Flowchart - Process diagram

Enhanced Definition

A flowchart is a graphical representation of a process, algorithm, or workflow. In the mainframe context, it visually depicts the sequence of operations, decisions, and data flows within a batch job, online transaction, program logic, or system architecture on z/OS, aiding in understanding, designing, documenting, and debugging complex systems.

Key Characteristics

- Standardized Symbols: Utilizes a set of predefined graphical symbols (e.g., rectangles for processes, diamonds for decisions, parallelograms for I/O, arrows for flow) to represent different types of operations and their sequence.
- Sequential Flow: Clearly illustrates the logical order in which steps are executed, typically from top to bottom or left to right, using directional arrows.
- Decision Points: Explicitly shows conditional logic and branching paths using diamond symbols, which are crucial for representing IF/ELSE logic in COBOL or COND parameters in JCL.
- Input/Output Representation: Differentiates between data input and output operations, vital for understanding data handling in mainframe batch jobs, utility steps, or transaction processing.
- Clarity and Readability: Aims to simplify complex logic into an easily understandable visual format, facilitating communication among mainframe developers, analysts, and operations staff.
- Hierarchical Design: Can be used to represent processes at various levels of detail, from high-level system overviews to granular program logic within a single module.

Use Cases

- COBOL Program Logic Design: Designing the internal logic of a COBOL program, including loops (PERFORM), conditional statements (IF/ELSE), and subroutine calls (CALL), before writing the actual code.
- JCL Job Stream Definition: Mapping the sequence of job steps, conditional execution (COND parameter), and data set dependencies within a complex JCL job stream for batch processing.
- Batch Application Workflow Documentation: Illustrating the end-to-end flow of a multi-step batch application, showing data handoffs between programs, utility steps, and external systems.
- CICS Transaction Flow Analysis: Documenting the interaction between CICS programs, screen maps (BMS), database calls (DB2/IMS), and temporary storage within an online transaction.
- System Architecture Overview: Providing a high-level visual representation of how different mainframe components (e.g., CICS regions, DB2 subsystems, IMS control regions, batch jobs) interact within an enterprise solution.

Related Concepts

Flowcharts are fundamental tools used throughout the System Development Life Cycle (SDLC) for mainframe applications, particularly during the analysis and design phases. They serve as a visual alternative or complement to Pseudo-code for representing program logic, often preceding the actual coding in COBOL, PL/I, or Assembler. In the context of JCL, flowcharts visually map the execution flow and dependencies that are textually defined using EXEC PGM= statements, DD statements, and COND parameters. They are also essential for documenting the operational procedures for batch processing and online transaction processing (OLTP) systems like CICS and IMS, ensuring clarity for both development and operations teams.

Best Practices:

Adhere to Standard Symbols: Consistently use ANSI/ISO standard flowchart symbols to ensure universal understanding and avoid ambiguity among mainframe professionals.
Keep it Concise and Modular: Avoid overly complex or "spaghetti" flowcharts; break down large processes into smaller, more manageable sub-flowcharts or modules.
Add Annotations and Comments: Use text annotations to clarify specific steps, decision criteria, data transformations, or mainframe-specific logic (e.g., abend conditions, specific utility parameters).
Maintain Current Documentation: Ensure flowcharts are updated whenever the corresponding mainframe program, JCL, or system logic changes to prevent discrepancies and maintain accurate system documentation.
Review with Peers and Stakeholders: Have other mainframe developers, system architects, and business analysts review flowcharts to catch errors, identify potential issues, and ensure accuracy and completeness.
Integrate with Other Design Artifacts: Link flowcharts to related design documents, program specifications, JCL listings, data models (e.g., for DB2 or IMS), and test plans for comprehensive system understanding.