Best practices to notify supplier's for Goods and Services/Items delivery in iProcurement OR Purchas

Hello,

I would like to know whether there is any functionality in Oracle that we can notify supplier's to delivery Items/Goods and Services.

Let me explain our current business scenario. Our current business user's first creates a Non-Catalog Requisition(iProcurement) for 100 units and then Purchasing staff creates a Standard PO and encumber the funds for 100 units.

But business may not require all the units at a time. Depending upon business requirement they contact supplier manually(by phone/email) and request for the delivery for required quantities.

So here is my question, instead of business user's contacting supplier manually every time, is there any functionality available in iProcurement OR Purchasing to notify suppliers to delivery the required quantities?