Availability Check : Confirm Quantity becomes zero when insufficient stock

Hi Team,

I am facing an issue where Confirmed quantity becomes ZERO in sales order when there is insufficient stock.

Here is what I have done:

Material Code : FGABC01

Qty : 11496 Carton

Created order with quantity 11500 carton SAVED.

1. Executed transaction VKM3.
2. Upon displaying the order, the confirm quantity of the material is ZERO.
3. If I reduce quantity to 11496 or less then system confirms Order and Partial deliveries also allows.

There is No Credit or any other Block.

Checked part.dlv./item status which shows BLANK (Partial Delivery allowed).

Please help me to understand reason of this standard system behavior and suggest how to stop this.

Regards,

MJ.