How To Fix /IWFND/CM_MGW_RT157 - Type of data container returned by DPC is wrong. '&1' is expected

SAP Error Message - Details

• Message type: E = Error

• Message class: /IWFND/CM_MGW_RT -

• Message number: 157

• Message text: Type of data container returned by DPC is wrong. '&1' is expected

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message /IWFND/CM_MGW_RT157 - Type of data container returned by DPC is wrong. '&1' is expected ?

  The SAP error message /IWFND/CM_MGW_RT157 indicates that there is a mismatch in the type of data container returned by the Data Provider Class (DPC) in an OData service. Specifically, the error message states that the expected type of data container is not being returned, which can lead to issues in data processing and rendering.
  Cause:
  
  Incorrect Data Type: The DPC is returning a data type that does not match the expected type defined in the service metadata. This could happen if the DPC is incorrectly implemented or if there are changes in the data model that have not been reflected in the DPC.
  Model Changes: If there have been recent changes to the underlying data model (e.g., changes in the database tables or structures) that are not reflected in the OData service, this can lead to type mismatches.
  Service Definition Issues: The service definition (e.g., the service metadata) may not be correctly aligned with the implementation in the DPC.
  Serialization Issues: There may be issues with how the data is being serialized before being sent back to the client.
  
  Solution:
  
  Check DPC Implementation: Review the implementation of the DPC to ensure that it is returning the correct type of data container as expected by the OData service. Make sure that the data structure matches the expected output.
  Update Service Metadata: If there have been changes to the data model, ensure that the service metadata is updated accordingly. You may need to regenerate the service or update the data model in the service definition.
  Debugging: Use debugging tools to trace the execution of the DPC and identify where the incorrect data type is being returned. This can help pinpoint the exact location of the issue.
  Check Service Configuration: Ensure that the service is correctly configured in the SAP Gateway and that all necessary settings are in place.
  Test with Different Clients: Sometimes, the issue may be client-specific. Test the OData service with different clients (e.g., Postman, SAP Fiori) to see if the issue persists across different environments.
  
  Related Information:
  
  SAP Gateway: The SAP Gateway is responsible for exposing SAP data and processes as OData services. Understanding how the Gateway works can help in troubleshooting issues related to OData services.
  OData Service Metadata: Familiarize yourself with the OData service metadata, which defines the structure of the data being exposed. This can help in understanding what types are expected.
  SAP Notes: Check for any relevant SAP Notes that may address known issues or provide guidance on similar error messages.
  Documentation: Refer to the official SAP documentation for OData services and the SAP Gateway for best practices and troubleshooting steps.
  
  By following these steps, you should be able to identify and resolve the issue causing the /IWFND/CM_MGW_RT157 error message.