Re: A question on data conformity during hot backup

On Thu, 22 Oct 1998, You Dunhua wrote:
>
> Oracle provides mechanism for hot-backup the tablespace. But suppose I
> have transactions happening on two tablespaces at the same time, how I
> can keep the conformity between the them? I mean, first I backup one
> tablespace online, then backup the other one, surely they correponds to
> two different time stamps. How can I solve the problem? It must be a
> stupid question. Thanks for helping me out.

You are right that a hot backup takes an inconsistent backup of the datafiles. In fact they are not only inconsistent with each other, but even inconsistent within a given file, since the database continues to write the file during hot backup.

Everything gets synched back up when you go to recover the database. You apply archived redologs through the point in time that the backup finished, and even beyond that to any point in time that you want. By applying logs, all the datafiles get synched back up.

BTW, we had quite a go-around recently on the very topic of hot backup internals. If you are interested, you can view the thread on DejaNews:

http://www.dejanews.com/dnquery.xp?search=thread&recnum=%3cPine.OSF.3.95.980923214703.10554A-100000@gonzo.wolfenet.com%3e%231/1&svcclass=dnserver

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Jeremiah Wilton http://www.wolfenet.com/~jeremiah Received on Thu Oct 22 1998 - 12:02:04 CDT