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Section 5: Managing Optimizer Statistics > Using Historical Statistics
Using Historical Statistics
Whenever statistics are updated, the previous statistics are filed away for future use, if needed. One has the option to then restore the previously collected statistics and put them into use once again. This is useful in situations where newly collected statistics do not lead to an optimal execution plan, and you want to revert to previously collected statistics from which acceptable performance was realized.
Example
In this example, the statistics restored for the specified table will be as of the timestamp indicated.
The DBMS_OPTSTAT_OPERATIONS view contains the history of all schema-level and database-level statistics gathering operations.
By querying this view and then using the timings shown one can decide which set of historical statistics for a given object or target might be useful.