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
> > >
> > > --
> > > Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> > > --
> > > Author: Carle, William T (Bill), NBSO
> > > INET: wcarle_at_att.com
> > >
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> >--
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> >Author: Cale, Rick T (Richard)
> > INET: RICHARD.T.CALE_at_saic.com
> >
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
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> Author: Rachel Carmichael
> INET: carmichr_at_hotmail.com
>
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> San Diego, California -- Public Internet access /
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subscribing).
Gaja Krishna Vaidyanatha
Director, Storage Management Products, Quest Software Inc.
Office : (972)-304-1170, E-mail : gajav_at_yahoo.com
Author - Oracle Tuning 101 by Osborne McGraw-Hill
"Opinions and views expressed are my own and not of Quest"
Received on Wed Oct 18 2000 - 13:02:47 CDT
