Save it. Redeploy and see how that goes. The above file is simplified version. What it means is, just refer already deployed data source whose jndi name is "jdbc/mydbDSDS". If you really have some extra properties, you can retain them. Otherwise they are not required.
<persistence-unit name="mydbDS"> <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider> <jta-data-source>jdbc/mydbDSDS</jta-data-source> <properties> <property name="eclipselink.target-server" value="WebLogic_10"/> <property name="eclipselink.cache.shared.default" value="false"/> </properties> </persistence-unit> </persistence>