If you choose the source allocation scheduling logic I, the system first tries to assign the purchase requisition B1 to the capacity period December and fails. In the second step, the system assigns B2 to the capacity period December. The system then assigns B3 to the capacity period November. Just like B1, B4 cannot be assigned because there are no more free capacities in December.

In the second program run, the purchase requisitions B1 and B4 should be rescheduled. The system attempts to assign B1 to the next period November and fails because the requirements quantity exceeds the free capacity quantity. B4 can, however, be assigned to the capacity period November:

In the third program run, B1 is assigned to the capacity period October. The cumulative capacity consumption is as follows:

If you work with the source allocation scheduling logic II, the system attempts to assign the first purchase requisition to the capacity period December. Since there are not enough capacities available in December, the system assigns B1 to the next capacity period November:

In the second step, the system assigns the second purchase requisition to the capacity period December:

In the third step, B3 should be assigned. The system attempts to assign the third purchase requisition to the capacity period November and fails because the available capacity has already been consumed by the allocation of B1. B3 is then scheduled backwards to the capacity period October:

In the final program run, the system attempts to assign B4 to the capacity period December and then to November. B4 is ultimately assigned to the capacity period October.