RE: Bitmap Indexes sizes

From: Steve Adams <steve.adams_at_ixora.com.au>
Date: Wed, 18 Apr 2001 16:05:14 -0700
Message-ID: <F001.002EC487.20010418145629@fatcity.com>

Hi Darren,

Yes, this sort of space blow-out is to be expected for a bitmap index on a volatile table. It is not so bad with more recent versions, and the MINIMIZE RECORDS PER BLOCK syntax can help. If the snapshot is manually refreshed, you will do better to drop this index prior to each refresh. Otherwise, a simple (aka B*-tree) index should be considered.

@ Regards,
@ Steve Adams
@ http://www.ixora.com.au/
@ http://www.christianity.net.au/

-----Original Message-----
Sent: Thursday, 19 April 2001 8:15
To: Multiple recipients of list ORACLE-L

I have (had) an index that according to index_stat (after analyze index) and dba_extents that
reported to be approximately 53 Mb and took up 11 extents. The percentage increase is 50.

I dropped the index and recreated it, after I adjusted the initial extents, it turns out the final size
is less then 500k. This seems like a large amount for it to drop.

The index is on a snapshot within our data warehouse.

Has anybody else seen this ?? Is this a problem with bitmap indexes. ??

Thanks

Darren

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Darren Browett P.Eng                                    This message was
transmitted
Systems Admin/DBA                                       using 100% recycled

electrons
Information and Communications Technology. City of Coquitlam
P:(604) 927 - 3614
E:dbrowett_at_city.coquitlam.bc.ca

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Received on Wed Apr 18 2001 - 18:05:14 CDT