Re: Question in HOT BACKUP

On Sat, 2 Oct 2004, Chirag DBA wrote:

> When I was asked which filese I will copy for hot backup, I said redo too.
>
> Cause I think they can help us always to recover database upto point of time.
>
> I was pulled a lot, but my only question that if not redo then how
> will you recover yr DB upto point of failure, stopped the arguements.

Askdba removed from the distribution.

If you can win the argument, you must be right! Anyway good for you for checking on this even though you convinced the interviewers you were right.

The reason that many people recommend against backing up online logs during hot/cold backup is twofold:

1. If you back up the current online log, you have no guarantee of obtaining a clean copy since log writer might be halfway through performing a write. You should obtain the most recent log by archiving it (archive log current).
2. If you restore a backup including the online logs (in their normal location) and the controlfile is also restored in the normal location, then the restored database can be brought up in such a way that crash recovery would take place automatically without prompts, and there could be no opportunity to apply archive logs to roll the database forward to a future point in time.

It is likely that you might want to recover past the point in time of the backup, thus the online logs would be nowhere near the most current logs for the purposes of a restore/recover exercise.

--
Jeremiah Wilton
http://www.speakeasy.net/~jwilton
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