In this IMG activity you define for each checking group and initiator whether the material master record should be blocked for other orders during the availability check. If it is blocked, you cannot create two orders for the same material at the same time.
Using the Initiator field you can define the block separately for sales and shipping.
A block may, for example, be necessary if the material stock is low. In theory, if the material were not blocked during the availability check, two orders could be confirmed with the result that the quantity available is not sufficient for both orders.
You cannot yet change the values for the field "Initiator of the availability check" (sales order, delivery note) in the configuration menu.