How to Increase Max Connections in MySQL

Sometimes MySQL server may give “Too many connections” error message when you try to connect to a MySQL database. Here’s how to increase max connections in MySQL to fix this problem.


What causes MySQL Too Many Connections?

If you get “Too many connections” error message while connecting to MySQL database it means all available connections have been used by the various clients and your MySQL Server cannot open any new connections until any of the existing connections is closed.

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How Many Connections can MySQL handle?

By default, MySQL 5.5+ can handle up to 151 connections. This number is stored in server variable called max_connections. You can update max_connections variable to increase maximum supported connections in MySQL, provided your server has enough RAM to support the increased connections.

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How to Increase Max Connections in MySQL

Here are the steps to increase max connections in MySQL.


1. Check the default max connections

Log into MySQL command line tool and run the following command to get the current default max connections supported by your database server.

mysql> show variables like "max_connections";

You will see the following output.

+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 100   |
+-----------------+-------+

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2. Increase Max Connections

There are two ways to increase MySQL connections. Here’s the command to update max connections to 200 via MySQL command line tool without restart.

mysql> set global max_connections = 200;

The above command will increase max connections without restart but once the server is restarted, the changes will be gone. This method is useful to increase available connections in a production system such as a website/app, without having to restart your database server.

To permanently increase max connections, open my.cnf file,

$ sudo vi /etc/my.cnf

Depending on your Linux distribution and type of installation, my.cnf file may be located at any of the following locations.

  • /etc/my.cnf
  • /etc/mysql/my.cnf
  • $MYSQL_HOME/my.cnf
  • ~/.my.cnf

Add the following line under [mysqld] section.

max_connections = 200

Now if you restart MySQL server, the changes will persist.


3. Restart MySQL Server

Restart MySQL Server to apply changes

$ sudo service mysql restart

Hopefully, the above tutorial will help you increase max connections in MySQL.

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