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PostgreSQL Glossary

LSN (Log Sequence Number)

A byte position in the WAL stream that uniquely identifies a point in time for recovery or replication. Example: pg_last_wal_replay_lsn() shows the last r…

Definition

A byte position in the WAL stream that uniquely identifies a point in time for recovery or replication.

What LSN (Log Sequence Number) Means in PostgreSQL

A byte position in the WAL stream that uniquely identifies a point in time for recovery or replication.

LSN (Log Sequence Number) appears frequently in production operations, architecture decisions, and troubleshooting workflows. Understanding this term helps teams reason about reliability, performance, and safe change management.

Why LSN (Log Sequence Number) Matters

Teams that understand LSN (Log Sequence Number) can make better decisions on database design, incident response, and release safety.

In modern PostgreSQL environments, this concept often connects directly to backup strategy, performance tuning, and operational confidence.

  • Improves decision quality for production operations
  • Reduces avoidable troubleshooting time
  • Strengthens reliability and recovery planning

Practical Example

pg_last_wal_replay_lsn() shows the last replayed LSN on a standby; useful for monitoring lag.

Where To Learn More

You can explore deeper implementation patterns in the Vela articles library, review platform workflows in How Vela Works, and compare approaches in our PostgreSQL comparisons.

Related Glossary Topics

Lock Logical Replication ACID Atomicity Archiving (WAL Archiving) archive_command archive_mode BYOC (Bring Your Own Cloud)

Frequently Asked Questions

What is LSN (Log Sequence Number) in PostgreSQL?
A byte position in the WAL stream that uniquely identifies a point in time for recovery or replication.
Why is LSN (Log Sequence Number) important?
LSN (Log Sequence Number) matters because it directly affects how teams build, operate, and recover PostgreSQL systems in production.
Can you give a practical LSN (Log Sequence Number) example?
pg_last_wal_replay_lsn() shows the last replayed LSN on a standby; useful for monitoring lag.
How does LSN (Log Sequence Number) relate to backup, recovery, or performance?
In most production deployments, LSN (Log Sequence Number) influences one or more of these areas: data safety, restore behavior, and performance under load.
What should teams check first when implementing LSN (Log Sequence Number)?
Start with clear operational goals, test in a non-production environment, and validate behavior with repeatable runbooks before relying on it in production.