ibmi-rpg-flow

name	ibmi-rpg-flow
description	Explain how an RPG program executes step by step from entry point to end of processing

Explain the runtime execution flow of IBM i RPG programs in chronological order, showing how the program behaves from start to finish.

Analyze the program structure: - Identify source style (fixed-form, free-form, or mixed) - Determine entry model (mainline, main procedure, cycle-driven, or exported procedure) - Identify data inputs (parameters, files, data areas, SQL cursors, external calls) - Map execution blocks (initialization, validation, main loop, updates, error handling, cleanup) Program Overview section: - Brief statement of program purpose and responsibility - Type of program (interactive, batch, service program module, REST API) - Key dependencies (files, service programs, external calls) Entry Point and Initialization: - How execution starts (call, cycle, procedure invocation) - Parameters received and their purpose - Initial setup work (file opens, variable initialization, *INZSR subroutine) - Control options that affect behavior Step-by-Step Execution Flow: - Number each major step in chronological order - Explain what happens at each step - Show decision points (IF, SELECT, DOW, DOU conditions) - Identify loops and what drives them (EOF, counter, condition) - Highlight branching logic and why it matters - Note when control moves to subroutines or procedures Data Operations: - When database reads occur (READ, CHAIN, SQL SELECT) - When updates happen (UPDATE, SQL UPDATE) - When inserts occur (WRITE, SQL INSERT) - When deletes happen (DELETE, SQL DELETE) - File positioning operations (SETLL, SETGT) - SQL cursor operations (DECLARE, OPEN, FETCH, CLOSE) Special Handling: - Indicator usage and their meaning - Control breaks (L1-L9, LR) - End-of-file behavior - Error handling (MONITOR/ON-ERROR, SQLCODE checks, *PSSR) - Display file or printer file output timing Exit Point: - How processing ends (RETURN, *INLR, end of mainline) - Cleanup operations (file closes, resource release) - Return values or output parameters - Final status indicators Data Flow Summary: - Visual or textual summary of the processing path - Key technical details about implementation - Performance considerations if relevant

Fixed-Form Specifics:

• Respect column positions when interpreting code
• Explain specification types (H, F, D, I, C, O, P)
• Pay attention to indicators and conditioned operations
• Detect and explain cycle-based behavior
• Clarify implicit processing when cycle drives execution

Free-Form Specifics:

• Use declarations to understand scope and dependencies
• Follow procedure calls and loops in logical order
• Distinguish initialization from business logic
• Explain MONITOR blocks, SQL handling, and return paths

IBM i Terminology: Use proper IBM i terms: libraries, source files, members, stream files, job, activation group, record format, indicator, control break, library list.

Guardrails:

• Do not invent code paths not present in source
• Do not assume business meaning unsupported by code
• Focus on declarations that affect flow, not all equally
• Translate technical branching to business behavior
• Summarize repeated patterns instead of repeating explanations
• Do not rewrite code unless explicitly requested