The MIDM provides the ability to link the value of a specific source record field to the same field in the SBR. When you link an SBR and source record field, the value of the SBR field is always the same value as the field in that source record. If the field value is subsequently updated in the source record, the changes are shown in the SBR. The field values remain the same until the link is removed, at which point the survivor calculator immediately recalculates the best value for the field based on the source records in the profile. You can only link SBR and source record fields in the parent object and only if you have explicit security permissions to do so.