What do you mean by forward scheduling and backward scheduling?

Backward scheduling is the calculation of deadline dates: the arrival time at the customer site is calculated as the earliest possible goods receipt time at the customers unloading point on the requested delivery date. All four of the delivery and transportation scheduling lead times are subtracted from the customer’s requested delivery date to determine if this date can be met.
The transit time, loading time, and pick/pack time are subtracted from the customer’s requested delivery date to calculate the required material availability date.
The system calculates backward scheduling as follows:
Requested delivery date minus transit time = Goods issue date Goods issue date minus loading time = Loading date Loading date minus transportation lead time = Transportation scheduling date Loading date minus pick/pack time = Material availability date
By default, the system will calculate delivery dates the closest day, taking into consideration the working days of the shipping point and a rounding profile. In this case the system assumes a 24 hour work day and lead times can be entered in days up to 2 decimal points. This is referred to as daily scheduling.
Precise scheduling calculated down to the day, hour and minute is supported. This allows the scheduling of a delivery within a single day. It is activated by maintaining the working hours for a particular shipping point.
Backward scheduling is always carried out first. If the material availability date or transportation scheduling date is calculated to be in the past, the system must then use forward scheduling.
Forward scheduling is also done if no product is available on the material availability date calculated by backward scheduling. The system does an availability check to determine the first possible date when product will be available. This new material availability date forms the starting point for scheduling the remaining activities. The loading time, pick/pack time, transit time, and transportation lead time are added to the new material availability date to calculate the confirmed delivery date. *-- Soumyajit
Backorder Processing
Backorder processing is a functionality in SAP where you can change the committments and over-ride the blockage of stocks marked against sales documents/deliveries. For e.g. you receive an order from a very important customer for material "A" but the entire quantity of A is committed to another customer "B" via earlier sales orders and this is where BACKORDER processing helps you to change the committment and shift stock due for B to A. This is the benefit of this funtionality.
OMIH - Checking rule for updating backorders OPJL - Define new checking rule OPJJ - Define scope of check
V_RA - Backorder Processing
Data selection:- Sold-to-party Customer code Mandatory Sales Organization Mandatory Distribution Channel Mandatory Division Mandatory
Changed confirmed quantity :- Tick the material you want to changed and click the Backorder button Confirmed quantity that still can be changed are highlighted.
V.15 - Backorder List Sales Organization Mandatory Distribution Channel Mandatory Division Mandatory
Block Material in Sales Order