Backward and Forward 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.

Creating Multiple Materials in Material Determination

Material Determination is used to swap one material for another.It is possible to get a list of materials for substituiton,but remember you can substitue only one material from the list.

This can be done through substituiton reason T Code [OVRQ]
See the substitution reason number for Manual Material Selection
- check the Entry box
- check the Warning box
- select A for Stategy
- save.

Go To VB11 to create Material Determination (taking into consideration that all the previous steps for material determiantion i.e. maintaining condition types,maintaining procedures for material determination and assigning procedures to sales doc. types have been done)

Create one material determination,dont forget to give the Subst reason on top and also on the line.

Click the Variants Icon on top left-Sreen opens

Specify different materials you want to swap with the material you have enterd

Note that the subst reason is already copied on the screen

Remember materials should be of the same sales area,atleast Divisions should be same

SD material Determination based on availability check

For SD material Determination you can create a Substitution reason and on the Strategy field, the following info. is available:

Product selection in the background is performed on the basis of the availability check.

We want to have the material determination only in case on material shortage. We expect the Substitution reason to give us this functionallity. It does not hovever take the availabilty into account before substitution.

We thought the worse case is to create a ABAP which is linked to the "requirement" field in the Procedure (OV13).

Has anyone had the same requirement? Is this a bug or just incorrectly documented?

I also encountered this abnormally recently using material determination. In order to combat the problem, the first product substitution should be for the original material. I've illustrated this below:

Original Product: ABC
Substitutes: DEF, XYZ

In order to perform product substitution ONLY in the case of ATP failure for product ABC, structure the Material Determination record as follows:

Material Entered: ABC Substitutes: ABC
DEF
XYZ

There seems to be a devaition at availability check and or on a conceptual note still.

Availability check can be configured both at requiremnt class and at the schedule line categories level.

Whilst the availabilty check at the requirement class level via global and mandatory configuration the schedule line catgry availability check deals with the order.

It is mandatory that the reqmnt class is flagged off for avlblty check and the schdelu line cat need not be.

The following are the mandatory for Availability check to happen--

1. Must be swithced on at the requirment class level and at the schedule line level.

2. Reqmnt type must exist by which a requiremnt class can be found

3. There must exist a plant and is defined

4.Checking group must be defined in Material Master records(it controls whthr the system is to create individual or collective reqmnt)

A combination of checking gropup and checking rule will determine the scope of availbaility check.

Availability Check on Quotation

SAP standard does not do an availability check on the quotation, as it is not a definite order, usually just a pricing quote.

When it is converted to an order, the first availability check is carried out, as well as credit checks. The system will check stock in the plant, plus what is contained in the availability checking rule (scope of check) eg: can add POs for replenishment, purchase reqs, different planned orders, and subtract sales orders, deliveries etc already created against that material in that plant (and possibly Storage location).

If there is enough stock in the plant/SLoc, the system will give you a confirmed date, or give you a date based on the production time or purchasing time from the material master. The date the system proposes is based on the customer's requested delivery date.

SAP first backward schedules looking at the required delivery date, less transportation time, less transportation lead time, less pick and pack time, less production/purchase time if applicable. If the date it calculates is equal or later than today’s date, then it will confirm the customer’s required date. If it falls in the past, SAP will then forward schedule for today’s date, plus the times listed above to get the date when the customer can actually have it.

ATP is the single most complex part of the SD module, depending upon how PP and MRP is set up.

MRP works semi-separately, depending on how it is set up. Basically, MRP looks at the demand on the plant, and if it the stock does not meet expected sales orders and deliveries, it will create a purchase requisition (outside purchase) or requirement or planned order (for production) to cover the shortfall. When MRP is started, it will turn the PR into a PO or the requirement into a production order.