Which of the following advisors is run in every maintenance window by the auto-task system?

Answer: D

Explanation: Answer option D is correct. The SQL Access Advisor is an ADDM diagnostic advisor that provides additional support to find out the potential schema modifications. These potential schema modifications can be used to reduce the amount of I/O, CPU, and wait time for a given SQL statement. The advisor also makes potential suggestions about indexes and materialized views to improve the system performance. The SQL Access Advisor and the Segment Advisor run in every maintenance window by the autotask system. However, implementing the recommendations is up to a DBA. A is incorrect. The Memory Advisor is used to collect information about Oracle's memory structures inclusive of the System Global Area (SGA) and user memory structures. B is incorrect. The SQL Tuning Advisor is an ADDM diagnostic advisor that formulates more efficient SQL execution plans for a particular SQL statement. The advisor accepts a SQL statement as input and gives the advice on the execution of the SQL statement, the estimated performance benefit, and the actual command in order to improve its efficiency. C is incorrect. The Undo Advisor is an ADDM diagnostic advisor that is used to determine appropriate sizing for Undo tablespaces and also helps in determining optimal UNDO_RETENTION settings. This advisor helps prevent the snapshot too old error. It also sets a threshold value for undo retention period, helps find out the issues related to the undo tablespace and provides recommendations to correct these issues.