Does EJB3 have mechanism that solve's DMBS portability issues? (so my app's code work with Oracle and SQL Server with no DBMS specific SQL statements, for example). I heard Hibernate does that, and i also heard both technologies(EJB3 and Hibernate) are similar.
Carlos, If you don't use DB specific SQL, it is portable. This is true regardless of technology (pure JDBC, EJB, Hibernate, etc.) It is also possible to write non-portable code using any technology. For example native queries in JPA.
Note that EJB 3 is JPA for the entity beans part. And Hibernate is an implementation of JPA.