How To Fix /IWFND/CM_GSR021 - Duplicate ID or multiple nodes for an x..1 relation

SAP Error Message - Details

• Message type: E = Error

• Message class: /IWFND/CM_GSR -

• Message number: 021

• Message text: Duplicate ID or multiple nodes for an x..1 relation

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message /IWFND/CM_GSR021 - Duplicate ID or multiple nodes for an x..1 relation ?

  The SAP error message /IWFND/CM_GSR021 Duplicate ID or multiple nodes for an x..1 relation typically occurs in the context of SAP Gateway and OData services. This error indicates that there is an issue with the data being returned from the backend system, specifically related to the cardinality of the relationship between entities in the OData model.
  Cause:
  
  
  Duplicate IDs: The error suggests that the OData service is trying to return multiple records for a relationship that is expected to have a one-to-one (1..1) or one-to-zero-or-one (0..1) relationship. This can happen if the underlying data model in the database has duplicate entries for a key that should be unique.
  
  
  Incorrect Data Model: The data model defined in the OData service may not accurately reflect the underlying database structure, leading to mismatches in expected relationships.
  
  
  Improperly Defined Associations: If the associations between entities in the OData service are not correctly defined, it can lead to situations where the service attempts to return multiple records for a relationship that should only have one.
  
  
  Solution:
  
  
  Check Data Integrity: Verify the underlying database tables to ensure that there are no duplicate entries for the keys that are supposed to be unique. You can run SQL queries to identify duplicates.
  
  
  Review OData Model: Check the OData service definition in the SAP Gateway. Ensure that the associations and cardinalities are correctly defined according to the underlying data model.
  
  
  Adjust Service Implementation: If the service implementation is returning multiple records for a relationship that should be one-to-one, modify the logic in the service to ensure it only returns a single record.
  
  
  Debugging: Use transaction code /IWFND/ERROR_LOG to check for additional details about the error. This can provide insights into which specific request is causing the issue.
  
  
  Testing: After making changes, test the OData service to ensure that the error is resolved and that the data returned is as expected.
  
  
  Related Information:
  
  OData Services: Understanding how OData services work in SAP Gateway is crucial. Familiarize yourself with the concepts of entities, associations, and cardinalities.
  SAP Gateway Error Handling: Learn about the error handling mechanisms in SAP Gateway to better diagnose and resolve issues.
  Transaction Codes: Familiarize yourself with relevant transaction codes such as /IWFND/MAINT_SERVICE for managing OData services and /IWFND/ERROR_LOG for checking error logs.
  
  By following these steps, you should be able to identify the root cause of the error and implement a solution to resolve it.