Quest SQL Optimizer for IBM® DB2® LUW maximizes SQL performance by automating the manual, time-intensive and uncertain process of ensuring that SQL statements are performing as fast as possible. SQL Optimizer analyzes, rewrites, and evaluates SQL statements within multiple database objects, files. With SQL Optimizer, you can analyze and optimize all your problem SQL from multiple sources. SQL Optimizer also provides you a complete index optimization and plan change analysis solution, from index recommendations to simulated index impact analysis, through comparison of multiple SQL access plans.
SQL Optimizer provides you with the following main modules.
SQL Optimizer (including SQL Rewrite and Generate Indexes functions)
SQL Functions are available in evaluating index-set and SQL alternatives. These functions are:
Run Result (SQL alternatives only)
The access plan is a combination of steps the optimizer chooses in order to execute a SQL statement. It is the ordered set of steps required to carry out the query with the operators chosen for each table.
To view only the access plan of the original SQL statement
From the SQL Information pane, click 
Note: The Rewrite SQL, Generate Indexes, Run for All Records, Run for First Record, and Run Result functions also retrieve the corresponding access plan.
Note: This feature is available for only SQL alternatives, not index-set alternatives.
To retrieve the SQL statement results from the database
In the SQL Optimizer window, select the SQL alternative, and click 
If the SQL statement contains a result set, the SQL Result window displays, showing all data retrieved. Otherwise, an information dialog box showing the number of rows affected displays.
In the SQL Result window, the first rows of the result set are displayed as soon as they are returned from the database. Therefore, the time it takes for you to see the result does not equal the time measured by the run- time functions to retrieve either the first record or all records run time. Run Result only retrieves enough records to display in the window; the complete result set is not retrieved until you view the last records.
To terminate the Run Result process
Click 
Two types of action, commit or rollback, can be made after the Run Result has been executed for a UPDATE, INSERT, or DELETE SQL statement depending on which window you are in when you execute the Run Result function.
When you retrieve run results for the original SQL statement (displayed as <Edit SQL>), you are prompted to commit or rollback for UPDATE, INSERT, and DELETE SQL statements.
For the SQL alternatives, all rows affected by UPDATE, INSERT, and DELETE SQL statements are rolled back automatically.
When you log on to DB2 LUW from SQL Optimizer, it connects to the database and maintains this database connection throughout the application execution. Another database session is required for the Run Result processing. This connection is established when the Run Result function is executed and dropped after all the records have been retrieved.
