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Re: how to set optimizer_index_cost_adj and cache parameters?

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Fri, 26 Mar 2004 18:21:50 -0000
Message-ID: <002501c4135f$360e6370$7102a8c0@Primary>

Waleed

Thanks for the note. You're absolutely right,

I sent in a note to the editor just before publication because I had missed out the phrase "of the clustering factor" completely; unfortunately my explanation of where to put it wasn't quite clear enough.

I'll send her a correction a.s.a.p

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

Hi Jonathan,

This is from the article:
"Essentially, this formula tells Oracle the number of block visits (see side bar) that a process will have to make to collect all the data from the table. If the selectivity (fraction of the table's data) is X, then it seems reasonable that the number of index leaf blocks to visit will be X% of the clustering_factor; and the number of table block visits will also be X%. Add on the fact that you have to walk from the root to the leaf level just once, and you have the formula."

I believe it's the other way around:

the number of index leaf blocks = X% of leaf blocks the number of table block visits = X% of clustering_factor

Regards,

Waleed



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Received on Fri Mar 26 2004 - 12:18:17 CST

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