Re: clustering factor

Hard to say -

You can only change the clustering factor of an index by rebuilding the table and index.

If the clustering factor is close to the number of blocks in the table, it's good; if its close to the number of rows in the table, it's bad. It measures how well sorted the table is relative to the index. (it's irrelevant to bitmap indexes though).

A better measure of how usable the index is comes from the value 'data blocks per key', which is the number of data blocks that Oracle will, on average, visit if you query the table with an equality predicate on columns of the index. In many systems, with large tables, this actually equates to nearly the number of physical I/Os against the table that the query will cause.

--
Jonathan Lewis
http://www.jlcomp.demon.co.uk

Host to The Co-Operative Oracle Users' FAQ
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Practical Oracle 8i: Building Efficient Databases

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alainc wrote in message <9vveqv$k7g$1_at_s1.read.news.oleane.net>...


>hi,

>

>i try to understand the clustering factor but ican't

>

>i get 3000 block of index  a clustering factor of 13000 and a number of row

>of 150000. so is it good or bad and if bad what to do to increase it?

>

>thanks

>

>

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