--
"quarkman" <quarkman_at_myrealbox.com> wrote in message
news:oprtnqk2wfzkogxn_at_haydn...
> On Sat, 9 Aug 2003 12:39:31 -0500, Burton Peltier
> <burttemp1REMOVE_THIS_at_bellsouth.net> wrote:
>
> > "Anton Buijs" <remove_aammbuijs_at_xs4all.nl> wrote in message
> > news:3f3510b5$0$49108$e4fe514c_at_news.xs4all.nl...
>
> >
> > This is the main reason where you would need the REDO logs. I thought
> > that
> > was what I said? After re-reading my post, it IS what I said.
> >
> > Just to be clear... I did not mean to imply and I know you do NOT
recover
> > REDO logs when recovering from a hot backup. The entire context of the
> > OP
> > was a problem with a cold backup. All of the comments in my post were
> > about
> > cold backups ONLY.
> >
> > Hot backups are different, of course.
>
>
> The temperature of your backups makes no difference. You should never
> backup online redo logs, period. Archivelog or noarchivelog, hot or cold.
>
> The subtler point is that's it's fine to do cold backups, even in
> archivelog mode. Indeed, cold backups with archivelog mode is quite
> possibily the nicest combination of options available to the dba. But
> herein lies the source of possible confusion: I'm in archivelog mode, I
> take cold backups... is it therefore OK for me to backup my online redo
> logs? No it isn't, because I risk data loss at the time of restore.
I suppose I am missing something here still... please explain....
If there is some strange occurence in your cold backup "clean shutdown" and
you don't have REDO logs, don't you take a risk with open resetlogs?
And, in the above scenario, what does the archivelog or noarchivelog have to
do with it?
Note: We usually run in archivelog mode for prod and test and do cold, hot,
and export backups . I think I am covered :) hopefully I am (don't want ot
jinx myself).
>
> So some cold backups, it would be OK to back them up (noarchivelog ones)
> and some it wouldn't (archivelog ones). Not very consistent advice, is it?
> For newbies, I mean.
>
> >
> > Anyway, it sounded like a real possibility (needing the REDO logs or
> > having
> > to do a reset logs) for this person who is doing a cold/offline backup
> > and
> > does a shutdown abort every now and then because the immediate isn't
> > coming
> > back soon enough.
> >
> > I would add for the OP... if this is occuring often, I would look into
> > what
> > is running at the time you are attempting a cold backup. Someone
probably
> > has a job that is kicking off at the same time or right before and you
> > could
> > get them to change the start time.
> >
> > Note: I have had problems before trying to get a "clean shutdown" such
> > as:
> >
> > (1) Some job or snapshot would kick off in the middle of my "clean
> > startup/shutdown" even with the listener shutdown. So, then I would need
> > a
> > second init.ora with jobs = 0 and have to do the "clean
startup/shutdown"
> > using a different init.ora .
> >
> > (2) The "crash recovery" step would take a lot longer than you would
like
> > when doing the "clean startup/shutdown".
> >
> > So, can someone/quarkman? please explain to me what is the problem /
> > disadvantage of recovering the REDO logs, IF recovering from COLD
> > backup
> > (even if a shutdown abort was not issued).
> >
> > Seems cleaner to me to recover the cold backup with REDO logs than to do
> > a
> > reset logs command or having a potential problem getting a "clean
> > shutdown".
> >
>
>
> I don't know why suddenly 'resetlogs' is considered so evil! You would
have
> to type 'recover database until cancel'...'cancel'...'alter database open
> resetlogs'. I make that a massive 9 words of typing!
>
> Why backup something which you can never safely restore in archivelog
mode?
>
> And why make your noarchivelog cold backup backup something (possibly
> taking many extra minutes to do so, depending on their size) which you
> would then have to expend more minutes restoring... when the alternative
> re-creates them in a blink of an eye? I dispute the reasoning that a full
> restore would be quicker than an open resetlogs, particularly if you're
> restoring from tape.
None of our REDO logs are more than 100Meg ... x 4 x 2 = 800Meg. We backup
to disk and typically get about a 20 Meg per second transfer rate. So, it
would take me something like 40 seconds to restore all the logs and their
multi-plex copy.
>
> But the real issue is as I mentioned earlier: backing up the redo logs is
> only feasible when you are in noarchivelog mode. The advice not to back
> them up, ever, works 100% of the time, regardless of the nature of your
> database.
>
> ~QM
Received on Sat Aug 09 2003 - 19:20:07 CDT
