How to remove uniqueness check on Person.PersonnellNumber?

Question

We have 2 HR systems with overlapping employee numbers. And currently import fails for some users because PersonnelNumber must be unique. 
 I know how to configure column values to be unique https://support.oneidentity.com/identity-manager/kb/267421/force-a-unique-value-for-column-in-identity-manager 
 but the system does not allow me to delete OOTB validation of PersonnelNumber. 
 I realize that I can introduce a custom field to store it, or I can concatenate employee number with ImportSource but I wonder if it is possible to just delete standard validation. 
 
 I found a similar question but it was not answered https://www.oneidentity.com/community/identity-manager/f/forum/20073/implement-multicolumn-uniqueness-for-default-table-i-e-qerresource 
 We are using 8.1.0

Markus Weiss-Ehlers · Answer

There is a workaround for your issue. You can assign an additional column to the default UniqueGroup for Person.PersonnelNumber. 
 To do that, use the Object Browser to create a new entry in the table QBMUniqueGroupHasColumn, referencing the UniqueGroup for Person.PersonnelNumber and a unique column, for example, the PK column Person.UID_Person.