MTL_DEMAND table not getting populated on order booking

MTL_DEMAND table is not getting populated when order is booked or sales order line is added to already booked order. However if I reserve the sales order line, MTL_DEMAND does get populated. I have made the profile option "OM: AUTOSCHEDULE" as Y .

I need to know the process via which records gets populated in the MTL_DEMAND and under what conditions.

I need this information in order to write a custom report which will show all the demands related to item for a given sub inventory. ( In our business process, user will always enter the sub inventory value while entering sales order lines)