Re: clustering factor

The clustering factor is a measure of how well sorted the data is in relation to the index. Size is relative - if the data is perfectly sorted for the index, the clustering factor should match the number of blocks in the table, if the data is extremely randomly distributed w.r.t the index then the clustering factor will be similar to the number of rows in the table.

For 12M rows, a clustering factor of 1M sounds a little large (unless the rows are so large that you have only 12 rows per block).

Note: the above comments do not apply to bitmap indexes which always have a very
small clustering factor. The numbers may also be distorted in 8.1 by compressed,
reverse key or function based indexes.

--
Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Practical Oracle 8i:  Building Efficient Databases

Publishers:  Addison-Wesley
Book bound date: 8th Dec 2000
See a first review at:
http://www.ixora.com.au/resources/index.htm#practical_8i
More reviews at: http://www.jlcomp.demon.co.uk/book_rev.html



thuge wrote in message <9110rr$1g3$1_at_nnrp1.deja.com>...


>

>

>I use Oracle 8.0.6 with SAP R/3. I have a lot of indexes with big

>values for "clustering factor" (998745 for an index of about 12 million

>rows). I remember i've read something on this item and it has something

>to do with performance.

>I don't remember what this means and i've never found further

>explaination on it since this moment.

>Could someone explain

>1. what it has to do with performance problem (if it has) ?

>2. what is bad ? a big number or a little one ?

>3. How can i solve it ?

>

>Regards,

>

>--

>Thierry HUGE

>AIX/Oracle/SAP Administrator

>STEELCASE STRAFOR (FRANCE)

>

>

>Sent via Deja.com http://www.deja.com/

>Before you buy.