anonymous wrote : 1)when I am using EJB3 Entities...do i require PP...? Yes, a persistence provider is required. EJB3 and JPA are not the same. A persistence provider follows the JPA spec. anonymous wrote : 2)if yes...how come my application ran without configuring a Persistence Provider(PP)...? JBoss internally uses Hibernate as the JPA Persistence provider, hence that's taken care of internally. Hmm, i was thinking this value was set globally at server level in JBOSS_HOME/server/< servername>/deployers/ejb3.deployer/META-INF/jpa-deployers-jboss-beans.xml, but i can't find it there. Anyway, if you are deploying in JBoss then the server will use Hibernate as the persistence provider. If you want to use some other persistence provider (like Toplink) then you will have to explicitly set that property in the persistence.xml anonymous wrote : 3) can I develop an application's Persistence layer using only JPA...? Yes anonymous wrote : | so where the difference is laying between the application developed using EJB3 Entities & the one developed using Hibernate JPA....???? EJB3 Entities == JPA Entities. And JPA entities are managed by JPA persistence providers - Hibernate is just one such provider which manages those EJB3/JPA entities. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4265182#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...