Procurement via Materials Requirements Planning
Use
If you allocate a material with the
item category L and the corresponding settings in the material master to a network activity, the system generates a reservation for the material. A reservation is an internal document that defines the requirements of a material and reserves a specified quantity for the network activity.The material is procured using material requirements planning (MRP). For more information on requirements planning, see the
Requirements Planning (PP-MRP) component.As soon as the reservation is activated, the systems carries out an
availability check for the material in the next MRP run. If there is not enough material in stock to meet the requirements, the system creates a
planned order. Planned orders can be converted into production orders for the actual manufacture of the material component required or into purchase requisitions/orders. 
If a purchase requisition is generated the same process takes place as described in the graphic in
Direct Procurement.
If you use MRP, you still can decide whether to manufacture a required material internally or to buy it from an external vendor. However the decision will then be taken an MRP controller, who depending on your orgnization structure and the kind of material involved, may not be directly involved with your project.
