How To Fix /IWBEP/SBUIOD059 - Cardinality N:N is not allowed.

SAP Error Message - Details

• Message type: E = Error

• Message class: /IWBEP/SBUIOD -

• Message number: 059

• Message text: Cardinality N:N is not allowed.

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message /IWBEP/SBUIOD059 - Cardinality N:N is not allowed. ?

  The SAP error message /IWBEP/SBUIOD059 Cardinality N:N is not allowed typically occurs in the context of SAP Gateway and OData services when there is an attempt to define a relationship between two entities with a many-to-many (N:N) cardinality. In OData services, relationships are generally expected to be one-to-one (1:1) or one-to-many (1:N), as many-to-many relationships can complicate the data model and the way data is represented in OData.
  Cause:
  
  Entity Relationship Definition: The error arises when the data model defined in the SAP Gateway service includes a relationship between two entities that is defined as many-to-many (N:N). This is not supported in OData services.
  Service Implementation: The service implementation may be trying to expose a many-to-many relationship directly, which is not allowed in the OData protocol.
  
  Solution:
  To resolve this error, you need to adjust the data model to eliminate the many-to-many relationship. Here are some common approaches:
  
  
  Introduce a Join Entity: Create a new entity that acts as a join table between the two entities. This join entity will have foreign keys referencing the primary keys of the two entities, effectively transforming the many-to-many relationship into two one-to-many relationships.
  
  For example, if you have entities A and B with a many-to-many relationship, create a new entity A_B that contains references to both A and B.
  
  
  
  Redefine Relationships: If possible, redefine the relationships to be one-to-many. This may involve changing the business logic or how data is structured.
  
  
  Update the Data Model: After making changes to the data model, ensure that you regenerate the OData service and update the metadata accordingly.
  
  
  Check Service Implementation: Review the service implementation to ensure that it aligns with the new data model and that it does not attempt to expose many-to-many relationships.
  
  
  Related Information:
  
  OData Protocol: Familiarize yourself with the OData protocol specifications, particularly regarding entity relationships and cardinality.
  SAP Gateway: Review the SAP Gateway documentation for best practices on defining entity relationships and service implementation.
  Testing: After making changes, thoroughly test the OData service to ensure that it behaves as expected and that the error is resolved.
  
  By following these steps, you should be able to resolve the /IWBEP/SBUIOD059 Cardinality N:N is not allowed error and successfully implement your OData service.