This is a project develope by other colleagues and have not used any transaction control machiname, and not use a unique method to handle database access. First I want to find a simple method to add transaction control, just as add 'for update' to the sql sentance. but it's not a fit solution. Now I use tyrex and jta to control the transaction and make a unqire method as dao to access the db. but rewrite lots of codes which need transaction control. Thanks for your answers.