Creating a new user or modifying any existing user through MDM GUI may cause a Remote excpetion error with Websphere application server as below.

JAV-8012: Exception (REMOTE EXCEPTION) occurred. Program error or application not installed/configured correctly or application unstable. Contact customer support. Additional information: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.MarshalException: CORBA MARSHAL 0x4942f8b1 No; nested exception is: org.omg.CORBA.MARSHAL: com.tibco.mdm.directory.security.role.RoleAssignmentElement is not Serializable and not Externalizable vmcid: IBM minor code: 8B1 completed: No, Unknown.

The excpetion is related to Websphere application server configuration where ORB(Object Request Broker) settings were missed and results this error.

Below are the steps to configure the ORB Service details through Websphere admin console.

1) Login into Websphere Admin Console and choose the Container Settings.
2) Expand Container Services and click the ORB service link.The Configuration tab is displayed. 
3) Under General Properties, check the Pass by reference check box. 
4) Click OK. A message is displayed with the Save and Review options. 
5) Click the Save link to save changes to the master configuration.

After a server(Websphere) restart,we will be able to create a new user or modify any existing users within MDM enterprise.