Re: Oracle 8i (8.1.7.0.1) + Redhat Linux 7.2 = Cannot create tablespace file > 2 gb

"Sean M" <smckeown_at_earthlink.net> wrote in message news:3D1D5C0E.C959353A_at_earthlink.net...
> "Howard J. Rogers" wrote:
> >
> > "Sean M" <smckeown_at_earthlink.net> wrote ...
> >
> > > In practice, most incomplete recoveries of production databases roll
> > > back to a point in time earlier than the data contained in the online
> > > redos. That's been my experience, and I bet most others' that do this
> > > on real production systems. Why? Because most real production
systems
> > > switch logs rather frequently (say, a few times per hour),
> >
> > I hope not. But perhaps things are different south of the equator. Most
DBAs
> > I know of here would switch every hour or so. And I disapprove (since
they
> > are only protecting themselves against Instance failure by doing so, and
I
> > happen to think that hardware and most O/Ses, not to mention UPSes have
> > gotten to the point where I hope we can start to stop worrying about
> > instance failures).
>
> [What the hell, more thread drift...]
>
> I'd postulate at least 2 other reasons for more frequent log switches
> than once a day. First, for many of our databases (and in many other
> large shops out there), we generate 50-200 GB of redo a day. Making
> 50-200 GB online redo logs really isn't very practical for backup and
> recovery, for many of the same reasons we've seen in this thread for not
> using large datafiles (i.e. higher granularity of the recovery process
> is usually beneficial). Secondly, even if we did only switch once a day
> for these databases, that would incur one BIG checkpoint (by big I mean
> a LOT of dirty buffers being written to datafiles, all at once). That
> means once a day we get a HUGE performance spike, as opposed to many
> smaller spikes (a few times per hour). For 24/7 systems, we can't
> really tell our users that everything runs great except for that one
> 45-minute period where you can't do a darn thing because, sorry, we're
> checkpointing. But we can tell them that everything runs pretty well
> all day long.

Drift on by.....

Well, here comes a statement. True 24x7s are very rare. There's usually/frequently/often a sluggish window. And yes, I'd be aiming to get my log switches into there.

File sizes... can't do anything about them, agreed. But I always try and create 2Gb redo logs and have done with it.

Unless they don't have redundant power supplies and a UPS.

And if they're running on NT 4.0, forget it. Every 20 minutes or so in that case!

> And I wouldn't understate the frequency of instance crashes. If they
> weren't still a problem with modern hardware we wouldn't see such an
> interest in RAC.

(Psst. Between you and me, we see a lot of interest in RAC because Oracle wants it that way. All hail the marketing department. Call me a cynic, if you must).

Rgds
HJR
>Bugs, hung processes, memory leaks, cpu failures, you
> name it - instance failure isn't going away anytime soon. I think
> you're once-a-day switch idea will be a hard sell in production, but
> don't let me stop you. :)
>
> Regards,
> Sean
Received on Sat Jun 29 2002 - 02:25:16 CDT