Query About Payment Terms

Hi All

I am looking for a way by which the default Payment Terms can be changed.

In the Service Admin Guide, I found that the Application.Procure.DefaultPaymentTerms parameter specifies the default payment terms, which are used when there are no payment terms specified on an invoice, purchase order, contract, supplier, or other location.

Can somebody advice ? Who can change the default Payment Terms ? Can the Supplier or Buyer do that ? How they can do it ? Or do we have to raise a SR for Ariba everytime the default Payment Terms need to be changed ?

Thanks