Using Automatic Undo Management
Oracle introduced automatic undo management in Oracle 9i. This feature has been significantly improved in Oracle Database 10g; in addition, the Undo Advisor tool has been introduced. To run your database in automatic undo management mode, you should set the UNDO_MANAGEMENT initialization parameter to AUTO.
Oracle makes a copy of the original data in the database before modifying it. This is helpful if you ever wish to roll back any database changes. Oracle writes these change vectors to undo the operation. The original copy of the data before any modification is called the undo data. This undo data is stored in an undo tablespace. The automatic undo management feature automatically determines the retention period ...
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