I found the problem , we should use exact file oracle-xa-ds.xml format as specified in jboss-as/docs/examples/jca directory .
When I was missing
I was getting NoClassFoundError , but as soon as i added metadata type mapping then it worked fine.
I guess jboss should have given some better error message instead of failing in NoClassFoundError , weird.
I used metadata with Oracle 11g and it worked fine.
Thanks