Use WebSphere Development Studio Client for System i. This is the recommended method and documentation about debugging programs and appears in that product's online help. With the integrated i5/OS debugger you can debug your program running on the System i from a graphical user interface on your workstation. You can also set breakpoints directly in your source before running the debugger. The integrated i5/OS debugger client user interface also enables you to control program execution. For example, you can run your program, set line, watch, and service entry point breakpoints, step through program instructions, examine variables, and examine the call stack. You can also debug multiple applications, even if they are written in different languages, from a single debugger window. Each session you debug is listed separately in the Debug view.
In ILE, you can perform source-level debugging on any single- or mixed-language ILE application. The ILE source debugger also supports OPM programs. You can control the flow of a program by using debug commands while the program is running. You can set conditional and unconditional job or thread breakpoints prior to running the program. After you call the program, you can then step through a specified number of statements, and display or change variables. When a program stops because of a breakpoint, a step command, or a run-time error, the pertinent module is shown on the display at the point where the program stopped. At that point, you can enter more debug commands.
For information on the debugger, refer to Debugging Programs.