You can delete the order in 7.1.1 (F5, CTRL-D, <DELETE> button depending on the UI). This will create "debooking" tr_hist records (ORD-SO) and delete the so_mstr / sod_det records. The standard system deletes sales order records when the order is shipped, invoiced & the invoice is posted if all lines are shipped. The so_mstr / sod_det records are copied to ih_hist / idh_hist records and then deleted.