Primary Resource Assignment to Operations 
Use
You use this function to determine the resource or the part of the production line that is used to carry out an operation and the subordinate phases.
As phases are subdivisions of an operation, the system automatically copies the primary resource of the operation to its phases. The primary resource is committed for the entire duration of the operation and its phases.
Integration
The following resource data can influence the way operations and phases are processed:
Formulas that you can use to calculate the dates and costs of the phases in scheduling, capacity requirements planning, and costing
Default values that help you to edit certain operation and phase data
If labor capacity has been assigned to the primary resource, you can enter the number of employees required for the phase in the general phase data. The system uses this number for the following evaluations:
Prerequisites
The master record of the resource you want to use as the primary resource has been created in the system. The resource meets the following requirements:

Features
You can only assign one primary resource to an operation. When assigning resources, bear the following aspects in mind:
If operations are externally processed, you must only assign a resource to them if the control key assigned to the phases specifies that they are scheduled using their standard values.
If you can make a definite decision in the master recipe, you immediately assign the resource you want to use for production.
If several resources can be used, you can assign a
Before releasing the order, you replace the planning resource with a suitable production resource. You can use
system-aided resource selection for this, provided that you define the relevant criteria in the master recipe and resource.If an operation is purely used for production, you select a processing unit or labor resource as the primary resource.
If you also want to place the material into intermediate storage during an operation, you use a
Special Features for Resource Replacement
If you replace a resource that you have already assigned somewhere with a different resource, note the following:
However, standard values you have defined for the old resource are not deleted. For this reason, check all standard values after replacing a resource.
default values and activity types are only copied from the new resource when they have been marked as references in the resource.
Activities
You enter the primary resource for an operation on the operation overview (see
Editing Operations/Phases on the Operation Overview).