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Re: TRANSACTIONS_PER_ROLLBACK_SEGMENT (the real story)

From: <markp7832_at_my-deja.com>
Date: Tue, 04 Jan 2000 15:06:55 GMT
Message-ID: <84t2a3$5v1$1@nnrp1.deja.com>


In article <89o37skkj9a3pqs4gu3ujkbeh0i93dqhpv_at_4ax.com>,   john v <johnvue_at_gte.net> wrote:
> On Tue, 4 Jan 2000 08:00:48 +0100, "Sybrand Bakker"
> <postmaster_at_sybrandb.demon.nl> wrote:
>
> >The real story may be higly misleading...
> >
> >If you have public rollback segments this parameter will determine
(based on
> >the number of processes in init<sid>.ora) how many rollback segments
are
> >brought online.
> >This is, AFAIK, a one-time operation, rollback segments are not added
> >dynamically.
> >Hundred segments is outrageous. Oracle has the 'rule of four' which
means
> >one rollback segment for every four users, with a minumum of four
rollback
> >segments.
> >
>
> I have over 600+ users ... which mathematically works out to 150
> rollback segments. I really didn't need that many so I cut it down to
> 100.
>
> I've never been a big fan of the "divide by four" rule -- I'd rather
> go by # of simultaneous transactions at peak times.
>

Having 100 rbs segments is excessive. If I remember correctly the Oracle ver 7 documentation specifically mentions not exceeding a certain number which I think is around 44. I do not remember a limit being listed in the ver 8 manual but I suspect that it would be the same.

You should determine your number of rbs segments from your number of simultaneous transactions like you mentioned. Select count(*) from v$transaction several times during peak hours. I bet that your counts will be well below 44, much less 100, and since an rbs segment can handle multiple transactions at a time you should probably consider reducing your number of rbs segments and making your remaining segments bigger since I expect that with 100 of them that they are pretty small.

Just my opinion.

--
Mark D. Powell -- The only advice that counts is the advice that  you follow so follow your own advice --

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Before you buy. Received on Tue Jan 04 2000 - 09:06:55 CST

Original text of this message

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