What you are looking for is, I suspect, part of an application which is running on your AS/400. It does not have anything to do with the method used to access the AS/400 (that is, Rumba).
You need to talk to your IT department. They should be able to give you information about the application. If this application is provided by an outside supplier, they may have to contact the supplier for the necessary information.
There are ways to see what files are open in your job. Easiest (in your screen job) is to perform a System Request – in IBM Client Access this is Alt+Escape. This gives you an input line at the bottom of the screen. Type the figure 3 and press Enter. You will get the Display Job menu. Option 14 shows you all the files that are open in your job. Maybe you can get a clue from that list.