The URL field must contain the host name or IP address and the port number (if necessary) of the Oracle server.
Use the next settings when the database type is Oracle:
Database type: Oracle 10.2 and later
URL: hostname:port_number
Database name: database name or SID
User name: user_name
Password: password
This is an example:
URL: 10.140.10.33:1521
Database name: XE
User name: testsuite
Password: ****
In the case above, Oracle Database Express Edition is used and the database name/SID is always XE. Are you sure that the database name in your case is 'Mendix' and not 'XE', 'ORA1' or whatever?
The Mendix Runtime connects to Oracle via the official JDBC drivers. On this page you see Data Source properties which are used when configure a JDBC Data Source. The Mendix URL field will be splitted by the ':' char. The left part is the Oracle serverName and the right part the Oracle portNumber.
Thanks a lot Jonathan, I tried your suggestion, and (just) adding the portnumber does the trick!