Replication between servers in MySQL works through the use of the binary logging mechanism. The MySQL instance operating as the master (the source of the database changes) writes updates and changes to the database to the binary log. The information in the binary log is stored in different logging formats according to the database changes being recorded. Slaves are configured to read the binary log from the master and to execute the events in the binary log on the slave's local database.

The Master is dumb in this scenario. Once binary logging has been enabled, all statements are recorded in the binary log. Each slave will receive a copy of the entire contents of the binary log. It is the responsibility of the slave to decide which statements in the binary log should be executed; you cannot configure the master to log only certain events. If you do not specify otherwise, all events in the master binary log are executed on the slave. If required, you can configure the slave to only process events that apply to particular databases or tables.

Slaves keep a record of the binary log file and position within the log file that they have read and processed from the master. This means that multiple slaves can be connected to the master and executing different parts of the same binary log. Because the slaves control this process, individual slaves can be connected and disconnected from the server without affecting the master's operation. Also, because each slave remembers the position within the binary log, it is possible for slaves to be disconnected, reconnect and then 'catch up' by continuing from the recorded position.

Both the master and each slave must be configured with a unique id (using the server-id option). In addition, the slave must be configured with information about the master host name, log file name and position within that file. These details can be controlled from within a MySQL session using the CHANGE MASTER statement. The details are stored within the master.info file.

In this section the setup and configuration required for a replication environment is described, including step-by-step instructions for creating a new replication environment. The major components of this section are: