You can reserve inventory quantities for sales orders when you create or edit sales order lines. If available inventory quantities are reserved automatically, then reserved inventory cannot be withdrawn from the warehouse for any other orders.
Inventory is reserved according to the setup of:
Manual or automatic reservation.
Reserved ordered items or only items on-hand.
The general setup and reservation rules that are valid when an order is created, are valid for the order until you make manual changes to the base data of the order. For example, if automatic reservation is selected when the order is created, any changes or additions to the order lines are reserved automatically until you change the value in the field on the order line on the ( tab).