SQL> select BYTES,BLOCKS,EXTENTS from user_segments where segment_name ='EMP';

BYTES BLOCKS EXTENTS
---------- ---------- ----------
2621440 640 11

SQL> analyze table emp compute statistics;
Table analyzed.
SQL> select BLOCKS,EMPTY_BLOCKS from user_tables where table_name='EMP';
BLOCKS EMPTY_BLOCKS
---------- ------------
579 60


(Ie 60 blocks are free)

SQL> delete from emp;
98304 rows deleted.
SQL> commit;
Commit complete.
SQL> alter table emp deallocate unused;
Table altered.
SQL> select BYTES,BLOCKS,EXTENTS from user_segments where segment_name ='EMP';
BYTES BLOCKS EXTENTS
---------- ---------- ----------
2375680 580 11


ie 640 - 60 = 580. Just released the empty blocks


Thomas