Define the reference key By default, reference fields store the sys_id of the record in the database. Before you beginRole required: personalize_dictionary About this task By defining a reference key, you can identify a field other than sys_id to use as the unique identifier for the reference field. The value of the reference key field, instead of the sys_id, is stored in the database for that reference field. Procedure Navigate to System Definition > Dictionary. Open the field record (for example, resolved_by on the Incident table). In the Reference key field, enter a field name on the referenced table (for example, email on the sys_user table). Note: Always choose a field from the referenced table that is both required and unique. Click Update.