PostgreSQL Reload vs Restart

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• 18 Oct, 2025
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PostgreSQL Reload vs Restart

Introduction

PostgreSQL reload vs restart

When managing a PostgreSQL database, DBAs often need to apply configuration changes.
But not all changes require a full database restart. Some can be applied instantly using a simple reload.

So, what’s the difference between PostgreSQL Reload vs Restart, and when should you use each?
Let’s break it down. 👇

Understanding PostgreSQL Configuration Files

PostgreSQL configuration parameters are stored in:

• postgresql.conf – main configuration file

• pg_hba.conf – client authentication settings

• pg_ident.conf – user mapping for authentication

When you modify these files, PostgreSQL needs to re-read them — either via reload or restart.

What is a Reload?

A reload means PostgreSQL re-reads its configuration files without stopping or restarting the server.
Running sessions stay active, and there’s no downtime.

You can trigger a reload in several ways:

pg_ctl reload
# or
SELECT pg_reload_conf();
# or
sudo systemctl reload postgresql

✅ Reload applies changes to:

• Logging (log_min_duration_statement, etc.)

• Autovacuum settings

• Planner options

• Statement timeout values

🚫 Reload does NOT apply changes to:

• shared_buffers

• max_connections

• wal_level
  (these require a restart)

 What is a Restart?

A restart means the PostgreSQL server process stops and then starts again.
All active connections are closed temporarily — resulting in brief downtime.

Command examples:

pg_ctl restart
# or
sudo systemctl restart postgresql

✅ Restart is required when:

• Changing memory parameters (shared_buffers, work_mem)

• Modifying WAL parameters (wal_level, max_wal_size)

• Adjusting connection limits (max_connections)

• Enabling/disabling extensions that affect system startup

When to Use Reload vs Restart