Primary files are used to force the RPG program to use the program cycle – these days they are very rarely used.
Using the program cycle can be very confusing to people used to structured programming – best to avoid it as much as possible – in other words don’t use it unless you know what you’re doing and have a good reason for using it. (I can’t think of one right now).
Absolutely right .. unless you need to do maintenance on existing programs.
The primary file is automatically read by the cycle.