MySQL DB engine with transactions, foreign keys and other technologies support.
Transaction support within the database is pretty much required since RT 3.0.0 and up. updating from earlier versions does not update the table engine from MyISAM to InnoDB automatically. Earlier versions of 3.0.0 did run (buggily) without InnoDB, but the transaction roll-back support is central nowadays. You might want look into the ''ALTER TABLE'' syntax for MySQL to change the table engine.