> But what happens if
> the computer suddenly shuts down after commiting some lines of the order but
> before ending the order.

You should place the open orders into an additional table not yust
decreasing the number ov available stock.

In this auxiliary table there should be an timestamp that allows you to
remove old items. An alternative (or addition) would be to use an
Connection-trigger to remove temporary items when client disconnects.

Once the order becomes final client does remove temporary items and
update stock within an short transaction.

Elmar