and "http://docs.oracle.com/cd/E21764_01/web.1111/e13737/oracle_rac.htm#CHDHHCAJ" Please advice
What is your remaining question?
The PDF documentation is old and broken. the other doc is newer, and clearer but not exact.
"Additional Considerations When Using WebLogic Server with Oracle RAC
Dynamic Transaction Processing (DTP) is not supported to coordinate transactions when using GridLink Data Sources or multi data sources with Oracle RAC."
With either GridLink or MultiDatasources, WebLogic allows the use of the whole
cluster to do XA, not needing the limitation of a DTP service running only on one node.