Development

Enhanced Definition

In the mainframe context, development refers to the entire process of designing, coding, testing, and implementing software applications or system components that run on IBM z/OS and related platforms. This primarily involves creating or modifying programs written in languages like COBOL, PL/I, Assembler, and REXX, often interacting with core mainframe subsystems such as CICS, DB2, and IMS.

Key Characteristics

- Language Specificity: Predominantly utilizes established mainframe programming languages such as COBOL for business logic, PL/I for scientific or system programming, Assembler for high-performance or low-level tasks, and REXX for scripting and automation.
- Integrated Development Environment (IDE): Often performed using TSO/ISPF for editing, compiling, and debugging, sometimes augmented by modern Eclipse-based IDEs like IBM Developer for z/OS (IDz).
- Batch and Online Processing Focus: Development targets both long-running, high-volume batch applications (e.g., financial processing, reporting) and high-transaction-rate online applications (e.g., customer service, point-of-sale) managed by CICS or IMS TM.
- Robustness and Performance: Emphasizes creating highly stable, performant, and scalable applications capable of handling millions of transactions or processing terabytes of data with strict service level agreements (SLAs).
- Legacy Integration: Frequently involves enhancing, maintaining, or integrating with existing mission-critical legacy systems, requiring deep understanding of established codebases and data structures.

Use Cases

- New Application Development: Creating new batch processing jobs for daily, weekly, or monthly cycles (e.g., payroll, billing, inventory updates) using COBOL and JCL.
- Online Transaction Processing (OLTP): Developing or modifying CICS or IMS TM programs to support real-time user interactions, such as banking transactions, airline reservations, or insurance policy lookups.
- System Utilities and Automation: Writing REXX scripts or Assembler routines for system administration tasks, data manipulation, or automating operational procedures within z/OS.
- Database Application Development: Building applications that interact with DB2 for z/OS or IMS DB databases, involving embedded SQL or DL/I calls within COBOL or PL/I programs.
- API and Integration Development: Creating z/OS applications that expose or consume RESTful APIs, often using z/OS Connect EE or other integration middleware to bridge with distributed systems.

Related Concepts

Development is intrinsically linked to the entire Software Development Life Cycle (SDLC) on the mainframe. It relies heavily on JCL for job execution and resource allocation, COBOL or PL/I for the application logic, and CICS or IMS for transaction management. DB2 and IMS DB provide the data persistence layer. Version control systems like CA Endevor or IBM z/OS Change Tracker are essential for managing source code, while TSO/ISPF serves as the primary interface for developers.

Best Practices:

Adhere to Coding Standards: Implement strict coding standards, naming conventions, and modular design principles to ensure maintainability, readability, and consistency across the codebase.
Thorough Testing: Conduct comprehensive unit, integration, system, and user acceptance testing (UAT) using realistic test data and environments to identify and resolve defects early.
Leverage Change Management Systems: Utilize robust change management and version control systems (e.g., CA Endevor, IBM z/OS Change Tracker) for source code management, promotion, and auditability.
Performance Optimization: Design and code with performance in mind from the outset, optimizing SQL queries, I/O operations, and CPU utilization to meet stringent mainframe performance requirements.
Security by Design: Incorporate security considerations throughout the development process, including proper authorization checks (RACF, ACF2), data encryption, and secure coding practices to protect sensitive data and systems.