EZZ9311E

Explanation
 This message is issued when the resolver stops
forwarding  domain name server (DNS) queries that were generated by
an application to the specified unresponsive name server. A name server
is considered to be unresponsive when it fails to respond to resolver
queries at a  rate that exceeds the unresponsive threshold percentage
of the installation. Specify  the threshold percentage by using the
UNRESPONSIVETHRESHOLD resolver setup statement. The failure rate is
compared to the unresponsive threshold percentage at 30-second intervals.
 ipaddress is
the IPv4 or IPv6 network address of the name server that is considered
unresponsive.

System action
 Processing continues. The resolver continues
to send DNS queries that were generated by an application to responsive
name servers that are specified in the global TCPIP.DATA data set.
The resolver polls the unresponsive name server periodically to determine
when the name server is again responsive to DNS queries. The message
remains on the operator console until one of the following events
occurs:  During a future monitor checkpoint, the percentage of resolver
polling queries to which the name server has failed to respond drops
below the UNRESPONSIVETHRESHOLD percentage.
Operator intervention disables the resolver's autonomic quiescing
of unresponsive name server function.
The resolver is stopped.

Operator response
 Contact the system programmer.

System programmer response
 Determine whether the name server
is unresponsive as a result of a network condition, a configuration
error, or a temporary condition that might resolve itself later. If a network condition prevents resolver requests or name server
responses from reaching the correct destination, correct the network
condition. When the resolver polling queries are successfully responded
to, the resolver will clear the message from the operator console.
If a configuration error causes the name server to be unresponsive,
use resolver diagnostic tools such as MODIFY RESOLVER,DISPLAY or Trace
Resolver output to determine which of the following conditions causes
the error: If the UNRESPONSIVETHRESHOLD value specifies a lower percentage
of errors than what your network can tolerate during typical operations,
increase the threshold percentage in the resolver setup file. For
example, if the threshold percentage is 25%, but your network can
tolerate 40%, increase the threshold to a value in the range of 40%
- 45%.
If the IP address is no longer valid as a name server, remove
the IP address from the list of name servers to be used by the resolver.
The list of name servers is defined using the NSINTERADDR or NAMESERVER
configuration statements in the global TCPIP.DATA file.
If the RESOLVERTIMEOUT value is too low for responses to consistently
return from the name server within the specified time value, increase
the timeout setting to a value that permits a larger percentage of
responses to arrive within the timeout interval.
After you have corrected the configuration error, take one
of the following actions to cause the resolver to use the updated
configuration information: If you modified the setting of the UNRESPONSIVETHRESHOLD parameter,
instruct the operator to issue the MODIFY RESOLVER,REFRESH,SETUP=setup_file_name command.
If you modified the RESOLVERTIMEOUT parameter, or if you removed
an IP address from the list of name servers, instruct the operator
to issue the MODIFY  RESOLVER,REFRESH command.

If you eliminate a network condition and a configuration error
as the reason for the message, the resolver might be generating the
message for a temporary condition that might resolve itself. For example,
the name server might be having maintenance applied, or the name server
might have a very high percentage of failures because few queries
were sent to the name server during the monitoring interval; even
a short network interruption would severely impact the calculations.
If this situation repeats itself, an overly aggressive UNRESPONSIVETHRESHOLD
value might be contributing to the situation. Consider increasing
the setting value for the UNRESPONSIVETHRESHOLD parameter in the resolver
setup file and instruct the operator to issue the MODIFY  RESOLVER,REFRESH,SETUP=setup_file_name command
to make the resolver less sensitive to name server response failures.

User response
 Not applicable.

Problem determination
 Not applicable.

Source
 z/OS® Communications
Server TCP/IP: System Resolver

Module
 EZBRENSR

Routing code
 2, 8

Descriptor code
 2

Automation
 Candidate for automation. The automation can alert
the network operator of the condition, or it can trigger processing
to collect diagnostics related to  the name server.

Example
  EZZ9311E STOPPED USING NAME SERVER AT IP ADDRESS 10.45.23.200