SAP is an Enterprise Resource Planning software package. It is designed to automate a lot of the finance functions from order to delivery (clients buying from them) and procure to pay (buying raw materials).
It should not affect the size or frequency of orders, as that is a supply chain issue. It may affect the information they request from you in terms of quotes, confirmations, delivery notices and invoices. However, it shouldn't be a big issue once the new system is bedded in