Free space can be managed automatically or manually.
Free space can be managed automatically inside database segments. The in-segment free/used space is tracked using bitmaps, as opposed to free lists. Automatic segment-space management offers the following benefits:

• .Ease of use
• Better space utilization, especially for the objects with highly varying row sizes
• Better run-time adjustment to variations in concurrent access
• Better multi-instance behavior in terms of performance/space utilization

You specify automatic segment-space management when you create a locally managed tablespace. The specification then applies to all segments subsequently created in this tablespace.

第3,4点不太明白是什么意思

运行时调整？ 多实例行为?