Debugging update/transfer rules If you suspect that there is a problem in update rules or transfer rules (example: Expected transformations are not taken place). In which case go to the data load monitor in BIW and select the data package you like to debug as shown below. Right click and select “Simulate update” . Following dialog will appear:Choose update rules/transfer rules for debugging. You can also choose the specific records you like to debug. Once you are ready, select “Perform Simulation” and enjoy the debugging of the transfer/update rules. Debugging “Start routine” Above process cannot be used to debug start routines, which get executed before the update rules are called for each data packet. And this start routine is called in the background process. Even statements like “BREAK-POINT” are ineffective in breaking the execution process. You can use the following trick in this case: Have an infinite loop in the start routine: ** for debugging purpose WHILE sy-subrc EQ 0. ENDWHILE. Trigger the data load process and the process will go into inifinite loop. You can see the process in transaction SM50 (process overview). Select the process and debug. Once you reach the while statement, change the sy-subrc to 1 and proceed with the debugging of start routine. CAUTION: Don’t forget to delete the infinite loop once you are done with the debugging.