CREATE_BITMAP_AREA_SIZE

Property	Description
Parameter type	Integer
Default value	8388608 (8 MB)
Modifiable	No
Range of values	Operating system-dependent
Basic	No

Note:

1. Oracle does not recommend using the CREATE_BITMAP_AREA_SIZE parameter unless the instance is configured with the shared server option. Oracle recommends that you enable automatic sizing of SQL working areas by setting PGA_AGGREGATE_TARGET instead. CREATE_BITMAP_AREA_SIZE is retained for backward compatibility.

CREATE_BITMAP_AREA_SIZE is relevant only for systems containing bitmap indexes. It specifies the amount of memory (in bytes) allocated for bitmap creation. The default value is 8 MB. A larger value may speed up index creation.

Cardinality is the number of unique values in a column in relation to the number of rows in the table. If cardinality is very small, you can set a small value for this parameter. For example, if cardinality is only 2, then the value can be on the order of kilobytes rather than megabytes. As a general rule, the higher the cardinality, the more memory is needed for optimal performance.

2. Related: BITMAP_MERGE_AREA_SIZE

This parameter is not dynamically alterable at the session level.

3. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = ‘CREATE_BITMAP_AREA_SIZE’;

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
create_bitmap_area_size	8388608	TRUE	FALSE	FALSE	FALSE	FALSE	size of create bitmap buffer for bitmap index

Oracle initializatoin parameters