First obvious point, It won't understand DS.xml it has to end with -ds.xml, e.g. oracle-xa-ds.xml
Second, you know it is bound at java:/OracleXaDS?
There should be a message on the console saying where it is bound.
After that, what are the error messages in the log?
If you are having trouble finding them, try:
$ touch $JBOSS_DIST/server/xxx/deploy/oracle-xa-ds.xml
to redeploy it.
Also look at docs/examples/jca or this:
You need to set certain parameters because of "broken" behaviour in the Oracle driver,
but that shouldn't stop it binding into JNDI.