Message type: E = Error
Message class:  CNV_DMC_SIN - Messages for s-innovations migration 
Message number: 401
Message text: Reference number Supplier &1 and Contract Partner &2 are filled
You want to create a customer for an already existing supplier or
contract partner with the same number. It is not possible to fill the
reference number for both supplier and contract partner.
The record will be skipped until the source file will be changed.
Please change your source file. Delete the reference number for customer
or contract partner. It is only allowed to fill one of the reference
numbers.
The system issues an error message and will not allow you to continue with this transaction until the error is resolved.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message CNV_DMC_SIN401 typically occurs during data migration processes, particularly when using the SAP Data Migration Cockpit (DMC) or similar tools. This error indicates that there is an issue with the reference number for a supplier and contract partner being filled inappropriately or conflicting with existing data.
Cause: Duplicate Entries: The error may arise if there are duplicate entries for the supplier and contract partner in the system. Incorrect Mapping: The mapping of the supplier and contract partner in the migration data may not align with the existing records in the target system. Data Integrity Issues: There may be issues with the integrity of the data being migrated, such as missing or incorrect references.
Configuration Issues: The configuration settings in the DMC or the target system may not allow for the combination of the specified supplier and contract partner.
Solution: Check for Duplicates: Verify if there are existing records for the specified supplier and contract
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV_DMC_SIN400 Conversion of Cycle value failed (format: &2; value: &3)
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_DMC_SIN399 Production version &1 already exists. Material is &2, Plant is &3
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_DMC_SIN402 Customer &1 is confirmed and differs from supplier &2 (see long text)
What causes this issue?  You want to create a customer for an already existing supplier with the same number. The mapping of supplier and customer are...
CNV_DMC_SIN403 Customer &1 is confirmed and differs from contract partner &2 (long text)
What causes this issue?  You want to create a customer for an already existing contract partner with the same number. The mapping of customer and cont...
Click on this link to search all SAP messages.