Open RSE
Right-click on the program to debug, and “Set Entry Point”
Start the program in the usual way
When the program starts, RSE will switch to debug mode.

Steps:
1.compile the pgm with source option.
2.submit the job
3.start service job (do wrkactjob,select your job,type 5,copy the job number as u will need this in this option)
4.do strdbg,put a break point by F6.If multiple call are there put F2 to include them as well.
5.come out.
If in 4 th step ur not allowed to enter breakpoint.Then release the job from other AS400 ID.
Do DSPMODSRC.Put breakpoint.Wait for few minutes for debug screen to appear.

Follow the below steps:

1, Compile the program with Source option and use SBMJOB command and take f10 option for addiotional parameters.
2. Set the Hold on job queue to *Yes
3. Give WRKSBMJOB command and take option 5 to note down the job attributes.
4. Give STRSRVJOB command and the necessary details.
5. Give STRDBG command and the programs to debug.
6. The source will be listed once the above option is given, try to add break points(message will be displayed as break points cannot be added when job is on hold).
7. Come back to the job that is submitted and give option 6 to release it and wait for sometime.
8. Give the DSPMODSRC command, the source will be displayed, add break points and do the debug now.