Re: Rollback Segment Question

From: A. Bardeen <abardeen1_at_yahoo.com>
Date: Tue, 31 Jul 2001 05:02:52 -0700
Message-ID: <F001.00359CCF.20010731035551@fatcity.com>

Kamel,

Just because an RBS can extend doesn't mean it will.
>From the description you've given I suspect that the
transactions were committing fast enough that when it came time to wrap around from one exent to the next, the next extent didn't have any active transactions so it was reused without having to extend. By setting minextents to 100, you forced the RBS not to wrap around and reuse extent 1 until it had filled up all 100 extents. Checking WRAPS in V$ROLLSTAT will show the number of times the RBS has wrapped.

BTW, the studies done back on Oracle7, or perhaps even earlier, found a minextents of 20 to be the best setting on average.  

HTH,

• Anita
  • GL2Z/ INF DBA BENLATRECHE <kbenlatreche_at_lth.sonatrach.dz> wrote:
    > Hi All
    >
    > I had a long PL/SQL prg to run .
    >
    > I created a special rollback segment for that
    > script with the storage of
    > (initial 1 m next 1m minextents 2).
    >
    > After a few minutes of running I got the "Snapshot
    > too old" error.
    >
    > In the v_$rollstat view I got : extents=2, rssize
    > ~ 2 M, hwmsize ~ 2 M.
    >
    > I recreated the RBS with minextents 100, at this
    > time my program run
    > succefully.
    >
    > My question is why in the first case the RBS didn't
    > growth automatically by
    > allocating a new extents until maxetents value ?
    >
    >
    > Thank you
    >
    > Best Regards
    > Kamel Benlatreche
    

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Author: A. Bardeen
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Received on Tue Jul 31 2001 - 07:02:52 CDT