IBM AIX 7.2 – Common Problem 022 – 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 wa% over 30 and applications block on disk I/O.

Environment & Reproduction

IBM AIX 7.2 LPAR exhibiting topas / nmon high I/O wait issues under standard PowerVM workloads.

topas -P
iostat -aD 2 5

Root Cause Analysis

Slow SAN response time or hot LV without spreading causes wait.

Quick Triage

Confirm scope with errpt, recent changes, and subsystem state via lssrc.

iostat -aD 2 5
filemon -O all -o /tmp/fmon.out

Step-by-Step Diagnosis

Run filemon to identify hot LVs and PVs driving wait.

filemon -O lf,lv,pv -o /tmp/fmon.out
trcrpt /tmp/fmon.out

Solution – Primary Fix

Spread the hot LV across more PVs or migrate to faster tier.

reorgvg datavg lv01
migratepv hdisk5 hdisk9 lv01

Solution – Alternative Approaches

Adjust queue_depth on hdisks and enable read_cache.

Verification & Acceptance Criteria

Confirm subsystem returns to RUNNING state and errpt shows no new entries.

iostat -aD 2 5
filemon -O all

Rollback Plan

Restore prior configuration from mksysb or alt_disk_install clone if the fix regresses.

reorgvg datavg  # revert if hotspots shift

Prevention & Hardening

Encode the fix in NIM customisation scripts and monitor via topas/nmon.

chdev -l hdisk5 -a queue_depth=32 -P

Related Errors & Cross-Refs

high iostat svc time; SAN slow drain

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

AIX Performance Tuning – Storage