A program must be compiled using the -deb option before it can be run under the control of the debugger. This is because the compiler generates a data base file referred to as the STB file. This file contains symbolic information that the debugger needs to reference to manipulate source program symbols and entities; set breakpoints, tracepoints, and watchpoints; and control program execution. A program is referred to as being compiled in debug mode when one or more of the program modules have been compiled with the -deb option.
For example, a PL/I program contained in a source file named primes. pl1 is compiled in debug mode by entering the following command line:
mfplx primes.pl1 -deb