UNDO SPACE ACQUISITION AND MANAGEMENT

When you open the database , the instance e attempts to acquire one or more tablespaces or roll back, segments you determine whether to operate in automatic undo management mode or manual undo management mode at instance start up using the UNDO_MANAGEMENT initialization parameter. The supported values are AUTO or MANUAL, if AUTO , then the instance is started in automatic undo management mode. The default value is MANUAL.


1) If you use the undo tablespace method, you are automatic, undo management mode,. This is recommended.

2)If you use the rollback segment method of managing undo sapce, then you are using manual undo management mode.