Re: Shrinking an index??

dathedba_at_mindspring.com (Doug Anderson) wrote:

> Hey,
> How about using a BITMAP index found in 7.3.2.3? It has saved me
> great amounts of disk space. A number of my indexes were over 400 Meg
> in size before changing to BITMAP and are now around 69 Meg each.
> BITMAPs are useful for 'low cardinality' indexes (ie. those with
> low number of distinct values compared to the total number of rows in
> the table). To find out about the cardinality do an ANALYZE on the
> index then check the DISTINCT_KEYS column in DBA_INDEXES.
> It is well worth the effort of upgrading to 7.3.2.3!
> -Doug Anderson
> DAtheDBA_at_mindspring.com

        For which rate of low cardinality do you think that is useful to use bitmap indexes?           

        Regards,

--
Luis Santos
Relacional Consultoria
Rio de Janeiro - Brazil