Messages generated by the resolver for the autonomic quiescing of unresponsive name servers function

If the resolver detects that a name server is not being responsive, a series of network operator messages is issued that relate to that name server. For example, if a name server is operating at IP address 10.42.35.200 and the UNRESPONSIVETHRESHOLD value is 100, then the following sequence of messages might be generated by the resolver:

1. At the end of a 30-second monitoring interval, the resolver determines that the name server failed to respond to 100% of the 500 queries that were attempted by the resolver. The resolver considers the name server to be unresponsive and issues the following messages:

   EZZ9311E STOPPED USING NAME SERVER AT IP ADDRESS 10.42.35.200
   EZZ9313I NAME SERVER 10.42.35.200
        TOTAL NUMBER OF QUERIES SENT         500
        TOTAL NUMBER OF FAILURES             500
        TOTAL NUMBER OF RESOLVER POLLS SENT    0
        TOTAL NUMBER OF POLL FAILURES          0
        PERCENTAGE                           100%

   After issuing this message, the resolver sends only DNS polling queries to the unresponsive name server.
2. At the end of a subsequent monitoring interval, the resolver determines that the name server failed to respond to 10% of the 10 or more DNS polling queries during the last two monitoring intervals. This percentage is below the 100% threshold value, so the resolver considers this name server to be responsive again. The resolver clears message EZZ9311E from the operator console and issues the following message:

   EZZ9312I RESUMED USING NAME SERVER AT IP ADDRESS 10.42.35.200

3. After the resolver issues message EZZ9312I, it resumes sending DNS queries that are generated by an application to the name server.
4. The resolver also clears message EZZ9311E from the operator console if any of the following events occur:
   • The network operator disables the monitoring function using the MODIFY RESOLVER,REFRESH,SETUP command. For more information, see Steps for modifying the UNRESPONSIVETHRESHOLD value.
   • The network operator enables the network operator notification function using the MODIFY RESOLVER,REFRESH,SETUP command. For more information, see Steps for modifying the UNRESPONSIVETHRESHOLD value.
   • The autonomic quiescing of unresponsive name servers function abnormally terminates because of a system error.
   • The resolver is stopped.

The resolver issues individual messages for each name server that it considers to be unresponsive at the end of a given monitoring interval. Because the resolver calculates the responsiveness of a name server at every interval, messages might be issued for different name servers at different times, rather than notifications being issued about all unresponsive name servers at the same time. The resolver does not periodically reissue message EZZ9313I for each name server, but the status and current failure rate for each name server specified on an NSINTERADDR statement in the global TCPIP.DATA file is included in the MODIFY RESOLVER,DISPLAY command output when the autonomic quiescing function is active. The failure rate that is displayed is the percentage calculated by the resolver for the individual name server at the end of the last 30-second monitoring interval. For more information about the MODIFY command for the resolver address space, see z/OS Communications Server: IP System Administrator's Commands.