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Guidelines for retaining datafile backups and archive logs

My question is about backup and recovery. Is there a guideline for the length of retention of datafile backups and archive logs onsite? We keep only a day's worth of backup and archive log onsite and I feel it's too little. The offsite copies are retained for about a month.

My fear is when there is a need to get a backup copy, it might take at least 24 hrs for us to retrieve the copy. Are there any white papers or guidelines that you can point me to?

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The initial guidelines are dictated by your recovery requirements. How quick does your database have to be up and running in the event of a failure? The sooner you need your database up and running, the more often you will need to take backups. For example, it can take too long to roll forward a month's worth of changes. So a weekly or a daily backup is required. Or, the solution might be to employ RMAN's incremental backups.

How often should you keep your backups around? Well, you definitely need your latest backup and all archived redo logs generated since that backup. Many DBAs like to have three generations on hand. That would be your current backup, the previous backup, and the backup before that. This way, if there is a problem with the current backup, you can go back to the previous backup, etc. The number of generations of your backups is dictated by your site's policies. Typically, the number '3' is used here for many people.

As for offsite backups, I like to make sure that I have copies of my backup both offsite and onsite. In the event of a failure, I would only use my onsite backups. It simply takes too long to go to your offsite location, locate the backup tapes, bring them back to your site, and then get the backups off those tapes. It is much better if the onsite backups are available. In my opinion, the offsite backups would only be used if you lose your facility and have to relocate to another facility. In that scenario, your onsite backups are most likely unavailable as well so you are left with your offsite backups.

This was first published in March 2004

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