Re: Online backup: Backup online redologs?

Howard J. Rogers wrote:
>
> Yup, absolutely. The training stuff only advises doing the Control File and
> Redo Log copies before an incomplete recovery (on the grounds that you can't
> repeat the recovery if it fails unless you do), but frankly I think anyone
> who doesn't do it as a reflex before *any* sort of recovery is as mad as a
> hatter, and deserves everything they get.
>
> Regards
> HJR
> --
> =============================!!=============================
> The views expressed are my own only, and definitely NOT those of Oracle
> Corporation
> =============================!!=============================
>
> "Nuno Souto" <nsouto_at_nsw.bigpond.net.au.nospam> wrote in message
> news:3afdea95.3495993_at_news-server...
> > On Sun, 13 May 2001 00:04:47 +1000, "Howard J. Rogers"
> > <howardjr_at_www.com> wrote:
> >
> > >
> > >Worse. Suppose you manage to get a cleanish copy of the current redo
 log.
> > >Your database then blows up, because datafile 6 is corrupted. Now you
 tell
> > >Junior DBA to deal with it, because you have a major pizza to deal with.
> > >So he restores the lot: controlfile.bkp, datafiles.bkp and redologs.bkp.
> > >They were, after all, in your backup set ...and only having gone on the
> > >Introduction to SQL Course in Sydney, what did he know about restores??
> > >
> > >Guess what? The current redo log on the corrupted system WAS fine. It
> > >could have supplied important information. It's just been over-written
 by a
> > >copy taken ten hours ago. Every other log is fine (because every other
 log
> > >has been archived). But not the current log. The current log is toast,
 and
> > >has been replaced by very stale, hours old, toast. Net result: you've
 just
> > >lost committed transactions when there was absolutely no reason for you
 to
> > >have.
> >
> > That's the most important point, I'd dare say. The fact that on
> > restore, he could be throwing away the active redo log, replacing it
> > with an old copy. Not that he'd do it, but a junior DBA or a sysadmin
> > who wasn't aware could mess it up easy. Never underestimate the power
> > of the newbie to stuff things up. I know, I was a newbie too.
> >
> > (Still am when it comes to 9i and certain aspects of 8i. We all are.
> > That's why it's important to stay actual and keep studying.)
> >
> > Going back a few years when I was taking care of a V6 database that
> > regularly needed recovery (don't ask!!!...), we got to the point where
> > we'd backup the CURRENT set of redos and control files before starting
> > the recovery, just in case we messed up the recovery steps somehow!
> > That way we had assurance we could re-start the recovery. It's that
> > important.
> >
> > In fact, I'd go as far as to say even nowadays, *BEFORE* I started
> > recovery on a corrupt database I'd make darn sure I had a copy "as is"
> > of the current control file and redo logs. They are essential if the
> > recovery messes up and you need to get into serious "dirk the daring"
> > territory to get things back.
> >
> > Cheers
> > Nuno Souto
> > nsouto_at_bigpond.net.au.nospam
> > http://www.users.bigpond.net.au/the_Den/index.html

Its one thing that Oracle should have in the manuals (imo). That before you attempt any kind of restore, you take a backup of what you've currently got...

-- 
===========================================
Connor McDonald
http://www.oracledba.co.uk (mirrored at
http://www.oradba.freeserve.co.uk)

"Some days you're the pigeon, some days you're the statue"