Never tried this, but have a look in the file $JBOSS_HOME/server/default/conf/standardjbosscmp-jdbc.xml
and you will find that there are already defined Oracle9i, Oracle8, Oracle7 type-mappings (as well as "Hypersonic SQL"). Maybe if you use one of those names instead of just "Oracle" ?
You're legend! It works!
I am facing lot of problems getting Oracle datasource configured on JBoss 3.0.4.
Could you please send me the steps you followed to get the same done at your end.
Thanks in advance.