🟠 High   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: SUSE Linux Enterprise Server 15

📖 ~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

Applications fail with `FATAL: sorry, too many clients already` during peak load.

Environment & Reproduction

Seen on database hosts that consolidated workloads or where pooling is disabled.

Root Cause Analysis

Connections from app servers exceed `max_connections` because no connection pooler is in place.

Quick Triage

Check current connections with `SELECT count(*) FROM pg_stat_activity;`.

Step-by-Step Diagnosis

Inspect `postgresql.conf` for `max_connections` and review `pg_stat_activity` states.

Illustrative mockup for sles-15 — postgres_connection-limit_terminal
Terminal diagnostics for PostgreSQL hits max_connections on SLES 15 — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Deploy pgbouncer in transaction pooling mode and point apps to it.

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Illustrative mockup for sles-15 — postgres_connection-limit_logs
Logs and evidence for PostgreSQL hits max_connections on SLES 15 — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Temporarily raise `max_connections` and tune `shared_buffers` to handle the surge.

Verification & Acceptance Criteria

Connection counts stay below 70% of `max_connections` and errors stop.

Rollback Plan

Roll back tuning changes via configuration backups if memory pressure spikes.

Prevention & Hardening

Standardise pooling for all production databases and monitor active sessions.

Pairs with high context-switch counts and idle-in-transaction sessions.

Related tutorial: View the step-by-step tutorial for sles-15.

View all sles-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

SUSE PostgreSQL packaging and pgbouncer integration notes.

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