IBM AIX 7.3 – Common Problem 236 – 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

fcstat reports rising LINK FAILURE, LOSS OF SYNC, or INVALID CRC counters on fcsN.

Environment & Reproduction

Seen with dirty SFPs, failing fiber cables, or unstable SAN fabric ports.

Root Cause Analysis

Physical layer issues corrupt frames; AIX retries cause I/O latency and PERM disk errors.

Quick Triage

Run fcstat fcs0 and errpt -j FFFFFFFF | head to view trend and recent events.

Step-by-Step Diagnosis

Use lsdev -Cc adapter and lsattr -El fcs0 to confirm topology, then check SAN switch port counters.

Solution – Primary Fix

Clean SFPs, replace suspect fibers, and re-run fcstat to confirm counters stop rising.

Solution – Alternative Approaches

Migrate the workload to a redundant fabric path with chpath while replacing hardware.

Verification & Acceptance Criteria

fcstat shows zero new errors after 24h and disk error rate returns to baseline.

Rollback Plan

If a new SFP causes regressions, revert and engage SAN vendor before resuming.

Prevention & Hardening

Schedule SFP cleaning windows and trend fcstat metrics into nmon or PCM.

Related Errors & Cross-Refs

Related to LVM stale PPs and SAN multipath PCM events.

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 AIX 7.3 fcstat command reference and SAN troubleshooting guide.