Fix Connection Pool Full in PostgreSQL: Database Error Solution (2026)
How to Fix “Connection Pool Full” in PostgreSQL (2026 Guide) The Short Answer To fix the “Connection Pool Full” error in PostgreSQL, increase the connection pool size by editing the postgresql.conf file or by using the ALTER SYSTEM command. For example, you can increase the pool size from the default 100 to 200 by running the command ALTER SYSTEM SET max_connections = 200;. Why This Error Happens Reason 1: The most common cause of the “Connection Pool Full” error is when the number of concurrent connections to the database exceeds the configured maximum connection limit, which is 100 by default. This can happen when multiple applications or users are accessing the database simultaneously. Reason 2: An edge case cause of this error is when a connection is not properly closed, causing it to remain idle and occupy a connection slot. This can happen due to poor application design or network issues. Impact: When the connection pool is full, any new connection attempts will result in a “Connection Pool Full” error, leading to a database error and potentially causing application downtime. Step-by-Step Solutions Method 1: The Quick Fix Go to Settings > postgresql.conf (usually located at /etc/postgresql/common/postgresql.conf or ~/.postgresql.conf) Edit the max_connections parameter to increase the connection pool size, for example, max_connections = 200 Restart the PostgreSQL service by running the command sudo service postgresql restart or pg_ctl restart Method 2: The Command Line/Advanced Fix You can also use the ALTER SYSTEM command to increase the connection pool size. For example: ...