MySQL Server (version 3.23-max and all versions 4.0 and above) supports 
transactions with the InnoDB and BDB transactional storage engines. InnoDB 
provides full ACID compliance.

The other nontransactional storage engines in MySQL Server (such as MyISAM) 
follow a different paradigm for data integrity called “atomic operations.” 
In transactional terms, MyISAM tables effectively always operate in 
autocommit = 1 mode. Atomic operations often offer comparable integrity with 
higher performance.

http://dev.mysql.com/doc/refman/5.0/en/ansi-diff-transactions.html

P.S. zodziu darinys "comparable integrity", tiesa sakant, siek tiek sukelia 
sypsena... panasiai kaip "truputi nescia" :)