ORA-28557: unknown string for database link to non-Oracle system Cause: When attempting toconnect to a non-Oracle system through a
Heterogeneous Services database link, the agent supporting this non-Oracle
system failed to return FDS_CLASS_NAME and/or FDS_INST_NAME. ORACLE
requires these names to configure the heterogeneous database link. Action: Contact the DBA tocheck setup of the connection and the Heterogeneous
Services agent.