UNLOCK TABLES explicitly releases any table locks held by the
current session. See
LOCK TABLES for more information.
In addition to releasing table locks acquired by the
LOCK TABLES statement, the
UNLOCK TABLES statement also releases the global read lock acquired by the
FLUSH TABLES WITH READ LOCK statement. The
FLUSH TABLES WITH READ LOCK statement is very useful for performing backups. See
FLUSH for more information about
FLUSH TABLES WITH READ LOCK.