matearial ATP checks

HI experts,

I have a scenario as mentioned below--

there are two plants say one is 500 & another is 600.planning plant is 600.now in plant 500 there are 5 p/cs & in plant 600 another 5 p/cs available material & i need to create maintenance order for plant 500 , for which I need 10 p/cs of material.so whether system will check material availability for both plants & will create reservation for 10 p/cs? or it will check only for plant 500 & will create reservation only for 5 p/cs?please explain in details.thanks in advance.

rgds

rajib