This feature is available on Artica 4.30 Service Pack 951 or Artica v4.40
In the left menu, Click on “DNS Firewall” .
On “Status” section, if your pool stores records in a cache, you can see a link on the title.
A new section appears listing all the records saved in the memory cache. You can search for them and click on the red trash in order to delete the item from the cache