DNS query latency.

Hi Everyone,

We are having issues with DNS queries. I have two app servers running oracle in the back end. and they are using our public DNS. And our DNS server is Windows box. Customer calls saying application loads very slow. I go to the app server and run dig +trace command and it gets hung for about 30 sec up to 1 min.

1- Checking system resources and they are fine.
2- Checking DNS server box resources its fine too, no network errors or any indication of issue.
3- Checking Network connectivy from client to DNS. No issue.

Once I changed from our public dns to 8.8.8.8 to primary it fixed the issue but next day around same time application got slow. did same command dig +trace its hung again. Changed back to our public DNS its fixes the issue of cause only till next day. Again around same time it gets hung and after 30 -40 min issue resolved itself.

Run out of Ideas what might be wrong? and how to diagnose the issue. Windows guys telling me that DNS server is good no problem there. Network team has the same answer. So please advice what to do?

Thanks