RE: bitmap indexes going wild

In my past assignment with AT&T Solutions, Oracle consulting designed their Customized Datawarehouse and used lot of bitmap indexes. However at data load time, they were dropping those indexes and recreate them after the load. Besides there was a problem with 7.3.4.0 with inserts on table with Bitmap Indexes which were growing without any limit so as a work around also, they were dropping before inserts and then recreating it.

MOHAMMAD RAFIQ Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Mon, 30 Jul 2001 09:10:26 -0800

They way Oracle uses bitmap indexes, they are very poor performance when doing large writes, or data loads.
Oracle actually shys away from their use for OLTP environments.

Although bitmap indexes are very cool and can have very significant performance gains, you must be very careful with them, they do not perform as consistent as b-tree indexes and can sometimes pose performance problems due to their increased complexity on writes.

"Walking on water and developing software from a specification are easy if both are frozen."

Christopher R. Spence
Oracle DBA
Fuelspot

-----Original Message-----
Sent: Monday, July 30, 2001 10:31 AM
To: Multiple recipients of list ORACLE-L

Hi Stephane,

your data loads will also be much much quicker if you drop your bitmap indexes prior to the load. But then you have to weigh the speed increase of your load against the time it will take to rebuild the bitmaps. I believe the doco discusses why bitmaps can slow down inserts.

Lisa Koivu
Oracle Database Administrator
Fairfield Resorts, Inc.
954-935-4117

        -----Original Message-----
Sent: Monday, July 30, 2001 10:00 AM
To: Multiple recipients of list ORACLE-L

        Stéphane,
I have seen such behaviour with bit mapped index since 7.3.4.x. The index did not grow as much in 8.x versions. But it was still unacceptable. We drop

all bit mapped indexes prior to data loads and rebuild them afterwards.

        Regards,

• Kirti Deshpande Verizon Information Services http://www.superpages.com <http://www.superpages.com>

        > -----Original Message-----
> From: paquette stephane [SMTP:stephane_paquette_at_yahoo.com]
> Sent: Monday, July 30, 2001 8:30 AM
> To: Multiple recipients of list ORACLE-L
> Subject: bitmap indexes going wild
>
> Hi,
>
> 3 bitmap indexes have gone pretty big during data
> insert. Once rebuild they returned to their normal
> size.
> They were previous loads whitout any problem.
>
> This is on Oracle 816 64bit/Solaris 5.7
> I checked on metalink but found nothing.
> Is there any known problems with bitmap indexes on 816
> 64bit.
>
> I know I can disable the index and use
> skip_unusable_indexes but since .
>
> =====
> Stéphane Paquette
> DBA Oracle, consultant entrepôt de données
> Oracle DBA, datawarehouse consultant
> stephane_paquette_at_yahoo.com
>
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