RE: RAC and FREELISTS/FREELISTGROUPS
- From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>
- To: "Jed_Walker@xxxxxxxxxxxxxxxxx" <Jed_Walker@xxxxxxxxxxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 4 Oct 2011 17:36:21 -0400
Jed,
Are you really doing dictionary managed? I'm a bit fried, here at OOW, but, if
my brain is firing on all cylinders, you can do FREELISTS/FREELIST GROUPS with
locally managed tablespaces. It's ASSM (Automatic Space Segment Management)
you need to stay away from if you want to be able to configure
FREELISTS/FREELIST GROUPS.
So, if you're really on dictionary managed, you should definitely move to
locally managed.
As to ASSM vs. MSSM, Jonathan Lewis looked into this when the feature was first
introduced, (10g, I think?) and concluded that ASSM is effectively equivalent
to 16 FREELISTS, in terms of concurrency. I'm not aware of any changes to that
for 11g. You might want to check his blog. Also, if I bump into him, I'll ask
him to check his email when he has a chance, and weigh in on this thread.
Hope that helps,
-Mark
________________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] On Behalf
Of Walker, Jed S [Jed_Walker@xxxxxxxxxxxxxxxxx]
Sent: Tuesday, October 04, 2011 14:16
To: oracle-l@xxxxxxxxxxxxx
Subject: RAC and FREELISTS/FREELISTGROUPS
We have a 10.2.0.4.0 RAC database that I'm currently building a new 11.2.0.3.0
RAC for. We will migrate to it one schema at a time using Data Pump.
The current database has dictionary managed tablespaces that were created so
that some objects could be created using FREELISTS and FREELISTGROUPS to
resolve performance issues. Exact knowledge of what those were doesn't exist
anymore; however, I believe it is related to notes I've seen regarding "high
DML tables and a tradeoff between buffer busy waits and DML contention". From
what I'm reading 11gR2 has done a lot to fix this issue, and unfortunately we
don't have an environment to truly test beforehand.
Any knowledge and advice would be greatly appreciated.
- Jed
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