How To Fix /IWBEP/CM_SBMC_MPC020 - Left End Cardinality is not specified for Association '&1'

SAP Error Message - Details

• Message type: E = Error

• Message class: /IWBEP/CM_SBMC_MPC -

• Message number: 020

• Message text: Left End Cardinality is not specified for Association '&1'

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message /IWBEP/CM_SBMC_MPC020 - Left End Cardinality is not specified for Association '&1' ?

  The SAP error message /IWBEP/CM_SBMC_MPC020 Left End Cardinality is not specified for Association '&1' typically occurs in the context of SAP Gateway and OData service development, particularly when defining associations in the Data Model (MPC) of an OData service.
  Cause:
  This error indicates that there is an association defined in your OData model where the left end (the source entity) does not have a specified cardinality. Cardinality defines the number of instances of one entity that can be associated with instances of another entity. In this case, the left end of the association is missing this specification.
  Solution:
  To resolve this error, you need to specify the cardinality for the left end of the association in your OData model. Here are the steps to do this:
  
  
  Open the Data Model (MPC) in your project: This is usually done in the ABAP Development Tools (ADT) or the SAP Web IDE.
  
  
  Locate the Association: Find the association that is causing the error. It will be referenced by the name &1 in the error message.
  
  
  Specify Cardinality: 
  
  For the left end of the association, you need to define the cardinality. Cardinality can be defined as:
  
  0..1 (zero or one)
  1 (exactly one)
  0..n (zero or many)
  1..n (one or many)
  
  
  Update the association definition to include the appropriate cardinality for the left end.
  
  
  
  Activate the Changes: After making the changes, make sure to activate the Data Model.
  
  
  Test the OData Service: Once activated, test the OData service to ensure that the error is resolved.
  
  
  Related Information:
  
  OData Model: Understanding how to define entities, associations, and cardinalities is crucial for OData service development.
  SAP Gateway: Familiarity with SAP Gateway and its components (like the Model Provider Class and Data Provider Class) is essential for troubleshooting and developing OData services.
  Documentation: Refer to the official SAP documentation for OData services and the specific version of SAP Gateway you are using for more detailed guidance on defining associations and cardinalities.
  
  By following these steps, you should be able to resolve the error and ensure that your OData service functions correctly.