This is a command-line option for the
Stop slave SQL thread and wait to start backup until Slave_open_temp_tables in "SHOW STATUS" is zero. If there are no open temporary tables, the backup will take place, otherwise the SQL thread will be started and stopped until there are no open temporary tables. The backup will fail if Slave_open_temp_tables does not become zero after --safe-slave-backup-timeout seconds. The slave SQL thread will be restarted when the backup finishes.