Why does Mig Object classification - Material (MARA) fail with "Assignment exists and is valid" ?

[SAPSupport]

In migration object “Object classification - Material (MARA)”, I completed upload file, prepare and mapping tasks.

However, in simulation, the error message  "Assignment exists and is valid" appears , why ?

------------------------------------------------------------------------------------------------------------------------------------------------
Learn more about the SAP Support user and program here.

[SAPSupport · Accepted solution]

Please refer to the KBA  Error ''Assignment exists and is valid' when using the Migration Object 'Object Classification 'to explain

The Migration Tool failed because there is already Classification for the object ( for example material  ) and class is already assigned.

This tool can work only on Objects without any Classification, by design.

If updating Material Master Classification , please check also the Blog How to mass update Material Classification in SAP S/4HANA Cloud