cant i look up datasource connection using environment variables

[maha laxmi]

as i said in my previous post we are migrating from oracle app server to jboss4.0.3;

in the existing beans(EJB) we used to look up for datasource connection ctx.lookUp("java:comp/env/jdbc/DB");

when i deploy existing ejb's in jboss i am getting NamingnotFound Exception when i look up datasource connection;but when i look up like this ctx.lookUp("java:jdbc/DB");i am getting database connection.

in oracle-ds.xml i mentioned JNDI name as jdbc/DB;

in jboss.xml also i metioned <res-ref-name>jdbc/DB</res-ref-name>
<resource-name>jdbc/DB</resource-name>

in all our existing beans we used look up ctx.lookUp("java:comp/env/jdbc/DB") like this;

should i change all beans to like this ctx.lookUp("java:jdbc/DB");