Debugging with External Breakpoints 
Prerequisites
The coding must contain a known position that runs through a unit during processing.
The user under which the unit is being processed must also be known. You can find the user by positioning the cursor on the unit in question and pressing the Details (“magnifying glass”) button.
The user who the external breakpoint is set for must have debugging authorization. If this user and the one carrying out the debugging are two different users, the latter must also have this authorization.
Procedure
General
Firstly, set the external breakpoint for the user who created the bgRFC unit.
Now run the application. This schedules the unit in the bgRFC. The bgRFC processes the unit automatically (processing may be staggered, depending on the volume to be processed), and the debugger appears.
If the unit is locked, unlock it so that it can be entered and processed by the scheduler.
NoteAlternatively, you can start processing by choosing Unit Analysis
Run Unit with Runtime Analysis 
from the unit’s context menu.End of the note.
Setting Up the Application Server
An external breakpoint is set on a specific application server. If the scheduler is running on a different application server, the external breakpoint has no effect.
In this instance, proceed as follows:
Set the bgRFC Scheduler so that it runs on precisely one application server. This will ensure that setting the breakpoint on the application server in question will bring success.
NoteThis procedure prevents load distribution, however, and is therefore not recommended in a production system.
End of the note.Alternatively, you can replicate an external breakpoint from one application server to another. This procedure is described in detail in SAP Note 1004248.