The following situation triggers the restoration of optimizing information:

• After optimizing information was updated, there was a decrease in performance.

The following is the procedure for restoring optimizing information.

Procedure

1. Determine the table whose optimizing information you wish to restore.
   From the SQL statement whose performance has decreased, identify the tables whose optimizing information needs to be restored.
   
2. Prepare the parameter file that contains optimized information to be used for the restoration.
   Prepare the parameter file that contains optimized information, which was saved as a backup before the optimizing information was updated.
   For details about updating optimizing information, see 19.2.2 Updating optimizing information.
   There are some issues that you need to take into account when you prepare the parameter file that contains optimized information. For details, see 19.4.1 Using a parameter file that contains optimized information after table and index definitions are modified.
   
3. Delete the optimizing information as needed.
   See 19.4.2 Using pdgetcst after optimizing information is saved, and restoring optimizing information to determine whether the optimizing information can be deleted. Then, delete it as needed. For details about deleting optimizing information, see 19.2.4 Deleting optimizing information.
   
4. Restore the optimizing information.
   Use the pdgetcst command and a parameter file that contains optimized information to register optimizing information. For details, see 19.3.2 Registering optimizing information by using a parameter file that contains optimized information.
   Command execution example:
   This example restores the optimizing information for table USER1.T1 by using a parameter file that contains optimized information (/tmp/optinfo_20101014) that was saved. A pdgetcst command execution example for this operation follows:
   

   pdgetcst -s /tmp/optinfo_20101014 -a USER1 -t T1