Re: Question on Incomplete Media Recovery

satarnag_at_hotmail.com (Rozz Williams) wrote in message news:<bc356f74.0410180949.44faddc_at_posting.google.com>...
> "Howard J. Rogers" <hjr_at_dizwell.com> wrote in message news:<4172c899$0$10345$afc38c87_at_news.optusnet.com.au>...
> > Rozz Williams wrote:
> >
> > > Hi,
> > >
> > > Here is my scenario:
> > >
> > > Disk A: Windows 2000 OS, Oracle install binaries, One controlfile
> > > Disk B: All database datafiles, online redo logs, archived redo logs,
> > > a copy of a controlfile.
> > >
> > > The database is in ARCHIVELOG mode. A Hotbackup is taken every day.
> > >
> > > Now, let's say Disk B crashes and I replace the Disk and restore from
> > > the previous day's hot backup. What do I need to do with the
> > > controlfiles to recover? Do I recover the database with "recover
> > > database until cancel using backup controlfile" or just "recover
> > > database until cancel"?
> >
> > Answer your own question: do you have a backup control file? Or do you have
> > a surviving copy of your real, live controlfile on disk A?
>
> I will have both. The controlfile on Disk A is a surviving copy
> containing current information. The controlfile on B will be a
> restored copy from yesturday's backup.
>
> > More technically, would the checkpoint change number in the control file, be
> > ahead of, or the same as, the checkpoint change number in the data files?
>
> Controlfile on Disk A will be ahead. I believe controlfile on Disk B
> will also be ahead because the controlfile is backed up after all the
> datafiles and a log switch.
>
> > > I'm thinking the following:
> > > 1. delete the newly restored control file on Disk B
> > > 2. Copy the controlfile from Disk A to Disk B
> > > 3. startup mount
> > > 4. recover database until cancel
> > > 5. issue a "cancel" (because I do not have any archived redo logs from
> > > the last backup to the point of failure)
> > > 6. alter database open resetlogs
> > >
> > > Please let me know if I am on the right track.
> >
> > Your six points seem to me entirely correct.
>
> I was also thinking of the following:
>
> 1. delete the control file on Disk A
> 2. Copy the newly restored controlfile from Disk B to Disk A
> 3. startup mount
> 4. recover database until cancel using backup controlfile
> 5. issue a "cancel" (because I do not have any archived redo logs from
> the last backup to the point of failure)
> 6. alter database open resetlogs
>
> > I would want to know why a multiplexed member of your redo logs isn't on
> > disk A, as well, though.
>
> I honestly don't like the setup myself, but as a consultant, I am not
> able to make any changes (because of all the change controls in
> place), just document what is there.
>
> If it makes you feel better, Disk B is actually a bunch of drives
> running RAID 5. I just called it Disk B for simplicity sake. I am
> actually trying to document an incomplete media recovery if more than
> one drive fails on the RAID unit. The only reason why this will be an
> incomplete recovery is because the archived redo logs are residing on
> the RAID unit.
>
> Thanks for your help, it is greatly appreciated.
>
> Regards...

Hi,

Howard is completely right. But I just wonder how you can do the incomplete recovery without some archived logfiles. Let's say you have several tablespaces and it takes 1-2 hours to complete backup for the first one. During that time some logfiles are generated. And the same thing happens to the second tablespace and so on. How can you make your datafiles in the hot backup synchronized without logfiles? Received on Mon Oct 18 2004 - 18:41:25 CDT