Hello
Please take a look on the following link from SAP Help where this strategy is described:
Net Requirements Planning (10) - Demand Management (PP-MP-DEM) - SAP Library
On this link you will find the information below about this strategy:
This planning strategy is particularly useful in mass production environments; it is often combined with repetitive manufacturing. You should choose this strategy if you want production to be determined by a production plan (Demand Management) and if you do not want sales orders to influence production directly. One of the most important features of this planning strategy is that it enables you to smooth the demand program.
It means that the purpose behind this strategy is that the sales orders will not affect the planning results.
I suggest you to take a look on the following link where the planning strategies are described and choose a different strategy for your material:
Strategies for Make-to-Stock Production - Demand Management (PP-MP-DEM) - SAP Library
The most common planning strategy is strategy 40, where the sales orders will generate planned orders.
You should also consider that a changing on the material strategy will not affect existing sales orders, only the newly created.
Best regards
Caetano Almeida