Analyzing the Statistics 

Reorganization is not required as often as is commonly assumed. This can be briefly explained with the following considerations.

A reorganization should be considered when total system performance declines due to a large number of extents of a table or an index. If many of the objects consist of a large number of extents, reorganize the relevant table, index, or the entire tablespace.

If, however, none of the remaining fragments is large enough to create a new extent, you should extend the tablespace and possibly schedule a tablespace reorganization at a later time that is suitable.

Also see Limitations of the Database System.