I think you shall use this:
You should use the example in the middle because you want to
create a XADataSource and not a local-tx-datasource as you did.
No, that is a DB2 XA datasource, not an Oracle XA datasource. Please look at the following:
Note the line that says that there are example configurations in docs/examples/jca
A quick look at that directory will show you that there is indeed an oracle-xa-ds.xml file that shows you how to set up an Oracle XA Datasource.