Re: Why is on-line backup one tablespace a time?

Cut to the chase.

File 1 gets backed up when its sequence number is 17001. File 2 when its sequence number is 18003, File 3 when its sequence number is 19003, and file 4 when its sequence number is 20005.

All archives are available since time 17001, and the current redo log is multiplexed and is thus safe and sound.

The current database sequence number is 23456.

File 3 blows up. You restore it. SMON, at startup notices that 19003 doesn't agree with the controlfile & other files at 23456. It will prompt for recovery -ie, the application of the transactions related to sequence 19004. Can you supply it? Yes -it's in the archive logs. Can you supply 19006? Yup. 19907? Yup. And so on. And as those transactions are re-applied to file 3, so it gets closer and closer to time 23456.

There comes a point where file 3 IS at time 23456. Media Recovery Complete, Alter Database Open.

This is reasonably basic stuff. You need to read up on it. Please see http://www.geocities.com/howardjr2000, and navigate to Courses, Backup and Recovery, and download the 70 page document I posted there.

Regards
HJR "Dino Hsu" <dino1_nospam_at_ms1.hinet.net> wrote in message news:deljot0t5or59m9ke6ph136iq9qh7j17hl_at_4ax.com...
> On Sun, 26 Aug 2001 22:32:45 -0700, "Sean Fitzgerald"
> <sfitzgerald_at_centurytel.net> wrote:
>
> >> Do you mean that the backup of datafiles + online redo logs will do
> >> for recovery even there are time-difference among the backed-up
> >> tablespaces?
> >
> >You don't back up online redo logs. If you did and you restored them you
> >would lose any transactions in the current logs. This is why you need to
> >have multiple members in each redo group and have your disk drives
mirrored.
> >You don't want to lose your online logs.
> >
> > In terms of transaction management or SCNs, please
> >> explain why this is recoverable?
> >
> >This is the basics of any recovery. An old file is restored and the
> >archived logs + online logs bring the datafile back to the current SCN.
>
> OK, I see that archived logs and online logs are secured by
> multiplexity, not by backup. I still don't understand why these
> tablespaces can be backed up at different times.
>
> Let's say data1.ora, data2.ora, data3.ora are three datafiles and
> belong to ts1, ts2, ts3 tablespaces, on-line backup are performed at
> t1, t2, t3 when SCNs are n1, n2, n3. t1<t2<t3, thus n1<n2<n3. Now that
> the instance fails (say t4), I copy datafiles back to where they were,
> and start the instance with the current (t4) controlfile, archived
> logs, and online logs, Oracle will be brought back to the state of t4?
>
> >snip
>
> Dino
>
Received on Mon Aug 27 2001 - 05:35:00 CDT