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SQL Optimizer for DB2 LUW 4.4 - Installation Guide

Selected SQL

ClosedView the Batch Run Criteria Window—Selected SQL/Index Set

The Selected SQL/Index Set tab of the Batch Run Criteria window is used to select the SQL and index-set alternatives you want to execute. By default, all alternatives are initially selected. 

Tip: To save all settings on the Batch Run Criteria dialog for subsequent batch runs, select Save setting for the next batch run.

Selecting SQL statements to test

To select or deselect an alternative

Double-click an SQL or index-set alternative.

To select or deselect all alternatives 

Right-click and select Select All or Unselect All.

To select alternatives according to the cost values

  1. Select the Apply SQL/Index Sets selection filter checkbox.

  2. Click SQL/Index Sets selection filter image\B_SQLSelectionFilter.gif.

  3. Review the DB2 LUW cost retrieved from the virtual plans.

  4. Check the Exclude SQL/Index Set with DB2 LUW cost greater than checkbox and enter a DB2 LUW cost.

Note: The original SQL statement can be de-selected only if the Original SQL option is not selected in the SQL Termination tab of the Batch Run Criteria window and the Always run Original SQL first option is not selected.

Changing the execution order of alternatives

The alternatives are ranked by DB2 LUW Cost by default, with the exception of the original SQL, which is placed at the top.

To change the execution order using the DB2 LUW cost

Click either the DB2 LUW or the SQL/Index Set column heading to reorder the alternatives for execution.

Note: High DB2 LUW Cost does not necessarily mean slower performance. If possible, it is recommended that all alternatives be tested.

To change the execution order for individual alternatives

Select the SQL or index-alternative; then click Move Up image\B_MoveUp.gif or Move Down image\B_MoveDown.gif.

Always run Original SQL first

The original SQL statement can always be run first even if it does not have the lowest DB2 LUW cost.

To always run the original SQL statement first

Select the Always run Original SQL first checkbox.

This checkbox is disabled if Original SQL is selected as a termination criterion on the SQL Termination tab or the Batch Termination tab since the run time from the original SQL is going to be used to terminate the alternatives or to terminate the Batch Run itself. In this case, you must run the original SQL statement first to obtain the termination time.

 

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