Implementation - Realization

Enhanced Definition

Implementation, in the mainframe context, refers to the comprehensive process of transforming a designed solution into a functional, operational component within the z/OS environment. It encompasses the coding, configuration, testing, and deployment activities required to bring a new application, system enhancement, or infrastructure change to fruition. It is the practical realization of a technical design or business requirement.

Key Characteristics

- Code Development: Involves writing or modifying source code in languages like COBOL, PL/I, Assembler, or REXX to meet specified requirements.
- JCL Creation/Modification: Requires developing or updating Job Control Language (JCL) to define job steps, allocate datasets, and execute programs on z/OS.
- Subsystem Integration: Often involves configuring and integrating with key z/OS subsystems such as CICS, DB2, IMS, MQ, or z/OS Connect.
- Rigorous Testing: Mandates multiple phases of testing, including unit, integration, system, and user acceptance testing (UAT), typically on dedicated test LPARs.
- Change Management: Adheres to strict change control procedures, often utilizing Software Configuration Management (SCM) tools for versioning and promotion.
- Deployment & Activation: Includes compiling, linking, binding, installing resources (e.g., CICS definitions, DB2 packages), and activating the solution in the target environment.

Use Cases

- Developing a New Batch Application: Writing COBOL programs and JCL to create a new daily batch job for financial reporting or data processing.
- Enhancing an Online CICS Transaction: Modifying an existing CICS program to add new screens or business logic, followed by CICS resource definition updates.
- Implementing a DB2 Database Change: Creating new DB2 tables, indexes, or stored procedures, and updating DB2 application programs to utilize them.
- Upgrading a System Component: Applying PTFs (Program Temporary Fixes) or APARs (Authorized Program Analysis Reports) to a z/OS component or subsystem.
- Integrating with External Systems: Implementing z/OS Connect APIs or MQ message flows to enable data exchange between mainframe applications and distributed systems.

Related Concepts

Implementation is the crucial phase that follows System Design and precedes Production Support. It relies heavily on Programming Languages (COBOL, PL/I, Assembler) for logic, JCL for execution control, and Subsystems (CICS, DB2, IMS) as runtime environments. It is intrinsically linked with Software Configuration Management (SCM) for version control and Quality Assurance (QA) for ensuring the solution meets specifications and performs reliably before Deployment to the production z/OS environment.

Best Practices:

Adhere to SDLC: Follow a well-defined Software Development Life Cycle (SDLC) with clear phases for requirements, design, coding, testing, and deployment.
Leverage SCM Tools: Utilize robust Software Configuration Management tools (e.g., CA Endevor, IBM z/OS Change Tracker) for source code control, versioning, and promotion management.
Automate Testing: Implement automated unit and integration testing where feasible to ensure code quality and reduce manual effort.
Document Thoroughly: Maintain comprehensive documentation for design specifications, code comments, JCL procedures, and deployment instructions.
Plan for Rollback: Develop and test a clear rollback strategy to revert changes quickly and safely in case of unforeseen issues during production deployment.
Performance Tuning: Incorporate performance monitoring and tuning activities throughout the implementation process to optimize resource utilization and response times on z/OS.