Hi Sudhakar,
go to http://help.sap.com/bni?current=srm, then Ariba Network Integration 1.0 for SAP Business Suite. Check out the Administrator's Guides for Buyer Integration and for Integration of SAP SNC (if the latter is applicable in your context). The buyer integration document talks about the following supported processes. Forecasting is part of the Collaborative Supply Chain processes. You should find the details in the documentation.
