IMPL - Implementation

Enhanced Definition

In the mainframe context, "implementation" refers to the comprehensive process of designing, coding, testing, and deploying a software solution, system modification, or new feature on an IBM z/OS platform. It encompasses all phases required to bring a conceptual requirement into a functional, operational state within the mainframe environment, often involving languages like COBOL, JCL, Assembler, and interaction with various IBM subsystems.

Key Characteristics

- Structured Lifecycle: Typically follows a formal System Development Life Cycle (SDLC), involving distinct phases such as requirements gathering, design, coding, unit testing, system testing, user acceptance testing (UAT), and production deployment.
- Resource Intensive: Requires significant allocation of mainframe resources, including CPU cycles for compilation and execution, DASD for datasets, and specialized skills from developers, system programmers, and operations staff.
- Rigorous Change Control: Operates under stringent change management processes due to the critical nature of mainframe applications, requiring formal approvals, version control (e.g., using SCM tools like CA Endevor or CA Panvalet), and detailed backout plans.
- Integration Focus: Mainframe implementations rarely occur in isolation; they almost always involve integration with existing legacy applications, databases (DB2, IMS DB), transaction managers (CICS, IMS TM), and batch processes.
- Performance and Reliability: A primary concern is ensuring the new or modified component meets stringent performance Service Level Agreements (SLAs) and maintains the high reliability and availability expected of z/OS systems.
- Extensive Testing: Involves multiple levels of testing, from developer unit tests (often using tools like XPEDITER) to comprehensive system and regression testing in dedicated test LPARs or environments.

Use Cases

- Developing New Business Applications: Implementing a new COBOL program to process customer orders, interact with a DB2 database, and generate regulatory reports.
- Enhancing Existing Systems: Modifying an existing CICS transaction to add new functionality, update screen layouts, or integrate with a new external service via MQSeries.
- Applying Vendor Software Updates: Implementing a new version of an IBM product (e.g., a new release of CICS TS or DB2 for z/OS) by applying PTFs/APARs, performing customization, and thorough testing.
- Batch Job Stream Modifications: Implementing changes to critical JCL procedures, adding new steps, modifying dataset allocations, or integrating new utility programs into a scheduled batch run.
- Security Policy Enforcement: Implementing new RACF rules, security exits, or auditing mechanisms to comply with updated corporate security policies or industry regulations.

Related Concepts

Implementation is the practical realization of designs created during the System Development Life Cycle (SDLC). It heavily relies on JCL for executing compilation, linking, and testing steps, and COBOL (or other languages like PL/I, Assembler) for the actual business logic. Successful implementation often involves careful interaction with CICS or IMS TM for online processing, and DB2 or IMS DB for data persistence, ensuring data integrity and transactional consistency. Software Configuration Management (SCM) systems are crucial for controlling the artifacts of implementation.

Best Practices:

Modular Design: Break down complex implementations into smaller, manageable, and testable modules to improve maintainability, facilitate parallel development, and reduce the risk of errors.
Thorough Testing: Conduct comprehensive unit, integration, system, and regression testing in dedicated test environments before promoting changes to production, utilizing tools like IBM Debug Tool or XPEDITER.
Version Control: Utilize robust Software Configuration Management (SCM) tools (e.g., CA Endevor, IBM Rational Team Concert) to manage source code, JCL, and other artifacts, ensuring traceability and facilitating rollbacks.
Documentation: Maintain clear and up-to-date documentation for all implemented components, including design specifications, program logic, JCL procedures, and operational instructions.
Performance Tuning: Design and implement with performance in mind, using tools like Omegamon or RMF to monitor and tune resource consumption (CPU, I/O, memory) during testing phases to meet SLAs.
Backout Planning: Always have a well-