Operations/Components Not Relevant to MRP 
Use
You can create production orders:
These order objects (operations, components) are not relevant to MRP, that is, they do not result in the creation of corresponding procurement elements (purchase requisitions planned orders).
You can specify that:
Prerequisites
This function is set up using the key Reservation/Purc.req in the order type-dependent parameters.
Features
When the order is created, the setting in the Res./Purc.req. key from the order type-dependent parameters is entered in the order header (key Res./Purc. req. tab page: Control). The order objects will then be processed according to these settings. The key also exists at component and operation level, and it describes the state of the object.
The key at order header level can be changed at a later stage. A change does not, however, have an effect on already existing order objects. In the case of newly added operations and components, the key in the order header is used.
When or how the activation of the order objects occurs depends on the characteristics of the Res./Purc.req. key. The key can have the following values:
This is a standard setting.

You have to consider the following dependencies when using this function:
Application
A possible application of this function could be as follows:
Activities
To maintain the Res./Purc.req. key in the order type-dependent parameters, choose Master data
® Order ® Define order type-dependent parameters in Customizing for Shop Floor Control.