How to remove relationship or SO and PO?

How to remove relationship or SO and PO?

What are the steps to remove relationship between Sales Order and Purchase order?

Scenario: Customer places order and eligible for BO, Create the PO against the Sales Order.

There can be two scenarios why the sales order should de link  with PO 

  i) You get a rush order which can be fulfilled with the PO generated for another Sales order.
  ii) Customer Cancels or changes  the order before shipping.


Appreciate your help.