ORA-28557: unknown string for database link to non-Oracle system
Cause: When attempting to connect 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 to check setup of the connection and the Heterogeneous Services agent
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