How To Fix /IWFND/MED_SVC_MU_LA028 - Reference type for ID '&1' not declared

SAP Error Message - Details

• Message type: E = Error

• Message class: /IWFND/MED_SVC_MU_LA -

• Message number: 028

• Message text: Reference type for ID '&1' not declared

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message /IWFND/MED_SVC_MU_LA028 - Reference type for ID '&1' not declared ?

  The SAP error message /IWFND/MED_SVC_MU_LA028 Reference type for ID '&1' not declared typically occurs in the context of SAP Gateway and OData services. This error indicates that the system is unable to find a reference type for the specified ID, which can happen for several reasons.
  Causes:
  
  Missing Reference Type Declaration: The reference type that is being called in the OData service is not declared in the metadata.
  Incorrect Service Registration: The OData service may not be properly registered or activated in the SAP Gateway.
  Model Issues: There may be issues with the data model or the way entities are defined in the service.
  Transport Issues: If the service was transported from one system to another, the reference types may not have been included in the transport.
  Versioning Issues: If there are multiple versions of the service, the reference type may exist in one version but not in another.
  
  Solutions:
  
  Check Metadata: Verify that the reference type is correctly defined in the service's metadata. You can do this by accessing the OData service's metadata URL (e.g., /sap/opu/odata/sap/YOUR_SERVICE_NAME/$metadata).
  Service Registration: Ensure that the OData service is properly registered and activated in the SAP Gateway. You can check this in the SAP Gateway Service Builder (transaction code /IWFND/MAINT_SERVICE).
  Rebuild the Service: If there are changes in the data model, you may need to regenerate the service. This can be done in the Service Builder by selecting the service and choosing the "Regenerate" option.
  Check Transport Requests: If the service was transported, ensure that all necessary objects, including reference types, were included in the transport request.
  Debugging: If the issue persists, consider debugging the OData service to trace where the error occurs. This can provide insights into what is missing or misconfigured.
  Consult Documentation: Review SAP documentation or community forums for any known issues related to the specific version of SAP you are using.
  
  Related Information:
  
  Transaction Codes:
  
  /IWFND/MAINT_SERVICE: To manage OData services.
  /IWFND/ERROR_LOG: To view error logs related to OData services.
  
  
  SAP Notes: Check for any relevant SAP Notes that might address this specific error or provide additional troubleshooting steps.
  Community Forums: SAP Community and other forums can be helpful for finding similar issues faced by other users and their solutions.
  
  By following these steps, you should be able to identify and resolve the issue related to the error message /IWFND/MED_SVC_MU_LA028.