Impact Analysis

Enhanced Definition

Impact Analysis, in the mainframe context, is the systematic process of identifying and evaluating the potential consequences and ripple effects of a proposed change to an application, system, data, or infrastructure component. It assesses what other components, programs, JCL, data structures, or subsystems might be affected by a specific modification, ensuring that all dependencies are understood before implementation. This process is crucial for minimizing risks, preventing outages, and ensuring the stability and integrity of critical z/OS environments. In the mainframe context, impact analysis is the systematic process of identifying and evaluating the potential consequences and ripple effects of a proposed change (e.g., code modification, system upgrade, data structure alteration) across interconnected applications, data, and infrastructure components within the z/OS environment. Its primary purpose is to understand the full scope of a change, mitigate risks, and ensure system stability and data integrity before implementation.

Key Characteristics

- Dependency Mapping: Involves tracing interdependencies between programs, copybooks, JCL, PROCs, data sets, databases (DB2, IMS), CICS transactions, security rules (RACF), and other system resources.
- Scope Definition: Can range from analyzing a single COBOL program modification to assessing the impact of a major operating system upgrade (e.g., z/OS new release) or a subsystem upgrade (e.g., CICS TS, DB2 for z/OS).
- Tool-Assisted: Often performed using specialized automated tools that parse source code, JCL, and configuration files to build a comprehensive dependency graph, significantly reducing manual effort and error.
- Risk Mitigation: Directly supports risk management by highlighting potential points of failure, performance degradation, or security vulnerabilities introduced by a change.
- Change Management Integration: A fundamental phase within the broader change management process, providing essential input for planning, testing, and deployment strategies.
- Version Control Awareness: Requires integration with Source Code Management (SCM) systems (e.g., Endevor, CA-Librarian, PDSMan) to analyze specific versions of components.

Use Cases

- COBOL Program Modification: When a requirement necessitates changing a COBOL program, impact analysis identifies all calling programs, called subroutines, copybooks, JCL members, CICS transactions, and DB2 tables or IMS segments that interact with the modified code.
- JCL Procedure Update: Assessing the effect of changing a shared JCL PROC (Procedure) used by multiple applications, identifying all jobs and job steps that might be affected by changes to DD statements, parameters, or utility steps.
- Database Schema Alteration: Analyzing the impact of adding a new column to a DB2 table or modifying an IMS segment, identifying all COBOL programs, CICS transactions, and batch jobs that access that specific table or segment.
- Applying a PTF/APAR: Evaluating the potential effects of installing an IBM Program Temporary Fix (PTF) or Authorized Program Analysis Report (APAR) on existing applications, especially if the fix modifies system exits or core components.
- System Software Upgrade: Planning for a major upgrade of CICS, DB2, IMS, or z/OS itself, where impact analysis helps identify applications that might require recompilation, re-linking, or modification due to API changes or new features.

Related Concepts

Impact Analysis is inextricably linked to Change Management, serving as its foundational planning step by providing the necessary intelligence to manage changes effectively. It heavily relies on Configuration Management and Source Code Management (SCM) systems, as these provide the definitive versions of components and their relationships. The output of impact analysis directly informs Testing Strategies, particularly Regression Testing, by identifying which test cases need to be executed to validate the change and ensure no unintended side effects. It also plays a role in Problem Management by helping to quickly identify the scope of a problem and potential fixes.

Best Practices:

Automate Where Possible: Leverage specialized mainframe impact analysis tools (e.g., IBM Application Discovery and Delivery Intelligence, Compuware Xpediter/File -AID, Broadcom CA-Vantage) to accurately and efficiently map dependencies across the entire ecosystem.
Define Clear Scope: Before initiating, clearly define the scope of the change and the boundaries of the analysis to prevent scope creep and ensure focus.
Involve Stakeholders: Engage application owners, system programmers, database administrators, and security specialists in the analysis process to gather comprehensive insights and validate findings.
Document Findings Thoroughly: Maintain detailed records of the analysis, including identified dependencies, potential risks, affected components, and recommended testing plans. This documentation is vital for audit trails and future reference.
Integrate with SCM: Ensure your impact analysis tools are tightly integrated with your SCM system to analyze the correct versions of source code and track changes effectively.
Perform Regularly: Conduct impact analysis not just for planned changes but also periodically to maintain an up-to-date understanding of system interdependencies, especially in evolving environments.