You maintain the MRP data in the material master record of the material for which you would like to carry out production lot planning.
You create a number for the production lot. The system creates a WBS element during the creation. This is the number of the production lot. The planning, production and cost determination of the assembly are carried out using this number. If you would like to use the same work breakdown structure BOM for several production lots of an assembly, you have to designate the first production lot, which you create for the assembly, as the reference WBS element.
Normally, you have already created a material BOM. This is used as a reference when creating the work breakdown structure BOM, which you can create for the production lot.
Normally, you have created a routing or a rate routing for the material to be planned. You can use these as a reference when creating the routing for the production lot.