Material effectivity is usually used to represent the first time a part has been made available to a plant. It is not used to determine when a new part would be included into a product, and has no impact on MRP runs that generate production orders, etc. This is because effectivity has no real meaning in ERP unless it’s in the context of a next level assembly. BOM effectivity is used to control the actual incorporation date of parts into the built product. BOM effectivity is used in MRP runs, which in turn drive production orders, etc. that are required to build the product.