During replication the MySQL server creates a number of files that are used to hold the relayed binary log from the master, and record information about the current status and location within the relayed log. There are three file types used in the process:
The relay log consists of the events read from the binary log of the master. Events in this binary log are executed on the slave as part of the replication thread.
The master.info file contains the status and current configuration information for the slave's connectivity to the master. The file holds information on the master host name, login credentials, and the current position within the master's binary log.
The relay-log.info file holds the status information about the execution point within the slave's relay log files.
The relationship between the three files and the replication
process is as follows. The
retains the point within the master binary log that has been read
from the master. These read events are written to the relay log.
relay-log.info file records the position
within the relay log of the statements that have been executed.