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ABEND - Abnormal End of Task

Enhanced Definition

An ABEND (Abnormal End) signifies the unplanned termination of a program, task, or job on an IBM z/OS system due to an error condition. It indicates that the program could not complete its intended processing successfully and was forced to stop.

Key Characteristics

- Unplanned Termination: An ABEND is an unexpected halt, unlike a normal program exit, which typically completes with a successful return code.
- Associated with a Completion Code: Every ABEND is identified by a unique hexadecimal completion code, which can be a System ABEND code (e.g., S0C7 for data exception, S0B1 for I/O error) or a User ABEND code (e.g., U1000, U4000), often issued by application programs or subsystems.
- Generates a Dump: Typically, an ABEND triggers the creation of a dump (e.g., SVC dump, transaction dump, SYSMDUMP, SYSUDUMP) containing the contents of memory, registers, and control blocks at the time of the error, crucial for debugging.
- Impacts Job/Task Status: A job experiencing an ABEND will typically terminate with a JCL condition code indicating failure, and its output (SYSOUT) will contain messages related to the ABEND.
- Can be Intercepted/Handled: In some environments (like CICS or IMS), or within application code using specific language constructs (e.g., ON SIZE ERROR in COBOL, ESTAE macros in assembler), ABENDs can be intercepted or partially handled to perform cleanup or provide more graceful recovery.

Use Cases

- Debugging COBOL Batch Programs: When a COBOL program encounters a data exception (S0C7), an array out of bounds, or an unhandled file I/O error, it results in an ABEND, requiring analysis of the job log and dump.
- Identifying JCL Errors: An ABEND can occur if JCL specifies an invalid dataset name, an incorrect DD statement, or insufficient region size (S80A, S222), indicating a configuration or resource issue.
- CICS Transaction Failures: A CICS transaction might ABEND (e.g., ASRA for program check, APCT for program not found) due to application logic errors, resource contention, or invalid data access, requiring `C