RE: Rollback Segment Philosophy

  • From: Kevin Lange <klange@xxxxxxxxxx>
  • To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 20 Jul 2004 12:53:13 -0500

Is there any performance hit on the database if you add in too many segments
or too large of segments ?

The only thing I ever heard was that you waste disk space .

-----Original Message-----
From: Mercadante, Thomas F [mailto:thomas.mercadante@xxxxxxxxxxxxxxxxx]
Sent: Tuesday, July 20, 2004 12:47 PM
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: RE: Rollback Segment Philosophy


Kevin,

My philosophy about Rollback Segments is to have enough and the correct size
so that we never experience a "Snapshot too old".

Beyond that, it all comes down to implementation.  I end up sizing the
rollbacks so that 99% of the time, everything works fine.  If a job blows up
because of rollback problems, I ask the application folks to redesign it -
change the commit strategy so that it doesn't happen again.

It's all a balance between reserving (wasting) too much space in Rollback
Segments and getting the job done.  Sometimes you have to add rollback
segment space, and sometimes the applications folks need to alter the job
being run.

Hope this helps.

Tom Mercadante
Oracle Certified Professional


-----Original Message-----
From: Kevin Lange [mailto:klange@xxxxxxxxxx] 
Sent: Tuesday, July 20, 2004 1:36 PM
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: Rollback Segment Philosophy


Evening;
  Is there 'accepted' philosophy on Rollback Segments and how many and how
big they should be ?

We are running an 8.1.7.4 database on Solaris 5.9.  The database is a hybrid
Transactional with some long running processes.

We have always made it a point to have a limited number of rollback segments
using a limited amount of space.  But, the issue of no space no longer
applies.

Since we are starting to get rollback issues due to running out of space on
our rollback segments we have decided to reopen our analysis of our rollback
design.

I was just wondering if any of you would mind sharing your philosophy on
Rollbacks .

Thanks

Kevin
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