[SAP] Debugging background job, Running or Finished.

A short version first.

Debug Finished Job.
Go to SM37, pointing at the job you want to debug and type JDBG at the command box (where you typed in the Tcode).


Debug Running Job.
This is a little bit tricky, it the job finished too fast you wouldn't be able to debug properly. One workaround is to add "WAIT UP TO 30 SECONDS" in your ABAP code at the point where you want to debug. This can buy you some time to do the following:
Go to SM66, point at the job you want to debug, press the Debugging button or right click -> debugging.


If in normal debugging it won't stop at the break point even you tick the System Debugging & Update Debugging in Settings -> Change Debugger Profiles/ Settings,
You can try the above.