Re: oica/oic
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 19 Apr 2004 19:21:16 +0100
db file sequential read comes from single block
reads, which tend to be indexed accesses anyway.
Both these parameters make the optimizer reduce
the "calculated cost" of a single block reads - not
the "actual resource requirement" - which tends to
favour indexed accesses over tablescans, and can
favour bad indexes over good indexes.
Consequently, if you are already seeing a lot of
db file sequential reads, fiddling with these parameters
is not very likely to help.
Your best bet is to examine sessions (such as your
batch job) which are exhibiting excessive wait time
on these reads, then focus on the SQL that is used
by those sessions to figure out why particular statements
are doing excessive amounts of reads. Once you know
what the problem is, you have a better chance of picking
an appropriate solution.
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
----- Original Message -----
From: "Raghu Kota (WBTQ)" <RKota@xxxxxxxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Monday, April 19, 2004 5:51 PM
Subject: RE: oica/oic
Thankyou Jonathan! I read that document, I don't know exactly what Iam =
missing!! But last two months Iam checking my db with lots of db file =
sequential reads(90%) in my statspack, so lots of single block reads and =
multiblock reads with nested loops. Most of my erp tables had indexes =
with stats. So optimizer has same info to make better decision??
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