Hello Mani
Following are details are from old SAP Handbook, good information to understand the concept.
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- Net Change Planning
Automatic material requirements planning is especially hard on system performance for production processes with complicated BOM structures. To guarantee frequent planning runs of those materials which are relevant for planning despite this problem, you can carry out the planning run with the "net change planning" procedure. This process only plans those materials which have undergone a change relevant to material requirements planning (for example, change in a production order due to excessive scrap, a new sales order, and so on) since the last planning run.
The so-called planning file exists especially for the planning run and contains all the materials and their respective MRP types. If a material is changed in a way that is relevant to the planning run, it is given a net change indicator meaning that it will be included in the next net change planning run. In a net change planning run, only these materials are planned.
- Net Change Planning in the Planning Horizon
Performance can be improved even further by using the net change planning run in the planning horizon. Here, only those changes relevant to requirements planning that fall within a specific period (defined by the user and known as the planning horizon) are included in the planning run. It is advisable in this situation to carry out a total planning run in regular intervals (for example, weekly or monthly) to keep the planning results completely up-to-date.
- Regenerative Planning
It is also possible to carry out a regenerative planning run. In this planning run, the system plans all materials that are relevant for planning. Usually, the regenerative planning run is only carried out in the implementation stages.
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Hope this will help.
Thank you
Satish Waghmare