Automatic Segment Space Management

Automatic Segment Space Management

Prior to 9i, you had to manage space manually by the PCTFREE, PCTUSED, and FREELIST GROUPS parameters. 9i makes these parameters obsolete because its automatic segment space management uses bitmaps instead of freelists.

To use this feature, the tablespace must be locally-managed and you must use the SEGMENT SPACE MANAGEMENT clause:

CREATE TABLESPACE my_ts
DATAFILE ‘d:\oracle\oradata\orcl\test.dbf’ size 10M
EXTENT MANAGEMENT LOCAL
SEGMENT SPACE MANAGEMENT AUTO ;

View DBA_TABLESPACES lists whether segment space management is AUTO or MANUAL. Use the new DBMS_SPACE package procedure SPACE_USAGE to view information about free blocks in automatically space-managed (ASM) segments.

Note that the ALTER TABLE command does not update the bitmap blocks (BMBs) if you use it to update PCTFREE for ASM segments. Run the new procedure DBMS_REPAIR.SEGMENT_FIX_STATUS to remedy this problem.