Re: Backup & recovery procedures on Oracle7 database

Hello, Jacques:

To ensure database recovery, ARCHIVELOG mode must be used.

This mode creates copies of online redo logs as they are filled.

To recover the database after a failure, you *must* have

	the most recent "hot" backup
	all archived redo logs
	all online redo logs that have not been archived

The "hot" backup is images of all data base files prepared while the data base iis running. The archived redo logs are prepared by the database while it is running, and the online redo logs are the two or more logs that the data base uses at all times.

All of these are required, so the online redo logs must be located on mirrored disks, and the archived redo logs and backup images must be in a "safe" place, which will be other than where the data base resides, since this is where your are expecting the failure.

The Oracle manual has an uncharacteristically clear explanation of the various failure modes and how to deal with each. In general, after figuring out which has occurred, the damaged area is restored from the "hot" backup and the redo logs are applied to recover the database to the point in time just prior to the failure.

You will also find that frequent exports will aid recovery from dropped tables and the like, but ARCHIVELOG mode is required for arbitrary point-in-time recovery.

Regards,

Gary

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| Gary Gapinski              | email: gapinski_at_lerc.nasa.gov |


| NASA Lewis Research Center | voice: +1 216 433 5251        |


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