RE: 9i - ASSM
- From: "Koivu, Lisa" <Lisa.Koivu@xxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 5 Mar 2004 10:37:09 -0500
Jonathan, can you expand on the bugs you reference and how the CBO is
fooled? We have the same debate going on here.
If you have bug numbers and a nice example of the CBO choking, that
would be very helpful.
Thank you
Lisa Koivu
Orlando, FL, USA
-----Original Message-----
From: Jonathan Lewis [mailto:jonathan@xxxxxxxxxxxxxxxxxx]
Sent: Friday, March 05, 2004 3:33 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: 9i - ASSM
"Oracle features are like fine wines - they should be
allowed to mature for a few years before you try them"
(Tom Kyte - re-interpreting the commonest reason he
had heard for people avoiding new features).
On this one, my sympathies lie with your senior DBA.
1) I know that there are bugs with ASSM, and I know
that there are types of behaviour that will hit them.
2) ASSM blows the CBO's basic index cost calculations
apart, so if you don't know what's going on, you can waste
a lot of time "fixing" code that doesn't need fixing. I wonder
if this is a good reason for waiting until you go to v10 to use
ASSM - perhaps the optimizer has been clued in to the side
effects in that version.
3) ASSM is supposed to fix issues with concurrency, in
particular for RAC - but it's very hard to build and execute
proper concurrent tests; so the possibility of finding bugs in
a development environment is small. Rememebr - when you
do data loading for testing, you will have to load the data AS
IF it were coming in from real users, otherwise you're not
doing the test in a fashion that represents what's going to
happen.
On the other hand, ASSM is clearly the strategic direction
for Oracle - so at some stage you'll have to go with the flow.
You could compromise - by testing in production - design
you tablespace strategy with a view to being able to move
objects from freelist to assm (and back again) with minimum
pain, a few at a time.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
March 2004 Hotsos Symposium - The Burden of Proof
Dynamic Sampling - an investigation
March 2004 Charlotte OUG (www.cltoug.org) CBO Tutorial
April 2004 Iceland
June 2004 UK - Optimising Oracle Seminar
----- Original Message -----
From: "Mark Moynahan" <Mark.Moynahan@xxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Thursday, March 04, 2004 9:49 PM
Subject: 9i - ASSM
: We are having a debate on building tablespaces with automatic segment
space
: management (ASSM). This is a 9i db on a Solaris box. I'm in favor of
using
: ASSM but the senior dba is a bit hesitant and want to put in manual
mode.
: I've even tried to persuade him with the Oracle documentation but he
insists
: its not mature enough for production.
:
: Is there any white papers or matalink papers that show the pros and
cons
to
: ASSM in 9i? Has anyone had issues with using ASSM? Is there a way of
proving
: ASSM is better than MSSM?
:
: Thanks,
:
: Mark
:
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