What is ABEND?

ABEND is a technical term used in computing, especially in mainframe environments, to indicate that a program has stopped running unexpectedly due to a software bug, hardware malfunction, or system-level issue.

 Where is ABEND Used?

ABENDs are most commonly encountered in:

• Mainframe operating systems like IBM’s z/OS.
• Batch jobs, such as those written in COBOL, PL/I, or JCL.
• Transaction processing systems like CICS or IMS.
• Enterprise scheduling systems (e.g., CA-7, Control-M).

 Common Causes of ABENDs

1. Coding Errors
   • Null pointer references
   • Division by zero
   • Array index out of bounds
   • Invalid instructions
2. Input /Output Failures
   • Missing or corrupt input files
   • Invalid file formats
   • Permissions issues
3. Resource Limitations
   • Out of memory
   • Disk full
   • Stack overflow
4. System Failures
   • Hardware malfunction
   • Network timeout
   • Operating system crash

 Types of ABENDs

• User ABEND (Uxxxx): Triggered by application code, often with a specific error number.
  • Example: U4038 is common in COBOL programs when there’s an unhandled condition.
• System ABEND (Sxxxx): Triggered by the system due to hardware or OS issues.
  • Example: S0C7 indicates a data exception (e.g., trying to perform arithmetic on non-numeric data).

 Handling ABENDs

• Error Logging: Most systems generate a dump or log file showing the cause and memory state at the time of failure.
• Restart Logic: In batch systems, jobs may be restarted from the point of failure.
• Debugging Tools: Tools like IBM Fault Analyzer or IBM Debug Tool help trace and fix ABENDs.

 Example in Real Life

Imagine a payroll system that runs every Friday night as a batch job. If an input file with employee hours is missing or formatted incorrectly, the job might abend. This would stop the entire process, delaying payments until the issue is resolved.