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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Re: which should be faster
If the CBO now considers CPU costing couldn't it change the execution plan
of tuned 8i queries to decrease throughput and possibly also degrade
response time for a particular query? For example, I have a batch program I
am running in parallel and since I know I will run it without other
concurrent sessions (in a purely batch window) I am happy to use 80% of my
CPU. Now in 9i CPU cost is taken into account, the CBO uses a different
execution plan and the batch process is taking slower although throughput is
increased?
Oracle OCP DBA
-----Original Message-----
Sent: Monday, May 05, 2003 2:50 PM
To: Multiple recipients of list ORACLE-L
What I tried to say over the weekend was:
Predicate order should not matter in 9i
because you should be using CPU costing,
and Oracle 9i will re-arrange predicate ordering
to minimise CPU load, and report this fact
in the explain plan.
Predicate order CAN have an impact on
8.1.7 because Oracle 8i (and earlier) does
not consider CPU cost when working out
an execution plan.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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> jonathan lewis posted over the weekend that it does. He said it does
in 9i unless you have a certain parameter set. Cant remember what that
was off-hand.
>
> >
> > From: "AK" <oramagic_at_hotmail.com>
> > Date: 2003/05/05 Mon AM 11:46:41 EDT
> > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > Subject: Re: which should be faster
> >
> > does predicate order makes diff in cob also ?
> > oracle 8.1.7
> >
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: jonathan_at_jlcomp.demon.co.uk Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: Paula_Stankus_at_doh.state.fl.us Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Mon May 05 2003 - 14:08:21 CDT
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