I have got a question about the behaviour of the SNP heuristic in relation to the creation of purchase requisitions (PR's).

1) I plan both in daily and monthly buckets in the heuristic planning book.  For the monthly buckets the SNP heuristic plans  1 PR per month. These PR's get a date that's in the middle of the month. This is not what I want. I want the PR to be placed at the beginning of the month (at the beginning of the time bucket). How can that be done?

2) There is a behaviour of the SNP heuristic that I do not like and that I would like to change. The issue is this: In a situation where there are a couple of already existing Purchase Orders (PO's), but in between these PO's there is still an uncovered demand, the heuristic plans a PR in between the PO's to cover the demand. That looks smart, but my customer does not like
that, reason: In the case that PR's are placed in between the PO's there is an additional commitment created and in fact the later PO's should be scheduled forward in favor of creating the new PR. Sometimes even a PR is created while the day after the PR-date a PO exists that covers all the demand already. The additional PR then leads to too many supply. This is a big issue because we also want to use the automatic conversion of PR's to PO's. right now manual changes are made to the heuristic output and that's an undesirable situation.

Question: Can the SNP heuristic be influenced so that it only creates PR's after the last PO (or something like that)? I don't want to go in the direction of the PP/DS heuristic by the way! Can the SNP heuristic be influenced by changing macro's in the heuristic plan book, I guess so, but what is the exact trigger for the heuristic, is it the "target stock"? If it is the "target stock", is changing the macro for "target stock" a wise way of influencing the heuristic behaviour or are there better ways?
 

For your first question;
Go into product master data of each product that you want to plan with SNP Heuristic. In product master data, go into Lot Size Tab. There there are two parameters, one called "Availability Date", the other  called "Period Factor".
If you set "Availability Date" empty then by default SNP Heuristic creates PRs in the middle of each bucket. If you set this parameter "X" then APO gives the power of changing the PR date to you. When this parameter is set as "X" then the other parameter "Period Factor" becomes useful. The PR date changes according to the number you write in "Period Factor". If you set this parameter "0.001" then SNP Heuristic creates PRs in the beginning of buckets. If you set this parameter as "1" then SNP Heuristic creates PRs at the end of buckets. You can arrange the date by trying numbers between 0.001 and 1. If you set this parameter as "0" then APO understands it as it is empty and acts as if it is 0.5.

For your second question;

There is a parameter again in Product Master Data, in Demand TAB called Maximum Latest Receipt.If you set this parameter as 100 hours then this means that you let the program to use receipts which are placed between (requirement time) and (requirement time + 100 hours). Then program may fulfill its demand or requirement with a receipt - a PO for example - that
is placed 50 hours later than the requirement eg. and it doesn't create any additional new receipts - PRs. So there would be no excess stock. But this is used in PP/DS or CTM (since it is related with dynamic pegging strategy), so I'm not so sure that it will be usefull for SNP Heuristic. But I suggest you to try and see.
 

As your first question has been answered yet, I will try to help on the second one. As far as I know, there is no parameter in SNP that will do exactly what you want. Work-around alternatives that I imagine are:

- Define a Stock Transfer Horizon in the product-location master data. No Purchase Requisitions will be created in this horizon. The problem is that it's a fix horizon and will not search if a PO exists or not.

- Change the Safety Stock macro calculation. Introducing the correct safety stock values you will be able to obtain what you want. To avoid SNP to plan when there is a shortage you will have a introduce a negative safety stock.
In this way you can avoid the heuristic to propose you any new PR. You will have to modify the safety stock until the macro detects that no more POs exists.
It's possible that modifying other key figures as Target Stock you can acheive the same result, but I haven't test it

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