Steps for creating a resolver setup file

The SETUP DD statement in the start procedure for the resolver points to the resolver setup file. The setup file can be an MVS™ data set or a z/OS® UNIX file.

Procedure

Perform the following steps to create a resolver setup file:

  1. Use an MVS data set or a z/OS UNIX file for your setup file, depending on your requirements.
  2. Customize the search order that the resolver uses to resolve queries by specifying one or more of the following statements:
    • Specify the GLOBALTCPIPDATA statement to identify the global TCPIP.DATA file that becomes the first file that is searched. Parameters that you specify in this file become the global settings for the entire MVS image and for all users of resolver services, across the entire system.
      Restriction: You must code the GLOBALTCPIPDATA statement if the AUTOQUIESCE operand is coded on the UNRESPONSIVETHRESHOLD statement. If you cannot ensure that all DNS IP addresses are accessible from all 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. For more information about the UNRESPONSIVETHRESHOLD statement, see z/OS Communications Server: IP Configuration Reference.
    • Specify the DEFAULTTCPIPDATA statement to identify a default TCPIP.DATA file. The file specified by the DEFAULTTCPIPDATA statement becomes the last file that can be searched. If you do not specify the DEFAULTTCPIPDATA statement, the default file is TCPIP.TCPIP.DATA.
    • Specify either the GLOBALIPNODES statement or the DEFAULTIPNODES statement to identify a local host file. The GLOBALIPNODES statement identifies a local host file that contains hard-coded IP addresses and host names that can be used globally. The DEFAULTIPNODES statement identifies the default local host file.
      Result: You can specify both the GLOBALIPNODES statement and the DEFAULTIPNODES statement, but the resolver search order for local host files ensures that only the global IPNODES file is used. For more information, see Search orders used in the z/OS UNIX environment and Search orders used in the native MVS environment.
    • Specify the COMMONSEARCH statement or the NOCOMMONSEARCH statement. The COMMONSEARCH statement indicates that the same search order for local host files is used for both IPv4 and IPv6 name queries, and for MVS and UNIX searches. The NOCOMMONSEARCH statement indicates that different search orders for local host files are used for IPv4 and IPv6 name queries, and for MVS and UNIX searches. For more information, see Search orders used in the z/OS UNIX environment and Search orders used in the native MVS environment.
    • Specify the CACHE statement or the NOCACHE statement. The CACHE statement enables system-wide caching of Domain Name System (DNS) queries that have been resolved. System-wide caching is enabled by default, but you can explicitly enable it using this statement. See Resolver caching for more information about caching. The NOCACHE statement indicates that you do not want to cache DNS response data.
      • If you are using system-wide caching, specify the CACHESIZE statement to define the amount of storage that can be allocated by the resolver to manage cached records. If you specify this statement and the NOCACHE statement, the CACHESIZE statement is ignored.
      • If you are using system-wide caching, specify the MAXTTL statement to define the amount of time that the resolver can use resource information that it receives from a name server. If you specify this statement and the NOCACHE statement, the MAXTTL statement is ignored.
    • Specify the UNRESPONSIVETHRESHOLD statement to define the threshold value that is used by the resolver to declare that a DNS name server is unresponsive. The monitoring of unresponsive name servers is enabled by default, but you can explicitly enable it using the UNRESPONSIVETHRESHOLD statement. In addition to specifying the threshold value, use the UNRESPONSIVETHRESHOLD statement to indicate how you want the resolver to react when an unresponsive name server is detected:
      • Specify only the threshold value on the UNRESPONSIVETHRESHOLD statement to indicate that the resolver should only alert the operator that a name server is unresponsive. The resolver will continue to send DNS queries that are generated by an application to the name server.
      • Specify the AUTOQUIESCE operand on the UNRESPONSIVETHRESHOLD statement to indicate that the resolver should stop sending DNS queries that are generated by an application to unresponsive name servers.
        Restriction: You must code the GLOBALTCPIPDATA statement if the AUTOQUIESCE operand is coded on the UNRESPONSIVETHRESHOLD statement. If you cannot ensure that all DNS IP addresses are accessible from all 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. For more information about the UNRESPONSIVETHRESHOLD statement, see z/OS Communications Server: IP Configuration Reference.

      If you do not want the resolver to maintain awareness of unresponsive name servers, you can use the UNRESPONSIVETHRESHOLD statement to disable resolver monitoring of name server responsiveness to DNS queries.

Results

The following example setup file is located in SEZAINST as member EZBRECNF (alias RESSETUP):

;
;   IBM Communications Server for z/OS
;   SMP/E distribution name: EZBRECNF
;
;   5694-A01 Copyright IBM Corp. 2002, 2011,
;   Licensed Materials - Property of IBM
;
;   Function: Sample Resolver setup file
;
;
;  The following statement defines the final search location for
;   TCPIP.DATA statements. It will replace TCPIP.TCPIP.DATA
;  It may be an MVS data set or HFS file.
;
DEFAULTTCPIPDATA('TCPIP.TCPIP.DATA')
;
#  The following statement defines the first search location for
#   TCPIP.DATA statements. It may be an MVS data set or HFS file.
;
;  Update with the correct data set or HFS file name
;
; GLOBALTCPIPDATA('TCPCS.SYS.TCPPARMS(GLOBAL)')
;
; GLOBALTCPIPDATA(/etc/tcpipglobal.data)
;
#  The following statement defines the first search location for
#   IPNODES statements. It may be an MVS data set or HFS file.
;
;  Update with the correct data set or HFS file name
;
; GLOBALIPNODES('TCPCS.SYS.TCPPARMS(IPNODES)')
;
; GLOBALIPNODES('TCPCS.ETC.IPNODES')
;
; GLOBALIPNODES(/etc/ipnodes)
;
#  The following statement defines the final search location for
#   IPNODES statements. It may be an MVS data set or HFS file.
;
;  Update with the correct data set or HFS file name
;
; DEFAULTIPNODES('TCPCS.SYS.TCPPARMS(IPNODES)')
;
; DEFAULTIPNODES('TCPCS.ETC.IPNODES')
;
; DEFAULTIPNODES(/etc/ipnodes)
;
#  The following statement defines if the common search order
#   should be used or not.
;
NOCOMMONSEARCH
;
; COMMONSEARCH
;
#  The following statement defines if system-wide resolver caching
#   should be used or not.
;
CACHE
;
; NOCACHE
;
#  The following statement defines the amount of storage that the
#   resolver can use for holding system-wide resolver cache data.
;
CACHESIZE(200M)
;
#  The following statement defines the maximum amount of time that
#   the resolver can use resource information that was cached as
#   a result of a query to a name server.
;
MAXTTL(2147483647)
;
#  The following statement defines the threshold value for declaring
#   a name server as unresponsive.  The AUTOQUIESCE option defines
#   whether resolver temporarily stops using unresponsive name servers.
#   You must code the GLOBALTCPIPDATA statement when you specify the
#   AUTOQUIESCE option on the UNRESPONSIVETHRESHOLD statement.
;
UNRESPONSIVETHRESHOLD(25)
;
; UNRESPONSIVETHRESHOLD(100,AUTOQUIESCE)
Parent topic: The resolver setup file