Re: quick hot backup question...

Thanks Howard

The reason for all this was I am just brushing up for an exam (finally) and the oracle tutorial I was running through said that a logfile switch and forced checkpoint should be done before a hot backup. I was pretty sure the checkpoint was done when the file was put in backup mode, but you confirmed it.

I've had this discussion with you before regarding doing a log switch after the datafiles are copied then copying the archive log generated during the backup, and in the past went to great pains writing my script to do just that. However after I "restored" a database to another location (clone) from a set of hotbackup files and applied all the archive logs to it, I realized that what I was doing was ok, but not really necessary, like you said.

End result is that I don't bother anymore, and writing the dynamic backup scripts is a whole lot easier.

"Howard J. Rogers" <dba_at_hjrdba.com> wrote in message news:a7o4ju$vfn$1_at_lust.ihug.co.nz...
> If you're doing O/S online backups, then there's no need for a preliminary
> checkpoint, because that's precisely what the 'begin backup' command
forces
> (at least for the datafiles of the tablespace involved).
>
> The one about a preliminary log switch (presumably because you are about
to
> copy the archives) is always a curious one. Lots of people do it, and
I've
> never really understood why. Usually the justification is that without
it,
> you are short of the current redo log, so you may lose data. There's
> something to that, I suppose. But it's also usually (so I find) because
> people view a backup as an isolated event, whereas the truth of the matter
> is, of course, that what you don't backup tonight you will backup
tomorrow.
> So if there's a bit of current redo left unbacked up, who cares?? You'll
> get it when tomorrow's backup is performed, and in the meantime there's no
> possible risk of data loss because you've multiplexed your online redo
logs,
> and then mirrored them with hardware RAID. Haven't you?? ;-)
>
> The other thing that mystifies me about forcing a log switch in order to
get
> an archive of the current log is that it only makes another log the
current
> log. So you can *never* really be completely and utterly up-to-date with
> redo copies, unless you stop all your users doing things: there'll always
be
> a new piece of current redo which you haven't backed up today. Hence cold
> backups, of course.
>
> That said, a log switch does no real harm -except induce a
> performance-hitting checkpoint.
>
> Regards
> HJR
> --
> ------------------------------------------
> Resources for Oracle : www.hjrdba.com
> ============================
>
> "Glen A Stromquist" <gstromquist_at_nospamyahoo.com> wrote in message
> news:jpMn8.11561$EV.366849_at_news1.telusplanet.net...
> > In my online backup scripts I don't do a logfile switch or force a
> > checkpoint before copying the datafiles.
> >
> > Is this recommended by Oracle?
> >
> > I'm wondering if I overlooked something when writing my scripts, I have
> used
> > my online backups on occasion to create a clone db, so I know they
"work"
> > the way I'm doing it now, but I guess it can't hurt to build in a
logfile
> > switch and/or force a checkpoint as part of the script as well.
> >
> > Curious to hear what others do regarding this....
> >
> >
> > cheers!
> >
> >
>
>
Received on Mon Mar 25 2002 - 16:21:25 CST