RE: Rollback Segment Shrinkage Question

Note that to determine the value for optimal: value of initial extent * value for minextents

The minimum value for minextents should be 20. By default it is 2.

G!
--- Gaja Krishna Vaidyanatha <gajav_at_yahoo.com> wrote:
> Hi Rachel,
>
> Just to add another point to what you have mentioned
> here, and
> that is the increased probability of 'ORA-1555
> snapshot too old'
> occuring when OPTIMAL clause is set too low in the
> rollback
> segments. This is especially true when your
> environment
> supports a large number of small transactions and
> some long
> running reports.
>
> Cheers,
>
> Gaja
>
> --- Rachel Carmichael <carmichr_at_hotmail.com> wrote:
> > nope, it doesn't. Oracle only checks the size of
> the rollback
> > against
> > optimal when you need to move from one extent
> within the
> > rollback segment to
> > another.
> >
> > You are right that when it shrinks automatically
> it can have a
> > performance
> > hit but that's usually minimal. What's important
> to check is
> > to see if your
> > rollback segments are extending and shrinking
> constantly. If
> > they are, you
> > have sized them and/or the optimal parameter
> incorrectly.
> >
> >
> > >From: "Cale, Rick T (Richard)"
> <RICHARD.T.CALE_at_saic.com>
> > >Reply-To: ORACLE-L_at_fatcity.com
> > >To: Multiple recipients of list ORACLE-L
> > <ORACLE-L_at_fatcity.com>
> > >Subject: RE: Rollback Segment Shrinkage Question
> > >Date: Tue, 17 Oct 2000 08:25:54 -0800
> > >
> > >I think after the transaction completes it will
> shrink back
> > to optimal.
> > >Keep
> > >in mind their is a performance
> > >hit and you should monitor the frequency of
> dynamic
> > extensions.
> > >
> > >Rick
> > >
> > > > -----Original Message-----
> > > > From: Carle, William T (Bill), NBSO
> [SMTP:wcarle_at_att.com]
> > > > Sent: Tuesday, October 17, 2000 10:21 AM
> > > > To: Multiple recipients of list ORACLE-L
> > > > Subject: Rollback Segment Shrinkage Question
> > > >
> > > > Hi,
> > > >
> > > > At what point in time does a rollback
> segment shrink
> > back to its
> > > > optimal
> > > > value?
> > > >
> > > >
> > > > Bill Carle
> > > > AT&T
> > > > Database Administrator
> > > > 816-995-3922
> > > > wcarle_at_att.com
> > > >