This chapter reviews the various methods for improving the performance of your SQL statements. Monitoring and measuring tools, such as Debug and the GUI Visual Explain are reviewed. The significance of the query attribute file (QAQQINI) is discussed. The role of indexes within an SQL database is also covered. All these topics relate to the relative performance of an SQL statement—that is, never to its ability to run, only the speed at which it runs.
Debug is the easiest performance monitoring tool to use and the most familiar for developers of traditional applications on the iSeries. To start Debug, simply initiate a 5250 session and key in the command:
This activates the interactive ...