Abend Handling

An abend is an abnormal end of a task. CICS assigns every abend a code that tells you exactly what went wrong - learning to read these codes is the core skill of CICS production support.

Types of abends

• Program check abends (ASRA) happen when the program does something the hardware forbids - bad addresses, bad data, divide by zero.
• Exceptional condition abends (AEI*) happen when a CICS command hits an unusual situation and no RESP option was coded - for example AEIM (NOTFND) or AEIS (NOTOPEN).
• Transaction abends (AICA runaway, AKCT timeout, AKC3 purge, ATCH deadlock, APCT program not found) describe task-level problems.
• When a task abends, CICS writes messages to MSGUSR, usually takes a dump, and backs out the task's unit of work.

Handling abends in the program

• The cheapest defense is the RESP option on every CICS command - it turns most exceptional conditions into testable return codes.
• EXEC CICS HANDLE CONDITION routes named conditions to error paragraphs without abending the task.
• EXEC CICS HANDLE ABEND catches any abend in the task and gives your program one last chance to clean up:-
  EXEC CICS
  HANDLE ABEND LABEL(9000-ABEND-PARA)
  END-EXEC.
  .
  .
  9000-ABEND-PARA.
  EXEC CICS SYNCPOINT ROLLBACK END-EXEC.
  MOVE 'Transaction failed. Please contact support.' TO MSGO.
  EXEC CICS
  SEND MAP('ERRMAP') MAPSET('ERRSET') ERASE
  END-EXEC.
  EXEC CICS RETURN END-EXEC.
• Keep the abend handler simple - it runs in a fragile state, so just roll back, inform the user and end cleanly.

Finding the cause of an abend

• Start with the abend code in the MSGUSR log or on the user's screen - it narrows the search immediately.
• Use CEDF (the execution diagnostic facility) to step through the program and watch each CICS command execute.
• For ASRA and storage problems, format the transaction dump with IPCS and look at the PSW and registers.