AICA runaway task condition

AICA means a runaway task: a CICS transaction used too much CPU without returning control, so CICS killed it.

What it means

• CICS watches task CPU via DTIMOUT; a task that never yields looks like an infinite loop.
• It protects the region — one looping task must not stall everyone.

Common causes

• Genuine infinite loop in the application program.
• Loop exit condition that can never be met with certain input data.
• Very large file browse without yielding control periodically.

How to diagnose

• Check CSMT for AICA and identify the transaction and program.
• Review the program for loops; check the exit conditions against production data.
• Reproduce with the same input in a test region.

How to fix it

• Fix the loop termination logic.
• For long-running legitimate work, issue EXEC CICS SUSPEND or break work into chunks.
• Review DTIMOUT settings with the systems team if the workload is genuinely long.

Example: Guarantee loop termination

A safety counter turns an infinite loop into a detectable error.

Interview tip

• Q: How would you troubleshoot a AICA runaway task condition in production?
• A: I would identify the looping transaction from CSMT, review its loop exit conditions against the failing input, fix the termination logic, and consider periodic SUSPEND for long tasks.

Prevention checklist

• Code reviews focused on loop exits.
• Safety counters on unbounded loops.
• Test with production-scale data.