Progress
Database Administration
Guide and Reference


Time Needed For Recovery

How you archive and restore data depends on how long you can spend recovering the database if it becomes unavailable. Table 6–6 provides examples.

Table 6–6: Availability and Recovery Time 
If You Can Spend . . .
Then Save Changes In . . .
Four hours recovering
A duplicate database on warm standby. Use roll-forward recovery to keep the standby database current with the production database.
Eight hours recovering
A full backup and one incremental or AI file.
Sixteen hours recovering
A full backup and several incremental backups or AI files.
Twenty-four hours recovering
A full backup and any number of incremental or AI files.

You might decide to perform daily backups of the AI files instead of performing incremental backups. However, backing up the AI files backs up whole transactions, not just the blocks that have changed since the most recent backup. Therefore, performing and restoring AI file backups might require more space and time than incremental backups.

Before deciding to back up the AI files every day, consider that recovering the database from many smaller AI files is more intricate than recovering from few larger AI files.

In addition to the time required to recover the database, you must allow time to repair hardware, file systems, system disks, and other system components. If you can afford no more than eight hours to recover your entire system, you should consider using redundant hardware components, such as mirrored disks, and a high availability system with failover support.


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