Re: Oracle Archived logs?

On Wed, 26 Feb 2003 15:48:59 +0200, James wrote:

> Hi there
> A question I take online hotbackups of my database. The question I have is
> when do the archive logs become unnecessary?
>
> For example I make a hotbackup everyday but I'm also backing up every
> Archived log since I started performing hotbackups. Surely there must come a
> time when those old arechived logs are not needed. I don't want to back them
> all up cause I'm running out of space!! How do I find out which are needed?
> If I need them all why?
>
> I'm using oracle 9 on Win 2k.
>
> A BIG thanks in advance
> james

Technically, as soon as a new hot backup has completed, you can delete all archived logs produced from a time prior to the start of that hot backup -because in the event of performing a recovery, you would restore from your lsat hot backup, and roll it forward. And quite clearly, you don't need archives from before that backup to roll it forward.

However, you should give yourself some breathing room. What if your last hot backup turns out, on the day, to have been put onto corrupted media? You'd need to restore from a backup taken before the last one, and thus need all the archives from *that* backup forward, not the latest one.

Similarly, what do you do when a user asks you to restore data as it looked last week? If all you've got is archives since your last hot backup, all your prior backups are rendered useless... so a week-old restore is not possible.

So, what is technically feasible is not necessarily what is practically sensible. Ask yourself when you would never consider using a prior backup for a restore. If the backup taken three weeks ago is considered by you to be utterly redundant, then you need only retain three weeks' of archives. Everything else can go.

At one place I worked, they retained 7 days' of archives on disk, aged them out thereafter onto tape, and rotated tapes such that, if we'd needed to, we could have restored a backup taken 5 months previously, and completely recovered it. Your business requirements might not be so onerous, however.

Regards
HJR Received on Wed Feb 26 2003 - 14:02:00 CST