Choosing EXPLAIN and tuning options
When you select a statement from the Scope page and click Next, you are taken to the Options page, where, you can reconfigure the default set of EXPLAIN and tuning options supported by Db2.
You can also click Tune selected statement at the top of the window to advance a selected statement to the Options page.
Expand this section to set values for Db2 special registers (EXPLAIN options), used by Db2 to create an access plan.
A special register is a storage area that is defined for an application process by Db2 and is used to store information that can be referenced in SQL statements. A reference to a special register is a reference to a value provided by the current server.
Please refer to the Special registers topic for detailed descriptions of each special register.