Well, as I said, instead of using transaction-type JTA, I'm using RESOURCE_LOCAL and a non-jta-data-source. I think it's something about the security, the transaction manager of hibernate (which is the persistence provider for JBoss) cannot join with the JTA, which is managed by JBoss, and the Database Server's own transaction manager. Anyway, changing to RESOURCE_LOCAL and non-jta-data-source may help, but be sure to provide the right hibernate.dialect property in persistence.xml. In my case, I used SQL Server, so my properties elements in persistence.xml should look like this: | <properties> | <property name="hibernate.dialect" | value="org.hibernate.dialect.SQLServerDialect" /> | <property name="hibernate.hbm2ddl.auto" value="update" /> | </properties> | For your right dialect, please have a look at hibernate project's website. About the property hibernate.hbm2ddl.auto, which value is update, it means that if there're any changes in the Entity Bean, update those changes to the database. It can have other values, once again, you should refer to the documents of hibernate. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4141805#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...