Message type: E = Error
Message class:  FKKINV - Invoicing in Contract Accounts Receivable and Payable 
Message number: 151
Message text: Reconciliation key &1 was deleted since it is not used
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The SAP error message FKKINV151 indicates that a reconciliation key has been deleted because it is not being used in the system. This message typically arises in the context of the SAP Contract Accounts Receivable and Payable (FI-CA) module, which is used for managing customer accounts and billing processes.
Cause: The error occurs when: A reconciliation key that was previously defined in the system is no longer associated with any active transactions or accounts. The system performs a cleanup process to remove unused reconciliation keys to maintain data integrity and optimize performance.
Solution: To resolve this issue, consider the following steps: Check Usage of Reconciliation Key: Verify if the reconciliation key is indeed not being used in any active transactions. You can do this by checking the relevant tables or using transaction codes like FKKINV or FBL5N to see if there are any open items associated with the reconciliation key. Recreate the Reconciliation Key: If the reconciliation key is needed
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