Divergence

Enhanced Definition

Divergence, in the mainframe context, refers to the state where components, configurations, data, or processes within a z/OS environment deviate from their intended, standardized, synchronized, or expected state. This deviation can occur between different environments (e.g., development vs. production), between replicated systems, or from established baselines. In the context of IBM mainframe systems, **divergence** refers to a state where a system component, configuration, data set, or process deviates from its intended, standardized, or expected state. This deviation can occur across different environments (e.g., development, test, production), between LPARs, or over time within a single environment, often leading to inconsistencies, unpredictable behavior, or operational issues.

Key Characteristics

- Unintended Variation: Represents an unplanned or unsynchronized difference from a defined standard or baseline.
- Scope: Can manifest in various forms, including source code, JCL, system parameters (SYS1.PARMLIB), application configurations (CICS, DB2, IMS), security rules (RACF), or data content.
- Detection Difficulty: Often subtle and challenging to detect without specialized comparison tools, robust change management, or automated auditing processes.
- Impact on Reliability: Can lead to unpredictable application behavior, performance inconsistencies, security vulnerabilities, operational errors, or failures during system recovery.
- Environmental Drift: Commonly observed as "environmental drift" where development, test, and production environments gradually become inconsistent over time.

Use Cases

- Code Synchronization: A COBOL program or JCL procedure in the production environment differs from the version in the source code management system (e.g., CA Endevor) or the version used in the test environment, leading to inconsistent application behavior.
- Configuration Management: A critical SYS1.PARMLIB member (e.g., IEASYSxx, PROGxx) or a CICS region parameter has been manually updated in one LPAR but not consistently applied to other LPARs in a sysplex or to the disaster recovery site.
- Data Replication: Data in a secondary DB2 subsystem or an IMS database, intended to be a synchronized replica of a primary system, shows inconsistencies due to replication failures or manual updates on the secondary.
- Security Profiles: RACF profiles or resource rules for a specific application or user group are not identical across multiple z/OS instances, potentially creating security gaps or access issues.
- Operational Procedures: Batch job schedules or operational scripts used for system maintenance vary between shifts or teams, resulting in inconsistent execution or missed steps.

Related Concepts

Divergence is a critical concern for Change Management and Configuration Management on z/OS, as it directly undermines the integrity and predictability these disciplines aim to achieve. It highlights the importance of robust Source Code Management (SCM) systems like CA Endevor or IBM Engineering Workflow Management (EWM) for version control. It is closely related to System Synchronization and Disaster Recovery (DR), where maintaining identical configurations and data across primary and backup sites is paramount. Effective Auditing and Compliance efforts often involve identifying and remediating divergences.

Best Practices:

Implement Robust SCM: Utilize a centralized Source Code Management system (e.g., CA Endevor, Git for z/OS) for all source code, JCL, and configuration files to ensure version control and controlled promotion.
Automate Configuration Deployment: Employ automation tools and scripts to deploy system parameters, application configurations, and security rules consistently across all environments, reducing manual error.
Regularly Audit and Compare: Schedule regular automated comparisons of critical system files, configurations, and security profiles between environments (e.g., DEV vs. PROD, Primary vs. DR) to detect and report divergences promptly.
Establish Strict Change Control: Enforce formal change control procedures requiring approvals, documentation, and verification for all modifications to production systems and configurations.
Utilize Comparison Tools: Leverage specialized mainframe comparison utilities (e.g., ISPF SuperC, third-party tools) to identify differences in datasets, PDS members, or configuration files.