Feedback - Response Information

Enhanced Definition

In the mainframe context, "Feedback - Response Information" refers to the various codes, messages, and diagnostic data generated by z/OS, batch jobs, online transactions, utilities, and system components to indicate the status, outcome, or any issues encountered during their execution. This information is crucial for monitoring, debugging, and ensuring the successful operation of mainframe applications and systems.

Key Characteristics

- Standardized Codes: Often represented by numeric return codes (RC=0, RC=4, RC=8), condition codes, or abend codes (e.g., S0C4, U4000), which provide a quick status indicator.
- Descriptive Messages: Accompanied by textual messages (e.g., IEF285I, IDCAMS SYSTEM SERVICES, DFHAC2206) that provide more detailed context about the event or error.
- Diagnostic Data: Can include various types of dumps (e.g., SVC dump, transaction dump, system dump), trace entries, and log records that capture the system's state at the time of an event.
- Hierarchical Nature: Feedback can originate at multiple levels, from individual program statements, through utility steps, job steps, and up to the entire job or system.
- Programmatic Access: Many feedback mechanisms (like return codes) are accessible programmatically (e.g., in COBOL via the RETURN-CODE special register, or in JCL via the COND parameter).
- Persistent Records: Typically written to job logs (SYSOUT), system logs (SYSLOG), or specific dataset logs for later review, auditing, and problem determination.

Use Cases

- Job Monitoring and Control: JCL uses COND parameters to evaluate return codes from previous steps, determining whether subsequent steps should execute based on success or failure.
- Error Handling and Debugging: Developers use abend codes, system messages, and dumps to diagnose program failures, data integrity issues, or resource contention in COBOL, PL/I, or Assembler programs.
- System Automation: Automation tools and scripts parse job logs and system messages to trigger alerts, restart failed processes, or initiate recovery procedures for critical applications.
- Performance Tuning: Analyzing performance-related messages (e.g., from DB2, CICS, IMS) helps identify bottlenecks and optimize resource utilization for improved throughput.
- Auditing and Compliance: Logged feedback provides an audit trail of system events, job executions, and transaction outcomes, essential for regulatory compliance and security reviews.

Related Concepts

Feedback information is intrinsically linked to JCL (Job Control Language) through COND parameters and job logs, COBOL programs via the RETURN-CODE special register and DISPLAY statements, and CICS, DB2, and IMS through their respective message logs and diagnostic facilities. It forms the basis for System Automation and Workload Management, enabling automated responses to system events. It is also critical for Problem Determination and Change Management, as understanding feedback is essential for validating changes and resolving issues across the z/OS ecosystem.

Best Practices:

Standardize Return Codes: Establish clear conventions for application return codes (e.g., 0 for success, 4 for warning, 8+ for errors) to ensure consistent and easy interpretation across applications.
Log Essential Information: Ensure that critical feedback, especially error messages and diagnostic data, is consistently logged to accessible locations (e.g., SYSOUT, SYSLOG, application-specific logs).
Implement Robust Error Handling: Design applications (COBOL, PL/I) to anticipate potential errors and provide meaningful, specific feedback, rather than relying solely on generic system abends.
Automate Monitoring and Alerting: Utilize system automation tools to monitor key feedback (e.g., high return codes, specific abend messages) and trigger alerts for operational staff.
Regularly Review Logs: Periodically review job logs, system logs, and application logs to proactively identify recurring issues, performance degradation, or potential security concerns.
Provide Contextual Dumps: Configure dumps (e.g., SYSUDUMP, SYSMDUMP) to be generated only when specific abends or conditions occur, providing focused diagnostic data without excessive overhead.