Batch determination and availability check

Hello,

How is the batch determination in sales order/delivery related to availability check in sales order/delivery.

1 ) when the batch is determined in sales order, does the system does the ATP by considering the actual stock for that particular batch determined in sales order ?

2 ) what happens at the delivery level. ?

I think during PGI, the system checks for the actual stock for the batch which is determined in delivery ?

request pls answer pointwise.

regards

pamela