OracleXADataSource cannot be cast to java.sql.Driver

Tried to start a Forms / Reports Server on an all new server. During startup of the AdminServer, I got an errormessage:

<BEA-000362> <Server failed. Reason: 

There are 1 nested errors:

oracle.security.jps.JpsException: oracle.security.jps.service.policystore.PolicyStoreException: javax.persistence.PersistenceException: java.lang.ClassCastException: oracle.jdbc.xa.client.OracleXADataSource cannot be cast to java.sql.Driver

Solution:

In my case it was quite simple: Start the Repository Database and the according listener process ... if not running. If running, check whether or not the Repository Database can be connected by using the EZConnect ConnectString for Your Repository DB. Pattern for EZConnect is like this: host.domain:port/servicename