EJB 3.0 Persistence Specification, Section 6.2 wrote : A persistence unit is defined by a persistence.xml file. The jar file or directory whose META-INF | directory contains the persistence.xml file is termed the root of the persistence unit. In Java EE, the root of a persistence unit may be one of the following: | | * an EJB-JAR file | * the WEB-INF/classes directory of a WAR file[40] | * a jar file in the WEB-INF/lib directory of a WAR file | * a jar file in the root of the EAR | * a jar file in the EAR library directory | * an application client jar file S, ALR View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4195688#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...