Cause: Only users IDENTIFIED GLOBALLY
may use a privileged database link.
Action: Either change the user to a
global user or try to use a different database link.

Relared Errors:
ORA-28028:
could not authenticate remote server
ORA-28029:
could not authorize remote server for user string
ORA-28030:
Server encountered problems accessing LDAP directory service
ORA-28031:
maximum of string enabled roles exceeded
ORA-28035:
Cannot Get Session Key for Authentication
ORA-28037:
Cannot Get Session Key for RACF Authentication
ORA-28038:
disallow O2LOGON
ORA-28039:
cannot validate Kerberos service ticket
ORA-28040: No
matching authentication protocol
ORA-28041:
Authentication protocol internal error