After the transfer activity performed in a Incident/Request, the assignee_prev field on the Call Request table is not populated. Why?
All previous fields not only assignee_prev, for ex: group_prev, category_prev, status_prev are attributes that are declared as LOCAL attributes.
LOCAL attribute does not map to a DB field. They are created in memory to hold intermediate values or derived values internally by the Service Desk processes and are volatile.
We cannot guarantee the values of these variables over time. They should be considered as internal only fields. These variables should not be used to implement customization's.
Hence the value is not seen in the respective DB table.