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Home -> Community -> Mailing Lists -> Oracle-L -> Re: CPU COSTING
You collect statistics for a "typical" period.
(Session 10 - slide 14 of Optimising Oracle)
Simplest option:
execute dbms_stats.gather_system_stats('start')
twiddle thumbs for a while
execute dbms_stats.gather_system_stats('stop')
You can set sql_trace true to see what actually happens.
The idea is that you want Oracle to optimise the SQL for a given machine load - and the machine load is represented by the relative I/O speeds, and the apparent CPU speed.
Lapsing into economics - the old CBO worked on the Adam Smith principle .. every does the best they can and the market makes things stabilise; the new CBO works on the John Nash equilibrium .. if everyone knows what everyone else is doing, then there is a point at which not unilateral change can improve the net benefit.
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
April 2004 Iceland http://www.index.is/oracleday.php June 2004 UK - Optimising Oracle Seminar July 2004 USA West Coast, Optimising Oracle Seminar August 2004 Charlotte NC, Optimising Oracle Seminar September 2004 USA East Coast, Optimising Oracle Seminar September2004 UK - Optimising Oracle Seminar
I was talking about how it gets populated, or the processes involved in = calculating the numbers there. if the numbers are already in v$filestat, = why do I have to collect it?
Regards,
Waleed
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