Problem with ORM by Weblogic

Hi all,

I create an EJB-Project which runs quite well in JBoss. Now I am going to deploy
it by Weblogic Express 10g. But I have problem by deploying. I got Exception as
follow:

Error processing persitence unit dwSpring2Jpa of module TestBEAEJB3Beans.jar:
Error looking up a DataSource for PersistenceUnit dwSpring2Jpa:
javax.naming.NameNotFoundException: Unable to resolve 'OracleDS'. Resolved '';
remaining name 'OracleDS'

My "persistence.xml" looks as follow:
<?xml version="1.0"?><persistence
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0"> <persistence-unit
name="dwSpring2Jpa">
<jta-data-source>OracleDS</jta-data-source> <properties>
<property name="hibernate.hbm2ddl.auto"
value="create-drop" /> </properties>
</persistence-unit></persistence>

My question: where should I locate the datasource descriptor which contains