Hi Raja Sekaran,
Scheduling Margin Key is used to populate the scheduled start date, scheduled finish date, release dates in production order. A customized SMK can be configured & needs to be maintained in the MRP view of material master.
Production scheduling profile is used if we want to auto release production order when its gets created or any documents attachment etc. If we want to do auto goods receipt also then, it can be maintained in the production scheduling profile. This profile needs to be assigned in the work scheduling view of material master.
NETCH: It is the planning processing key where only the materials in the planning file which have NETCH indicator are planned. This indicator is set automatically when we do some changes in the material like changing MRP type. Lot size etc.
NETPL: When we use this processing key, only those materials of planning file are picked which are having NETPL indicator. The materials wihich have undergone change in the planning horizon, will get this indicator. The planning horizon needs to be defined in the customizing.
NEUPL: All the materials which are in the planning file will be picked irrespective of indicator by system when we use this processing key. This key is generally used at the beginning of project to make sure that all the materials with MRP settings are taken up for MRP run.
Generally, MRP will be scheduled as a background job. Every night a background job with NETCH will run & every once in week a background job with NEUPL will run.
Also refer to the links given by experts.
Revert back for any clarifications.
Regards
Kalyan