Capacity Leveling in MPS and MRP 
The task of material requirements planning is to guarantee material availability. The system calculates which materials must be procured or produced at what time and in what amounts so as to provide the quantities required.
Using MPS you can carefully plan important parts or bottleneck parts in a separate planning run at the highest BOM level before the planning results have an effect on all of the production levels.
Lead time scheduling and the calculation of capacity requirements in MRP and MPS provide the basis for the creation of a master plan that corresponds to capacity planning. This way the MRP controller obtains information about possible bottlenecks and overloads. Before the master plan becomes effective and the planning results affect subordinate BOM levels, the MRP controller can make changes that affect capacity for chosen materials.
Scheduling
Before capacity planning can take place you must create capacity requirements within lead time scheduling, that is, determine the production dates. The system only generates capacity requirements if it executes lead time scheduling using the times specified in the routing.
Scheduling in MRP and MPS determines the basic dates and the production dates for the planned order. The basic dates define the earliest and latest dates for production. The production dates use the times in the routing to determine the start and finish of production as well as of the individual operations.
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