Availibilty check during sales order creation and its relation to PP

Question

Hi all,
A critical scenario I am stuck in. My client has 3 plants viz. 1000, 1100, 1200. Plant 1000 gets sales orders from different customers and production happens on plants 1100 and 1200 through special procurement key. Customer A and customer B are very important for plant 1000. For customer A client allocates 25 tonnes per week and for customer B, 15tonnes/ week. The amount agreed can be changed at any time with the customer.  The purpose of this allocation is to reserve capacity for these customers in order to provide short lead time.
Capacity of plant 1100 is 200 tonnes per week( I am not sure where to define). If for last 3 weeks, capacity booked in plant 1100 is 190 tonnes including 15 tonnes of Customer A and 15 tonnes of Customer B , then plant 1100 can take orders for 10 tonnes more.When a person creates a sales order in plant 1000, it should show that plant 1100 has capacity available only for customer A and for other customers it should show later date for delivery.client wants to set a forecast demand of 25 tons/week for customer A and 15 tons/week for Customer B. As client receive specific orders from customer A or B, this should reduce the forecast tonnage accordingly.
How to map this?? kindly guide.
Regards.

Answer 1

ME,
The question is a bit vague, so I will give a correspondingly vague answer.
First, let me say that there is no ATP in ERP that directly confirms sales orders based on capacity availability.  However, you may not need this.
production happens on plants 1100 and 1200 through special procurement key
SPK only points to one plant.  So, for a given material or a given BOM, the source is one plant.  MRP will always plan for one source, regardless of preexisting capacity consumption.
The purpose of this allocation is to reserve capacity for these customers in order to provide short lead time.
You have left off the more important concept:  What happens to the remaining capacity?  This is what you need to limit. 
So, lets look at the parts where the SPK points to 1100 as a source.  You need to ensure that A gets 25 MAX, B gets 15 MAX, and 'everyone else' gets 160 MAX (200 - 25 - 15).  This can be achieved using product allocation.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/93/744d05546011d1a7020000e829fd11/frameset.htm
In the case where 'Everyone else' gets an unfavorable lead time (or an unconfirmable order) you can manually shift the production for those orders to plant 1200, provided capacity is available.
client wants to set a forecast demand of 25 tons/week for customer A and 15 tons/week for Customer B. As client receive specific orders from customer A or B, this should reduce the forecast tonnage accordingly.
Forecasting is OK, but a separate topic.  He can forecast and build any way he wants, and the forecast will be consumed according to whatever strategy he has selected.  However, it won't be relevant to ATP.  The only ATPs that use forecasting are against Planned independent requirements, which are not customer specific.
Best Regards,
DB49