Glynn C Williams on availability check

The Glynn C Williams Book says this on 'Controlling the Availability Check' [Page 191]:-

Both sales and delivery requirements are taken into account in the availability check in sales documents. However, in deliveries, only the delivery requirements are taken into account and there is a <b>danger that quantities reserved in the sales documents are considered to be available by the availability check in the deliveries This results in the deliveries being created and the material availability dates of the materials in the sales order being pushed out.</b>

what is the way to avoid this ?