IBM AIX 7.2 – Common Problem 155 – 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

Database response time degrades sharply during peak hours. Users report timeouts and topas shows sustained paging-space activity above acceptable thresholds.

Environment & Reproduction

Seen on LPARs where memory is overcommitted or vmo tuning has drifted from baseline.

vmstat 2 5
oslevel -s
uname -a

Root Cause Analysis

Cause is typically undersized real memory, computational pages spilling to paging space, or vmo parameters such as minperm/maxperm out of recommended bands.

Quick Triage

Capture vmstat and topas data to confirm computational versus file page pressure.

vmstat 2 5

Step-by-Step Diagnosis

Capture deeper evidence to isolate the failure path.

vmstat 2 5
topas -P
svmon -G
lsps -a
vmo -L minperm%

Solution – Primary Fix

Apply the proven primary fix in a controlled change window.

vmo -p -o lru_file_repage=0
vmo -p -o minperm%=3
vmo -p -o maxperm%=90
chps -s 2 paging00

Solution – Alternative Approaches

Use these alternatives when the primary fix is blocked by environmental constraints.

lparstat -i
dlpar -m add 4096 -p $(hostname)
mkps -s 2 -n rootvg

Verification & Acceptance Criteria

Confirm the system meets acceptance criteria after the change.

vmstat 5 5
svmon -G
lsps -a
topas

Rollback Plan

Revert cleanly if regressions appear during validation.

vmo -d minperm%
vmo -d maxperm%
chps -d 1 paging00

Prevention & Hardening

Reduce recurrence with monitoring and preventive tuning.

tuncheck -f /etc/tunables/lastboot
topasrec -L -s 60 -R 1 -o /var/perf/topas.log
nmon -f -s 60 -c 60

Related Errors & Cross-Refs

Related to JFS2 cache pressure, AIO server shortage, and CPU folding limiting scheduling responsiveness.

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, vmo man page, IBM Power tuning whitepapers.