and B
This strategy is more error-prone than the first example, because the database administrator is responsible for the correct distribution of the data to the partial backups, A and B. The risk of losing data is even higher, because online backups are only consistent in combination with redo information.
The number of tapes required for the data backup is 40+x, where x is the number of reserve tapes. For security reasons, an additional complete offline backup is performed at the weekend. If this strategy is used with a retention period of seven days, only four generations of backups are available. The redo log files are even more important than in the first example, as the online backups are worthless without them. It is essential to back up the redo data twice. Therefore, you need 2 x (19 + x) tapes for redo information, where x is the number of reserve tapes.
It is possible with brarchive -cds to automatically create two copies of backup data using a single set of tapes.