Grouping, Pegging and Distribution (GPD) when run MRP for PS

Question

Dear all,
As you know, MRP is a core of Planning Process. So when you run MRP for PS, SAP can't check stock in general stock and project stock at the same time. Now, my client have accept to run MRP base on project stock. But there are some problem when they give me requirement and actually situation in their company. One of them as below:
They have 3 WBS element (WBS 1, WBS 2, WBS 3) and they use the same material A. Their requirement is they want to run MRP to plan material for 3 WBS.
Solution 1: use MD51 and run MRP for Project definition and each of WBS element have respective project stock, the system will generate some of planned order for each oder reservation. After that, I will convert all of planned order to PR => PO => Good Receipt for each WBS element. When run MD04, I can see the stock for each project stock for respective WBS element.
Ok, I will talk about the limited of this solution. I suppose after complete technical for all of order reservation in WBS 1 and in project stock of WBS 1 have 3 material A not be use. But in WBS 2 is missing 3 material A. So when I run MRP again for WBS 2 by tcode MD51, the system will generate new planned order for this missing material A. This is not logic because I have enough material A for reservation in WBS 1. So I suggest my client that you should transfer material A from WBS 2 to WBS 1, they agree with me if they don't have many WBS element. But they have about 300 WBS element and they can't do transfer posting between many many WBS element. This solution 1 is not be accept.
Solution 2: I use GPD for this requirement. Firstly I will group WBS 1, WBS 2 and WBS 3 into WBS group. So use tcode MD04, I can see only WBS group and all of order reservation in each WBS 1, 2, 3 be showed on MD04 table. When I run MRP, the system will generate planned order for them. After that, I will conver all to PR => PO => Good receipt to WBS group. And in MD04 table, I can see project stock for WBS group. I begin transfer material from WBS group to each WBS 1, 2, 3. When all of order reservation in WBS 1 is technical complete, the material in WBS 1 have 3 material A not be use. And in WBS 2, I have a new order reservation and it be assigned 4 material A. At this time, project stock on WBS group is 0 but in WBS 1 is 3. But when I run MRP by tcode MD51, the system generate planned order with amount is 4. I wonder that why SAP does not check all material on all WBS element in WBS group to suggest a planned order with amount is 1. If SAP can solve this problem, my client will be accept this solution.
Hoping you support me.
Thanks, Regards
Hoai Vu

Answer 1

Hi Ahmed Rifaee
Thanks for your reply, I will talk about process in SAP.
So, I have 2 WBS element, that's simple because my project is have about 200 WBS element.
WBS1 have 2 order reservation for each actvity and material A0001 be use in 2 order reservation.
Order Reservation 1 needs 3  A0001
Order Reservation 2 needs 5  A0001
WBS2 have 1 order reservation for each activity and material A0001 be use in it
Order Reservation 3 needs 4  A0001
1.)     If I don't group 2 WBS1 and WBS2 to one WBS group, SAP will have 2 project stock for each WBS. and when I run MRP, WBS1 and WBS2 run independent base on current project stock at each WBS. So, although project stock WBS1 is run out of A0001 while A0001 still exist A0001 in project stock WBS2, SAP still generat planned order for missing part A0001 in project stock WBS1.
2.)     If I use GPD by group WBS1 and WBS2, I can solve this problem easy because they will use only one project stock for WBS group. Ok, after I good receipt A0001 into project stock, I'm sure that I have enough A0001 for 2 WBS1 and WBS2. But I can trace which reservation be ordered to delivery to them exactly. I try to use tcode MD09 to trace from Purchase order to Order reservation but I have just to trace in case PO have not been good receipted. I wonder that Pegging can help me in this case (PO have been good receipted).
Can you give me any idea for these problem
Thanks, Regards
Hoai Vu