Re: how to set optimizer_index_cost_adj and cache parameters?

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 25 Mar 2004 16:51:27 -0000
Message-ID: <01c001c41289$6ca24590$7102a8c0@Primary>

Just in case you haven't come across it, the following article of mine has just been published on DBAZine:

www.dbazine.com/jlewis18.shtml

OICA is a bit of a threat because it's often treated as a standalone solution, when it's really part of a strategy for getting the truth into the optimizer.

It's also a bit of a bodge job in 8.1 anyway, because it tries to fix two issues simultaneously (caching and relative read speeds). It is also easy to set it to an inappropriate value because of the impact that bad SQL can have on your attempts to work out a reasonable value.

Just to add to the confusion - whatever you do in 8.1 should be reconsidered for 9.2 anyway, where system statistics can be used to set relative I/O speeds and OICA can be used as an indicator of caching benefits on tables.

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

Original Message ----- From: "Juan Cachito Reyes Pacheco" <jreyes_at_dazasoftware.com> To: <oracle-l_at_freelists.org> Sent: Thursday, March 25, 2004 1:23 PM Subject: how to set optimizer_index_cost_adj and cache parameters?

: Hi,
:
: After reading a lot about this, this is my conclusion, do you agree?
:
: the conclusion seems to be gather system statics from every distinct
process
: or group of process, and set manually this values in every one of them.
:
: If this process is by time, for example night and day, you can use alter
: system parameter,
: if this is only for ap articular process you will have to set alter
session.
:
: And set the value.
: This seems to be a hard work.
:
: regards,
:

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Received on Thu Mar 25 2004 - 11:04:08 CST