Can anyone tell how 'Order Advice by Warehouse' checkbox works in Session Generate Order Advice - SIC (whina3200m000), I have done order method set up both at item ordering level as well as item warehouse level.

When i am trying to generate planned advises, system is referring item ordering level set up only, with this check box checked and unchecked.

If you have same item stored at 2 warehouses and you want to separately order them out (without clubbing the order), the you can use this functionality of "order advice by warehouse". If you have only one warehouse then it won't make any difference.