Can delivery priority be use to defined that certain material will be delivered before other with same data?
Example: sales order X for customer A with CRD 19.01 with material C, and sales order Y for customer B with CRD 19.01 with also material C. But no stock for both orders.
On a mass delivery delivery who will have the existing material?
What criteria did you use to search the site?
I used the following terms in onedx.find.sap.com (the search URL which you get after pressing the magnifier button in the top right of the page): "delivery priority"+atp.
In the first page of results there is a wiki, which explains with an example exactly the case which you described when you run rescheduling.
Use the terms that I mentioned and you will easily find the answer by yourself.