Investigate - Examining

Enhanced Definition

In the mainframe context, "investigate" or "examining" refers to the systematic process of analyzing system behavior, application execution, data states, or log records to identify the root causes of issues, understand performance characteristics, or verify operational integrity within the z/OS environment. It is a critical aspect of problem determination, debugging, and system optimization.

Key Characteristics

- Systematic Approach: Often involves a structured methodology, such as recreating issues, isolating variables, or following a predefined troubleshooting checklist.
- Tool-Dependent: Relies heavily on specialized mainframe utilities and software, including diagnostic tools (IPCS, Fault Analyzer), monitoring tools (OMEGAMON, RMF), and log analysis tools (SMF, SYSLOG).
- Data-Driven: Involves collecting and interpreting various forms of data, such as system dumps, trace records, log entries, performance metrics, and application output.
- Contextual Knowledge: Requires deep understanding of z/OS internals, specific applications (COBOL, PL/I, Assembler), middleware (CICS, DB2, IMS), and underlying infrastructure.
- Iterative Process: Often involves forming hypotheses, collecting data, analyzing findings, refining the hypothesis, and repeating the process until the root cause is identified.
- Multi-Domain: Can span across various layers of the enterprise computing stack, including hardware, operating system, network, storage, database, and application code.

Use Cases

- Application Abend Resolution: Diagnosing S0C4, S0C7, U-xxxx abends in COBOL, PL/I, or Assembler programs by analyzing dumps with IPCS or using Fault Analyzer.
- Performance Bottleneck Identification: Examining RMF reports, SMF data, or OMEGAMON metrics to pinpoint CPU, I/O, memory, or enqueue contention impacting system or application throughput.
- Data Integrity Verification: Investigating VSAM files, DB2 tables, or IMS databases after unexpected application behavior or suspected data corruption, often using utility programs or database query tools.
- Security Incident Analysis: Reviewing RACF audit trails, SMF records (type 80), and SYSLOG for unauthorized access attempts, privilege escalation, or suspicious system activity.
- JCL Error Debugging: Examining SYSOUT and SYSPRINT outputs, JES logs, and DD statements to understand why a batch job failed or produced incorrect results.

Related Concepts

Investigation is intrinsically linked to Problem Determination (PD), which is the overarching process of identifying the cause of a problem. It heavily utilizes Diagnostic Tools (e.g., IPCS for dump analysis, Fault Analyzer for abend analysis, Debug Tool for interactive debugging) and System Logs (SMF, SYSLOG, CICS logs, DB2 logs) as primary data sources. It is a fundamental skill for Application Developers (for debugging code), System Programmers (for z/OS issues), and Operations Staff (for production support and incident response).

Best Practices:

Document Symptoms Thoroughly: Record all observed symptoms, error messages, timestamps, and any steps taken immediately prior to the issue.
Reproduce the Issue (if safe): If possible and appropriate, try to consistently reproduce the problem in a controlled test environment to gather more specific diagnostic data.
Leverage Specialized Tools: Always use the most appropriate mainframe diagnostic tools for the task, rather than relying solely on generic methods.
Isolate the Problem: Systematically eliminate potential causes by narrowing down the scope, e.g., by testing components individually or simplifying the environment.
Check System Logs First: Prioritize reviewing relevant SYSLOG, SMF, CICS, DB2, or application-specific logs, as they often contain immediate clues or error messages.