Re: Clustering factor smaller than table blocks.

Are the values for the indexed column are sequential values? CF depends on how the values organized in bloks of this column.

On 9/27/06, Polarski, Bernard <Bernard.Polarski_at_atosorigin.com> wrote:
>
>
>
> I have a table with 368 blocks, no free blocks, and the clustering factor of
> the primary key is 345. how is it possible?
>
> I thought that CF will give you the amount of table blocks that an index
> will need to access for a given rowset. Something like
>
> smallest( table blocks, ceil( (CF/tot table rows)*rowset/avg rows per
> block)) (real formula must be much complicated.
>
> However if I have an avg ro
>
> Here are the brute facts:
>
> select EMPTY_BLOCKS,AVG_SPACE_FREELIST_BLOCKS
> ,NUM_FREELIST_BLOCKS
> from dba_tables where table_name = 'CUSTOMERS' and owner = 'SOE' ;
>
> EMPTY_BLOCKS AVG_SPACE_FREELIST_BLOCKS NUM_FREELIST_BLOCKS
> ------------ ------------------------- -------------------
> 0 0 0
>
>
> The table was analysed with dbms_stat, percent = 100:
>
> exec dbms_stats.gather_table_stats( ownname=>'SOE', tabname=> 'CUSTOMERS',
> Degree=> 4, estimate_percent=> 100, granularity=>'ALL', cascade=>TRUE,
> stattab=>'sm_stattab', statid=>'CUSTOMERS09270906', statown=>'SOE')
>
>
> Table name Owner NUM_ROWS BLOCKS Size
> (m) LAST_ANALYSED
> ------------------------------ ---------------- ---------- ----------
> -------- -------------------
> CUSTOMERS SOE 36364 368
> 3 09/27/2006 08:39:50
>
>
> But still the clust factor reported by dba_indexes for CUSTOMERS_PK is
> inferiors to CUSTOMERS block count.
>
>
> Table Index
> Column Clust Distinct
> Name Name U Name
> Factor Keys NUM_ROWS
> -------------------- ------------------------------ - --------------------
> ---------- ---------- ----------
> CUSTOMERS CUSTOMERS_PK U CUSTOMER_ID
> 345 36112 36112
>
> This is oracle 10.1.0.4
>
>
> B. Polarski
>

-- 
Best Regards,
Syed Jaffar Hussain
8i,9i & 10g OCP DBA

I blog at :http://jaffardba.blogspot.com/

http://www.oracle.com/technology/community/oracle_ace/ace1.html#hussain
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