Interrogate - Questioning

Enhanced Definition

In the mainframe context, "interrogate" refers to the act of querying, examining, or probing a system, subsystem, resource, program, or data store to retrieve information, ascertain status, or diagnose conditions. It is a fundamental process for monitoring, problem determination, and data retrieval within the z/OS environment.

Key Characteristics

- Tool-Dependent: Interrogation typically relies on specific z/OS commands, utility programs, debugging tools, or subsystem-specific interfaces (e.g., SDSF, CEMT, DB2 SPUFI, IMS DLI).
- Purpose-Driven: It is performed with a specific objective, such as checking job status, querying database contents, inspecting program variables, or verifying system resource availability.
- Interactive or Batch: Interrogation can be performed interactively via TSO/ISPF, CICS terminals, or console commands, or in a batch mode using JCL to execute utilities or programs.
- Diagnostic Focus: Frequently employed during problem determination, performance tuning, and security auditing to gather crucial evidence and understand system behavior.
- Real-time vs. Historical: Can involve examining current, active system states (real-time) or analyzing historical data from logs, dumps, or archived reports.

Use Cases

- Monitoring Batch Job Status: Using SDSF (System Display and Search Facility) to interrogate the status, output, and resource consumption of active or completed batch jobs.
- Querying Database Contents: Executing SQL queries against DB2 tables via SPUFI or QMF, or using DL/I calls to retrieve data from IMS databases.
- Debugging COBOL Programs: Employing a debugger like IBM Debug Tool to interrogate program variables, memory locations, and execution flow during testing or problem analysis.
- Checking CICS Transaction State: Using CEMT (CICS Master Terminal) commands or CICSPlex SM views to interrogate the status of CICS regions, transactions, tasks, and resources.
- System Resource Verification: Issuing z/OS console commands (e.g., D GRS, D U) to interrogate the status of enqueues, devices, storage, or address spaces.

Related Concepts

Interrogation is intrinsically linked to monitoring and debugging, serving as the primary mechanism for gathering the data required for these activities. It underpins system programming by providing the means to understand and control the operating environment. Furthermore, it is a core function in data management, enabling users and applications to retrieve and verify information stored in various mainframe data stores like VSAM, DB2, and IMS.

Best Practices:

Utilize Appropriate Tools: Select the most efficient and relevant tool for the specific interrogation task (e.g., SDSF for jobs, DB2 SPUFI for SQL, CEMT for CICS).
Understand Command Syntax and Impact: Be proficient in the syntax of z/OS commands and utility control statements, and understand the potential performance impact of extensive or poorly scoped queries.
Prioritize Security: Ensure proper authorization is in place before interrogating sensitive system areas, data, or user information, adhering to RACF or equivalent security policies.
Automate Routine Checks: Script common interrogation tasks using REXX, JCL, or automation products to proactively monitor system health and detect anomalies.
Document Findings: For complex problem determination or audit purposes, meticulously document the results of interrogations, including commands used, timestamps, and observed output.