IBM AIX 7.2 – Common Problem 104 – 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 sustained Wait% above 40 and applications stall on I/O.

Environment & Reproduction

AIX 7.2 database or batch workload on SAN-attached storage.

Root Cause Analysis

Disk queue depths saturate and threads block in IOWAIT state.

Quick Triage

Open topas, press ‘D’ for disks and ‘P’ for processes to spot the source.

Step-by-Step Diagnosis

Capture iostat -DRTl 5 5 and filemon -O lf,lv,pv -o /tmp/fm.out for detail.

Solution – Primary Fix

Increase hdisk queue_depth with chdev -l hdiskN -a queue_depth=32 -P then reboot.

Solution – Alternative Approaches

Spread I/O across more hdisks by adding paths or LVs with mklv -e x.

Verification & Acceptance Criteria

iostat shows %tm_act balanced and Wait% under 15 during the same workload.

Rollback Plan

Restore previous queue_depth with chdev -P if performance regresses.

Prevention & Hardening

Right-size queue_depth from vendor guidance and monitor with nmon -f.

Related Errors & Cross-Refs

Pairs with high svc_t in iostat and run-queue spikes in vmstat.

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 Docs: iostat, filemon, topas, hdisk queue tuning.