three predefined automated maintenance tasks

Oracle Database has three predefined automated maintenance tasks:


Automatic Optimizer Statistics Collection—Collects optimizer statistics for all schema objects in the database for which there are no statistics or only stale statistics. The statistics gathered by this task are used by the SQL query optimizer to improve the performance of SQL execution.


Automatic Segment Advisor—Identifies segments that have space available for reclamation, and makes recommendations on how to defragment those segments.


You can also run the Segment Advisor manually to obtain more up-to-the-minute recommendations or to obtain recommendations on segments that the Automatic Segment Advisor did not examine for possible space reclamation.


Automatic SQL Tuning Advisor—Examines the performance of high-load SQL statements, and makes recommendations on how to tune those statements. You can configure this advisor to automatically implement SQL profile recommendations.


By default, all three automated maintenance tasks are configured to run in all maintenance windows.