Cause: During the course of opening a
privileged database link, the remote server was found to lack the necessary
authorizations to connect as the current global user. This may be because the
server was not authorized by the network security service. Or it may be
because the local server is restricting access by the remote server using the
DBMS_SECURITY_DOMAINS_ADMIN package.
Action: Grant the remote server the
proper authorization to connect as the given global user, and check that the
local server is not restricting access.

Relared Errors:
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
ORA-28042:
Server authentication failed
ORA-28043:
invalid bind credentials for DB-OID connection