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Interactive Problem Control System - IPCS debugging

Enhanced Definition

IPCS (Interactive Problem Control System) is a core z/OS component that provides an interactive, command-driven environment for analyzing system and program dumps. Its primary purpose is to assist system programmers and application developers in diagnosing the root cause of system failures, program abends, and performance issues by examining the state of the system at the time the dump was taken.

Key Characteristics

- Comprehensive Dump Analysis: IPCS can process various types of z/OS dumps, including SVC dumps, SYSMDUMPs, standalone dumps, CICS transaction dumps, and DB2 dumps, allowing for in-depth post-mortem analysis of system and application states.
- Interactive Command-Driven Interface: Users interact with IPCS through a command-line interface, typically accessed via TSO/ISPF, executing commands to display, format, and analyze data within the dump.
- Symbolic Resolution: It provides robust capabilities to symbolically resolve memory addresses to program names, module entry points, data areas, and control block fields, making the raw hexadecimal dump data understandable.
- Control Block Formatting: IPCS offers extensive functionality to format and display z/OS control blocks (e.g., TCB, ASCB, SSCVT, RTM2) in a human-readable structure, revealing critical system status and resource allocation details.
- Extensibility: Users can extend IPCS functionality by writing custom VERB routines (often in assembler or PL/X) or exit routines to format proprietary control blocks or perform specialized analysis tailored to specific applications or subsystems.
- Data Manipulation and Search: It allows users to read, search for specific data patterns, and temporarily modify (within the IPCS session) data within the dump's memory image to test hypotheses.

Use Cases

- Diagnosing Program Abends: Analyzing SVC dumps generated from application abends (e.g., S0C4, S0C7, S0CB) to pinpoint the exact instruction, data corruption, or logic error that caused the failure.
- Investigating System Hangs/Loops: Examining standalone or SVC dumps taken during a system hang or loop condition to identify the blocked resources, looping programs, or deadlocks that led to the system's unresponsiveness.
- Root Cause Analysis for CICS/DB2 Issues: Using IPCS to analyze CICS transaction dumps or DB2 dumps to diagnose issues like storage violations, resource contention, or