Process Flow Of Layer Costing(FIFO) & Update?

Hello,

Please, I need the process flow of Oracle Layer Costing(FIFO) as it relates to Oracle Purchasing,Inventory and Cost Management in R12.How is the transaction originated from PO>INV>Cost Management?How is Layer number generated?How to update layer cost in Oracle Cost Management?

The issue we are currently experiencing is a user raises purchase order in Oracle Purchasing for the purchase of an inventory item(A4 Paper) for  two hundred(200) cartons and a unit cost of $50.However,one hundred(100) cartons were received initially into store or Inventory and payment was made.At another time the company also received the remaining one hundred(100) cartons of the A4 paper  with other charges like freight,handling charges,insurance etc.The user want to capture & update the Layer Cost of the A4 paper considering the fact that the company has incurred additional charges as earlier mentioned.What is the process flow in Oracle