Optional reservations can be controlled via the category rack or by using the report option control. If you enter an option date (option until) in a reservation, the reservation status must always be O – optional, as a guaranteed reservation may not have an option date. Likewise, a reservation with the status O – optional must always have an option date.
Use registry-entry [511207] to define the market codes that are entitled to enter an indefinite number of optional reservations.