Re: Do I really need more than 1 rollback segment?

We could have a battle of the giants on our hand here. Steve Adams says make 'em big, and who cares about a bit of wasted space: these things are supposed to be on their own hard disk anyway. (I am paraphrasing like crazy, natch).

Personally, I go for the Steve Adams school of thought on this one. I can't see any drawbacks (though I'm sure Jonathan will elaborate on the 'additional I/O' idea) of large segments. It's the NUMBER of them that's the worry, to avoid contention issues.

As for sizing them "appropriately" -you must have the best behaving set of Users I've never met. It takes just one of them to raise a transaction and leave it uncommitted, and growth will follow as sure as day follows night. The more "appropriate" your segments are for daily use, the more such growth will be required in such circumstances. And that's the reason I *still* wouldn't touch optimal with a bargepole.

Regards
HJR

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Resources for Oracle: http://www.hjrdba.com
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"andrew_webby at hotmail" <andrew_webby_at_hotmail.com> wrote in message
news:f45d9b0.0112110438.414536d_at_posting.google.com...


> Just as a 'further', I knew I'd picked up that "rule of thumb"

> somewhere and as in my previous post, it was when I posted my

> statspack report some time back.

>

> From Johnathan Lewis:

>

> "As already appreciate, your rollback segments

> seem to be much too big for activity shown, and

> the optimal is too high -  little known rule of thumb,

> rollback segments should be as small and as few

> as possible to reduce redundant I/O.  In your case

> the size of the rollbacks doesn't seem to have

> resulted in any significant I/O cost."

>

> I'm sure his meaning was not to set them incredibly small as I

> appeared to be suggesting, but more to size them appropriately.

> Comments appreciated.

>

> Andrew

>

> "Howard J. Rogers" <dba_at_hjrdba.com> wrote in message

news:<3c110a2a$0$29051$afc38c87_at_news.optusnet.com.au>...


> > I agree with your disagree!  Setting rollback segments 'as small as you

can


> > make them' is just plain daft, and setting optimal at all is equally

mad.


> > Optimal is there for those databases that don't have a full-time DBA,

and as


> > such it can be a useful 'light-weight management' tool.  But in a

> > properly-managed production database, it's an utterly lousy idea.

> >

> > Regards

> > HJR

> > --

> > Resources for Oracle: http://www.hjrdba.com

> > ===============================