I know nothing about either but I would think the issue is not in DB2 (being a high end multiuser db) but within how RPG is accessing the data, e.g. maybe applying a table lock so it ensures nothing changes in a table while it generates a report. I would have a close look at how RPG is configured.
Cheers, Peter
If it's not a configuration issue with the RPG program, then it certainly be too much of a hassle (and most likely not possible) for the RPG program to be changed so that it locks the row differently, so that's probably not an option.
Some row locks allow you to read the data while the row is locked, but I don't know enough about DB2 or the way that the RPG program is locking the row to definitively tell you what to do.