Improve performance of procedures and functions

When creating stored procedures and user-defined functions (UDFs), the SQL procedural language processor on the iSeries™ does not always generate the most efficient code. However, you can do some changes to reduce the number of database engine calls needed and improve performance.

Some changes are in the design of a routine and some are in the implementation. For example, differences between how the C language compiler handles host variables and the way the SQL procedural processor requires the host variables to be handled can cause many calls to the database engine. These calls are very expensive and, when done many times, can significantly degrade performance.

Improve implementation of procedures and functions
These recommendations can be seen as simple coding techniques that can help reduce the processing time of a function or procedure. These tips are especially important to follow in functions, as a function will tend to be called multiple times from many different procedures.
Redesign routines for performance
Even following all of the implementation tips, sometimes a procedure or function may still not perform as well as it needs to. In that case, you need to look at the design of the procedure or UDF and see if there are any changes that can be made to improve the performance.

Parent topic: Routines