STRDBG Basics for RPGLE

Learning Objective

By the end of this lesson, you will be able to explain what STRDBG does, what a program needs before it can be debugged this way, and what happens once the debugger starts.

Simple Explanation

The Debugging RPGLE Programs lesson mentioned STRDBG only by name. This lesson covers what actually happens when you use it.

STRDBG PGM(CUSTRPT)

Here, STRDBG PGM(CUSTRPT) (Start Debug) starts the ILE source debugger for the CUSTRPT program, opening an interactive debug display that shows the program's actual RPGLE source code. Before this works, the program needs to have been compiled with debugging data, information the compiler includes specifically so the debugger can show source lines and variable names rather than just raw machine instructions. Once STRDBG starts, the program has not actually run yet; the debugger is simply ready, waiting for the program to be called so it can pause and show what happens as it executes.

Why It Matters

STRDBG is the entry point for every other debugging technique covered in this lesson group: breakpoints, stepping, and watching variables all depend on first starting a debug session against a program compiled with debugging data. Understanding this as the necessary first step avoids the confusing experience of trying to set a breakpoint on a program that either was not compiled correctly or was never actually put into debug mode.

Practical Example

Imagine investigating the CUSTRPT report program from earlier lessons in this path, which is producing an unexpected balance total. Before looking at anything else, a developer runs STRDBG PGM(CUSTRPT), opening the debug display showing CUSTRPT's actual source. From there, as covered in the next two lessons, they can set a breakpoint at the balance calculation and step through it to see exactly what happens.

This is a simplified, illustrative example rather than a specific real investigation, but it reflects the standard first step behind almost every RPGLE debugging session on IBM i.

Common Confusions

"Does STRDBG run the program immediately?" No. STRDBG only starts the debug session and opens the source display; the program itself still needs to be called separately, at which point the debugger becomes active and can pause execution.

"What happens if I try to debug a program that wasn't compiled with debugging data?" The debugger typically cannot show meaningful source lines or variable names for that program, since the information it needs was never included at compile time. This is why compiling with debugging data is a prerequisite covered in this lesson, not an optional detail.

"Do I need to use STRDBG every single time I run a program while developing it?" No. STRDBG is specifically for when you need to actually step through or inspect a program's behavior in detail. Many ordinary test runs do not need a debug session at all.

Quick Recap

• STRDBG PGM(name) starts the ILE source debugger for a specific program, opening its source in an interactive debug display.
• A program must be compiled with debugging data before STRDBG can show its source lines and variable names meaningfully.
• Starting a debug session does not run the program by itself; the program still needs to be called separately.
• STRDBG is the necessary first step before setting breakpoints or watching variables, covered in the next lessons.

Try Asking the AI Tutor

Use the AI Tutor to ask follow-up questions about this lesson. For example, try asking:

• "How do I know whether a program was compiled with debugging data?"
• "Can I start a debug session against a program that is already running?"