IBM AIX 7.2 – Common Problem 233 – Diagnosis and Fix

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

topas shows runqueue greater than CPU count and apps experience scheduling latency.

Environment & Reproduction

Triggered by undersized LPAR entitlement or runaway batch jobs and JVMs.

Root Cause Analysis

More runnable threads than virtual CPUs cause AIX to queue work in r in vmstat.

Quick Triage

Run vmstat 2 5 and topas to confirm sustained r > lcpu and high pc.

Step-by-Step Diagnosis

Use ps -eo pcpu,pid,args | sort -n and trprof to identify CPU-hungry processes.

Solution – Primary Fix

Increase LPAR entitled and virtual CPUs via HMC chhwres or DLPAR add of CPUs.

Solution – Alternative Approaches

Cap rogue processes with WLM classes or renice and schedo dispatcher tuning.

Verification & Acceptance Criteria

vmstat r averages below lcpu and topas pc stays under 0.9 during peak load.

Rollback Plan

Roll back DLPAR add with chhwres -r proc -o r and remove WLM classes if needed.

Prevention & Hardening

Right-size LPAR entitlement using nmon trends and alert when r > lcpu sustained.

Related Errors & Cross-Refs

Related to memory pressure, paging activity, and JFS2 latency under load.

Related tutorial: View the step-by-step tutorial for aix-7.2.

View all aix-7.2 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM AIX 7.2 Performance Management Guide on CPU and WLM.