In a CMIP message, the information which determines the source of the message comes from three places. The CMIP string may specify the distinguished name of the instance sending the request or response. Or, the string may include the "&DN". macro. This is replaced by CMIP services with the distinguished name of the instance sending the message as identified by the local identifier supplied on the API call. Finally, a subtree manager instance is allowed to use the "&DN" macro and specify a source-override. This results in the distinguished name supplied on the override being substituted for the &DN rather than the DN of the subtree manager. This error indicates that the client application program specified a non-null value for the source parameter on a request or response (MIBSendResponse, MIBSendCmipRequest, MIBCmipRequest, MIBSendCmipResponse, or MIBCmipResponse) but the managed object instance sending the request or response is not a subtree manager.