Local host tables

By default, resolver first attempts to use any configured domain name servers for resolution requests. If the resolution request cannot be satisfied, local host tables are used. Resolver behavior is controlled by TCPIP.DATA statements.

The TCPIP.DATA resolver statements define if and how domain name servers are to be used. The LOOKUP TCPIP.DATA statement can also be used to control how domain name servers and local host tables are used. For more information on TCPIP.DATA statements, refer to Communications Server: IP Configuration Reference (SC31-8776).

The resolver uses the Ipv4-unique search order for sitename information unconditionally for getnetbyname API calls. The Ipv4-unique search order for sitename information is the following. The search ends at the first file being found:

  1. The value of the environment variable X_SITE

    The value of the environment variable is the name of the HOSTS.SITEINFO information file created by the TSO MAKESITE command.

  2. The value of the environment variable X_ADDR

    The value of the environment variable is the name of the HOSTS.ADDRINFO information file created by the TSO MAKESITE command.

  3. /etc/hosts
  4. userid.HOSTS.SITEINFO

    userid is the user ID that is associated with the current security environment (address space or task/thread).

  5. jobname.HOSTS.SITEINFO

    jobname is the name specified on the JOB JCL statement for batch jobs or the procedure name for a started procedure.

  6. hlq.HOSTS.SITEINFO

    hlq represents the value of the DATASETPREFIX statement specified in the base resolver configuration file (if found); otherwise, hlq is TCPIP by default.