Syntax:
RESET SLAVE [ALL]

RESET SLAVE makes the slave forget its replication position in the
master's binary log. This statement is meant to be used for a clean
start: It deletes the master.info and relay-log.info files, all the
relay log files, and starts a new relay log file. To use RESET SLAVE,
the slave replication threads must be stopped (use STOP SLAVE if
necessary).

*Note*: All relay log files are deleted, even if they have not been
completely executed by the slave SQL thread. (This is a condition
likely to exist on a replication slave if you have issued a STOP SLAVE
statement or if the slave is highly loaded.)

In MySQL 5.5 (unlike the case in MySQL 5.1 and earlier), RESET SLAVE
does not change any replication connection parameters such as master
host, master port, master user, or master password, which are retained
in memory. This means that START SLAVE can be issued without requiring
a CHANGE MASTER TO statement following RESET SLAVE.

In MySQL 5.5.16 and later, you can use RESET SLAVE ALL to reset these
connection parameters (Bug #11809016). Connection parameters are also
reset if the slave mysqld is shut down.

If the slave SQL thread was in the middle of replicating temporary
tables when it was stopped, and RESET SLAVE is issued, these replicated
temporary tables are deleted on the slave.

URL: http://dev.mysql.com/doc/refman/5.5/en/reset-slave.html

