Error 0x8007213C

Value: -2147016388 | 0x8007213C | 2147950908

What does it mean ?

ERROR_DS_NONSAFE_SCHEMA_CHANGE  
Adding a new mandatory attribute to an existing class, deleting a mandatory attribute from an existing class, or adding an optional attribute to the special class Top that is not a backlink attribute (directly or through inheritance, for example, by adding or deleting an auxiliary class) is not allowed.
Value: 8508 | 0x213C | 0b0010000100111100

Where does it come from ?

FACILITY_WIN32  
Provides a way to handle error codes from functions in the Win32 API as an HRESULT. (Error codes in 16 - bit OLE that duplicated Win32 error codes have also been changed to FACILITY_WIN32)
Value: 7 | 0x007 | 0b00000111

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