BITMAP_MERGE_AREA_SIZE

Property	Description
Parameter type	Integer
Default value	1048576 (1 MB)
Modifiable	No
Range of values	Operating system-dependent
Basic	No

Note:

1. Oracle does not recommend using the BITMAP_MERGE_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. BITMAP_MERGE_AREA_SIZE is retained for backward compatibility.

2. BITMAP_MERGE_AREA_SIZE is relevant only for systems containing bitmap indexes. It specifies the amount of memory Oracle uses to merge bitmaps retrieved from a range scan of the index. The default value is 1 MB. A larger value usually improves performance, because the bitmap segments must be sorted before being merged into a single bitmap.

3. Related: CREATE_BITMAP_AREA_SIZE

This parameter is not dynamically alterable at the session level.

4. 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) = 'BITMAP_MERGE_AREA_SIZE';

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
bitmap_merge_area_size	1048576	TRUE	FALSE	FALSE	FALSE	FALSE	maximum memory allow for BITMAP MERGE

Oracle initializatoin parameters