ORA-28509: unable to establish a connection

admin

ORA-28509: unable to establish a connection to non-Oracle system
Cause: Initialization of adatabase link to a non-Oracle system failed to connect to
the Heterogeneous Services agent process for this non-Oracle system.
Action: Check the Net8service name definition in the following places: -- the
USING clause of the CREATE DATABASE LINK statement -- the
TNSNAMES.ORA file -- the Oracle Names Server The following are possible
reasons for name mismatches: -- The USING clause in the CREATE DATABASE
LINK statement has to match the service name defined in the TNSNAMES.ORA
file or in the Oracle Names Server. -- The protocol-specific information in the
service name definition must match the protocol-specific definition of the
responding listener. -- The SID=<name> in the service name definition (inthe
TNSNAMES.ORA file or in Oracle Names Server) must match the value in the
LISTENER.ORA file for the responding listener.