Explanation/Reference:
Explanation:
About Automated Maintenance Tasks (link)
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.
See Also:
Oracle Database Performance Tuning Guide for more information on automatic statistics collection 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.
See Also:
"Using the Segment Advisor" for more information.
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.
See Also:
Oracle Database Performance Tuning Guide for more information on SQL Tuning Advisor By default, all three automated maintenance tasks are configured to run in all maintenance windows.