Programs that query a name server are called resolvers. Because many TCP⁄IP applications need to query the name server, a set of routines is usually provided for application programmers to perform queries. On z/OS®, these routines are available in the resolver provided by z/OS Communications Server.

z/OS Communications Server provides programs for interactively querying a name server:
  • onslookup/nslookup (z/OS UNIX)
  • DIG (TSO)
  • dig (z/OS UNIX)
  • host
Note: The nsupdate program also makes queries to name servers as part of its operations.

For information on these programs, see z/OS Communications Server: IP System Administrator's Commands.

The onslookup command and the dig command use the resolver initialization facilities of the resolver provided by z/OS Communications Server, but use their own resolver for any additional resolver facilities needed.