All name servers cache (store) the data they receive in response to a query. A caching-only server, however, is not authoritative for any domain. Responses derived from cached information are flagged in the response. When a caching-only server receives a query, it checks its cache for the requested information. If it does not have the information, it queries a local name server or a root name server, passes the information to the client, and caches the answer for future queries. The names and addresses of the root name servers are acquired from the servers listed in the hints file, the name and file path of which are specified in the name server's configuration file.
You can manually configure a name server to create a large cache of responses to queries that are frequently requested and reduce the number of queries made to master servers. The name server that you configure as a caching-only server stores data for a period of time determined by the time-to-live (ttl) value, and the cached information is lost if the name server is restarted.