052-41

You have recently collected statistics on certain objects of a schema in your database. But you observe suboptimal execution plans for the queries on these objects after two days of statistics collection. The optimizer statistics retention period is set to its default value. Which action would help to use the previous set of statistics on the objects?
A. Restore statistics from statistics history.
B. Reduce the optimizer statistics retention period by 2 days.
C. Set the OPTIMIZER_PENDING_STATISTICS parameter to TRUE.
D. Reduce the Automatic Workload Repository (AWR) retention period by 2 days.

　　A,正确，可以从统计信息的历史信息恢复统计信息。如下面这个储存过程，RESTORE_TABLE_STATS Procedure，可以帮助你恢复原来的统计信息。