With the SAP Business ByDesign You can use various forecasting methods to create forecast requirements interactively in rolling time spans (for example, months) in the business scenario forecast requirements planning. You can then release the forecast requirements for procurement planning. You normally use forecast requirements planning to plan forecast requirements within medium or long-term planning horizons for the “make-to-stock” and “planned procurement” business scenarios.
Before you create a new periodic forecast for an existing demand plan, you must consider possible changes, such as planning horizons and new or discontinued products. If necessary, you can create a new demand plan.
In the Initiate Requirements Planning business process, all preparation steps are available to you that are required to carry out the requirements planning. This process is fundamental for correct and periodic demand planning.
You can use the Plan Demand business process to create and edit forecasts in a consistent hierarchy of different planning levels. Historical data on the products are collected in order to calculate forecasts based on selected forecast models. The process also supports the implementation of the interactive, periodic requirements planning and the transfer of the forecast requirements to the procurement planning.
Source: help.sap.com, as of March 2017