Re: Experience in bitmap index in Oracle 7.3

> Can somebody tell me how I can use bitmap indexing in Oracle 7.3. and
> where I can find it in the documentation ?

Bitmap indexes are certainly cool. Available with 7.3, the versions prior to 7.3.3 don't permit inserts to update the bitmap indexes. You have to periodically rebuild the indexes. The feature is intended for decision support applications, where you have relatively few distinct values on a particular column. If multiple columns are included in a where clause, each with bitmaps, and the combined 'AND' condition results in a small number of rows to select, bitmaps can be advantageous. On the other hand, if you have only a couple of columns that qualify for a bitmap index (ie, having few distinct values), then you might as well do full table scans.

Documentation is contained in the 7.3 Tuning Guide. Some of the online docs for 7.3 servers still have the 7.2 Tuning Guide, so you have to hunt and then call Oracle. They might fax you the 3 or so pages that apply to bitmaps. Oracle also has info on some init.ora parameters you have to set to get bitmaps to work for 7.3.2, etc.

There is a white paper on the Oracle web site, www.oracle.com, which discusses bitmaps, but not in much technical detail. Read, get to know the concept, and then experiment.

Roger Received on Tue Mar 04 1997 - 00:00:00 CET