You can step through the instructions of a program by using the Start Debug (STRDBG) or Change Debug (CHGDBG) commands.
When using these commands, set the MAXTRC parameter to 1 and the TRCFULL parameter to *STOPTRC. When you specify a trace range (Add Trace (ADDTRC) command) and the program processes an instruction within that range, a breakpoint display with an error message appears. If you press Enter, another breakpoint display with the same error message appears for the next instruction processed in the trace range. When tracing is completed, the trace data contains a list of the instructions traced. You can display this data by entering the Display Trace Data (DSPTRCDTA) command.