IBM AIX 7.3 – Common Problem 106 – 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

Workload CPU bound while lparstat shows low %entc utilization.

Environment & Reproduction

Power LPAR with SMT-8 capable cores running legacy SMT-2.

Root Cause Analysis

smtctl setting limits hardware thread availability.

Quick Triage

smtctl shows current SMT mode and bound threads.

Step-by-Step Diagnosis

Compare with mpstat -s SMT thread usage per core.

Solution – Primary Fix

Set smtctl -m on -t 8 -w boot to enable SMT-8 persistently.

Solution – Alternative Approaches

Bind hot threads with bindprocessor if app is NUMA sensitive.

Verification & Acceptance Criteria

topas shows higher logical CPU usage and lower runqueue.

Rollback Plan

Revert with smtctl -m on -t 2 -w boot if regression seen.

Prevention & Hardening

Document SMT plan per workload (DB vs WAS).

Related Errors & Cross-Refs

Pairs with lparstat phantom interrupts when oversubscribed.

Related tutorial: View the step-by-step tutorial for aix-7.3.

View all aix-7.3 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM Docs: smtctl, lparstat, Power performance tuning.