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Re: undo header congestion? (8.0.5)

From: Richard Foote <richard.foote_at_bigpond.com>
Date: Wed, 28 Jan 2004 13:09:05 GMT
Message-ID: <RvORb.32341$Wa.4250@news-server.bigpond.net.au>

"Bjørn Augestad" <boa_at_metasystems.no.spam.to.me> wrote in message news:unJRb.31572$BD3.7011381_at_juliett.dax.net...
>
> Statspack indicates that 1 or 2 RBS is fine most of the time, but from
> time to time we spend a lot of time waiting for "undo header".
>
> One of the instances is a backend db server for a web site. The load
> tends to spike a lot during the day/week/year. I'd therefore rather have
> too many rollback segments than too few, even if it wastes some disk
> space. We also have issues with e.g. blocking transactions and clients
> hanging, and I want to be able to rule out RBS shortage as the cause for
> those problems.

Hi Bjørn

The little point I would make here is that although too few is certainly not recommended (and you appear to have to few at the moment if undo header waits are causing you performance issues), note that too many can be a problem as well. As well as wasting storage, it hurts performance as it's likely to increase the number of physical I/Os which is never a good thing.

You need the "right" number (and the right size), enough to not cause contention, snapshot problems, etc. during peak loads but no more.

Cheers

Richard Received on Wed Jan 28 2004 - 07:09:05 CST

Original text of this message

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