What is znb in sap?

Often, creating a purchase order (PO) in SAP Materials Management (MM) with reference to another purchasing document is both necessary and quite effective and efficient. Dear all, I am trying to have MRP create purchase Req created by MRP to have custom document type ( ZUB, ZNB) and when this purchase req. SAP Purchase Order Znb Transaction Codes: ME21N — Create Purchase Order, ME22N — Change Purchase Order, MIGO — Goods Movement, NACE. SAP Znb Standard Po Transaction Codes: MIGO — Goods Movement, MIRO — Enter Incoming Invoice, SU01 — User Maintenance, ME21N — Create Purchase. SAP ERP was introduced so that procurement can be done efficiently in terms of time and cost. Dear SAP Experts, My Client is looking for different Document types for Purchase Order with different Serial.