We are trying to migrate from Jboss 3.2.3 to Jboss 4.0.4. We carried out a small POC and the results suggest we are definitely in dark about some key concepts. My concerns are: 1.We are currently using EJB 2.0. We encountered problems on passing objects which were not serialized. Is it mandatory to have all the support classes implement serializable? Is there any way to overcome as we see it as a performance overhead? 2.What is the significance of passbyvalue tag in ear-deployer.xml and jboss-service.xml? Heard someone is saying it must be marked true in both these xml files if we are using remote beans. Will appreciate any help.