RESOLVERUDPRETRIES statement

Use the RESOLVERUDPRETRIES statement to specify the number of times (including retries) the resolver should try to connect to the name server when using UDP datagrams.

Syntax


                     .-RESOLVERUDPRETRIES 1------.   
>>-+--------------+--+---------------------------+-------------><
   '-system_name:-'  '-RESOLVERUDPRETRIES--limit-'

Parameters

system_name:: The name of the system to which this statement applies. See system_name considerations for a complete description of this parameter.
Requirement: The colon is required.
limit: The maximum number of times the resolver should try to connect to the name server. The default is 1; the maximum number can be 2 147 483 647.

Steps for modifying

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

Examples

To specify 2 as the number of times the resolver tries to connect to the name server when using UDP datagrams, use the following code:

RESOLVERUDPRETRIES 2

Usage notes

This statement applies only when using UDP datagrams. See RESOLVEVIA statement for more information.
The resolver attempts to contact each of the specified name servers before attempting any retries.
The maximum amount of time for each UDP resolution is the product of the number of name servers (NSINTERADDR/NAMERSERVER statements) multiplied by the resolver timeout value (RESOLVERTIMEOUT statement) multiplied by the number of times to try the name servers (RESOLVERUDPRETRIES statement). This amount of time can occur for each domain name specified by the SEARCH statement. If a getaddrinfo API call is issued to request a query for both IPv4 and IPv6 addresses, the maximum amount of time can be doubled.
A RESOLVERUDPRETRIES value of zero indicates that the resolver should not attempt to contact any name servers.
Use the DIG command with the STATS option to determine how many attempts it takes for each DNS in the NSINTERADDR list to respond. Set RESOLVERUDPRETRIES to the number of attempts for the least responsive DNS in the list, and place the least responsive DNSs at the end of the list.
If network DNS response message sizes tend to be larger than 512 bytes, put name servers that support Extension Mechanisms for DNS (EDNS0) before name servers that do not support EDNS0. The z/OS® resolver supports UDP message sizes as large as 3 072 bytes when communicating with name servers that support EDNS0. Ordering the name servers in terms of EDNS0 support can potentially avoid the use of more expensive TCP protocols when processing large DNS response messages.