Oracle Database 10g Release 2 has come up with feature improvements for automatic segment-space management. In Release 1, you had to turn on automatic segment-space management, whereas in Release 2, ASSM is set to AUTO. The advantage is that tablespaces have automatic segment-space management turned on by default, as soon as they are created.
Space-management features have been enhanced to identify empty data files and drop them. Segment Advisor can automatically identify tables and indexes that need to be compressed to reclaim free space. For Release 2, Segment Advisor is tightly integrated with segment findings to cover non-ASSM tablespaces and chained rows in them.