skip-lock-tables and mysqldump

Question

Daily we run mysql dumps on about 50 individual databases, package them up and then store them offsite. Some of these databases are rather large and contain myisam tables (which

Answer 1

--skip-lock-tables parameter instructs the mysqldump utility not to issue a LOCK TABLES command before obtaining the dump which will acquire a READ lock on every table. All tables in the database should be locked, for improved consistency in case of a backup procedure. Even with skip-lock-tables, while a table is dumped, will not receive any INSERTs or UPDATEs whatsoever, as it will be locked due the SELECT required to obtain all records from the table. It looks like this

SELECT SQL_NO_CACHE * FROM my_large_table

and you can see it in the process list with the SHOW PROCESSLIST command. If you are using the MyISAM engine which is non-transactional, locking the tables will not guarantee referential integrity and data consistency in any case, I personally use the --skip-lock-tables parameter almost always. In InnoDB use the --single-transaction parameter for the expected effect. Hope this helps.