UNRESPONSIVETHRESHOLD statement

Use the UNRESPONSIVETHRESHOLD statement to specify the threshold value for when the resolver name server monitoring function declares a DNS name server to be unresponsive to resolver queries, and to specify whether the resolver should automatically stop using unresponsive name servers for Domain Name System (DNS) queries generated by an application. For detailed information about the name server monitoring function and about selecting an appropriate value for UNRESPONSIVETHRESHOLD, see the information about monitoring the responsiveness of Domain Name System name servers in z/OS Communications Server: IP Configuration Guide.

Parameters

percentage_of_queries

The threshold value for determining when the resolver declares a DNS name server to be unresponsive. The threshold represents a percentage of failures within a specific time interval. The duration of the time interval depends on the setting of the AUTOQUIESCE operand:

• If you do not specify the AUTOQUIESCE operand, the resolver monitors name server responsiveness using sliding 5-minute intervals.
• If you specify the AUTOQUIESCE operand, the resolver monitors name server responsiveness using 30-second intervals.

Valid values for percentage_of_queries are in the range 0-100.

The value 0 indicates that the resolver should not monitor name server responsiveness.

The default percentage depends on the setting of the AUTOQUIESCE operand:

• If you do not specify the AUTOQUIESCE operand, the default percentage value is 25% of resolver queries.
• If you specify the AUTOQUIESCE operand, there is no default percentage. You must specify a percentage value when specifying the AUTOQUIESCE operand.

AUTOQUIESCE

Indicates what actions the resolver takes when it identifies an unresponsive name server.

• If you do not specify the AUTOQUIESCE operand and a name server fails to respond to a percentage of resolver queries that is equal to or greater than the specified threshold level, the resolver displays message EZZ9308E to the operator console to indicate that the name server has been unresponsive for this latest 5-minute interval. The resolver continues to forward DNS queries generated by an application to the name server whether it is responsive or not. The name server is considered to be unresponsive until the percentage of queries that the name server does not respond to is less than the specified threshold, or until monitoring is disabled.
• If you specify the AUTOQUIESCE operand and a name server fails to respond to a percentage of resolver queries that is equal to or greater than the specified threshold level, the resolver displays message EZZ9311E to the operator console to indicate that the name server has been unresponsive for this latest 30-second interval. The resolver stops sending DNS queries generated by an application to the name server while the name server is unresponsive. While a name server is unresponsive, the resolver periodically sends DNS polling queries to the name server. The name server is considered to be unresponsive until the percentage of DNS polling queries that the name server does not respond is less than the specified threshold, or until the monitoring is disabled. In most cases, a minimum of 10 DNS polling queries must be attempted before the resolver considers a name server to be responsive.

  Result: If all name servers specified in the global TCPIP.DATA file are unresponsive, the resolver sends DNS queries generated by an application to those name servers, rather than failing the DNS query immediately.

The AUTOQUIESCE operand is used only when the percentage_of_queries value is greater than 0.

If you specify the AUTOQUIESCE operand, you must also code the GLOBALTCPIPDATA statement. If you do not code the GLOBALTCPIPDATA statement, the resolver issues message EZD2036I and ignores the AUTOQUIESCE operand. If you cannot ensure that all DNS IP addresses are accessible from all of your TCPIP stacks, you should not use a global TCPIP.DATA file and you should not code AUTOQUIESCE on the UNRESPONSIVETHRESHOLD setup statement in your resolver setup file. See GLOBALTCPIPDATA statement for details on coding the GLOBALTCPIPDATA statement.

The default setting is that AUTOQUIESCE is not specified.

Steps for modifying

You can refresh this statement using the MODIFY command. To modify the threshold value, the setting of the AUTOQUIESCE operand, or both, perform the following steps:

1. If you do not have a resolver setup file, create one.
2. Specify the percentage value and the required setting for the AUTOQUIESCE operand on the UNRESPONSIVETHRESHOLD statement in the resolver setup file. The following guidelines apply when you modify the value for the UNRESPONSIVETHRESHOLD statement:
   • If you change the value to 0, the function is disabled, all accumulated statistics are deleted, and any unresponsive name server notification messages are cleared from the operator console.
   • If you change the value to a nonzero value but you do not change the value of the AUTOQUIESCE operand, the new threshold percentage will be used when the next time interval ends.
     • If you do not specify the AUTOQUIESCE operand and the resolver was already monitoring name server responsiveness, existing statistics that were accumulated during the 1-minute interval are not affected and current EZZ9308E unresponsive name server messages remain on the operator console.
     • If you specify the AUTOQUIESCE operand and the resolver was already monitoring name server responsiveness, existing statistics that were accumulated during the 30-second interval are not affected and current EZZ9311E unresponsive name server messages remain on the operator console.
   • If you change the value of the AUTOQUIESCE operand, all accumulated statistics are deleted and any unresponsive name server messages (EZZ9308E or EZZ9311E) are cleared from the operator console. The resolver uses the specified threshold percentage when the next time interval (5-minutes or 30-seconds) ends.
3. Issue the MODIFY RESOLVER,REFRESH,SETUP=setup_filename command to cause the resolver to use the new threshold value, the AUTOQUIESCE operand setting, or both.

For more information about parameters used with the MODIFY command, see z/OS Communications Server: IP System Administrator's Commands .