An issue is reported by customer, that SNP heuristic does not plan any receipt to cover the demands (supply shortage).
It is confirmed that customer has every master data set correctly, and source of supply is correctly determined.
And there is no error issued during heuristic planning.
Upon checking the issue by debugging, it is found that, the reason is that key figure funtion '3004' (Stock on Hand) is assigned to two key figures.
One is the auxiliary key figure 'STOCK', which could be seen in transaction /sapapo/sdp8b. This is a standard delivered setting by SAP in standard SNP planning book.
The other one is a customizing key figure in the planning area, which is set in transaction /sapapo/msdp_admin.
During SNP planning, key figures are read according to their key figure functions. So system will try to find a key figure with function '3004' to read stock on hand.
However in this customer's case, two key figures are found -- we cannot be sure which one to read -- it could be that auxiliary key figure 'STOCK' is correctly read by chance, by unfortunately here it reads the customizing key figure, which contains no value at all. This makes system does not find any supply shortage, of course no supply is planned.
This case is not common. In /SAPAPO/SDP8B, if you want to assign an auxiliary with a key figure function which is already in use by other key figure, you'll get an error message, and the same happens in /SAPAPO/MSDP_ADMIN. The only chance is that, you have assinged a key figure function to an auxiliary key figure in /SAPAPO/SDP8B when the key figure function is not in use by any other key figure; then you can still assign this key figure function to a key figure in /SAPAPO/MSDP_ADMIN -- the system cannot check the assignment situation of the auxiliary key figures in this case.
Basically, SNP does not support two key figures with same key figure function in a planning area, so you must take care when you set key figure function.
The further you go into SNP, the more you'll feel "key figure function" is important.