RE: CPU COSTING
- From: "Khedr, Waleed" <Waleed.Khedr@xxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 23 Apr 2004 11:28:56 -0400
So the buffer cache has no impact on the stats.=20
Was wondering how this system stats get calculated, it has to be =
collected by the individual sessions themselves and then all the =
collected numbers get summarized/correlated into one set of numbers =
(system level).
Waleed
-----Original Message-----
From: Jonathan Lewis [mailto:jonathan@xxxxxxxxxxxxxxxxxx]
Sent: Friday, April 23, 2004 10:59 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: CPU COSTING
Not quite -
The new cost model allows Oracle to work
out a better balance between the time taken
for a single and multi-block read -- which is
what people used to use o_i_c_a for.
It does not (yet) allow for the fact that the
buffer cache exists. Consequently you need
to consider opt_ind_cache still; and review
the value for o_i_c_a, view it as an indicator
of the percentage of table I/Os that will turn=20
into real physical read requests.
10g has indications that it will also consider
the recent history of per-segment cache benefits
to modify costs and plans - but I don't think it's
enabled in the current release.
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=20
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
----- Original Message -----=20
From: "Khedr, Waleed" <Waleed.Khedr@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Friday, April 23, 2004 3:25 PM
Subject: RE: CPU COSTING
So for reads (i/o0 it measures the logical reads that might get =3D
translated to physical or not. It's affected by the buffer cache, and =
=3D
this makes sense.
So as you said, any changes/tuning to oica and oic (opt_ind_cache) might =
=3D
need to be altered again.
Waleed
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