Applying this set up information to z/OS Explorer

As stated before, z/OS® Explorer is dependent upon TCP/IP having the correct hostname when it is initialized. This implies that the different TCP/IP and Resolver configuration files must be set up correctly.

The following example focuses on some configuration tasks for TCP/IP and Resolver. Note that this does not cover a complete setup of TCP/IP or Resolver, it just highlights some key aspects that might be applicable to your site:

In the following JCL, you can see that TCP/IP will use SYS1.TCPPARMS(TCPDATA) to determine the stack’s hostname.

//TCPIP    PROC PARMS=’CTRACE(CTIEZB00)’,PROF=TCPPROF,DATA=TCPDATA
//*
//* TCP/IP NETWORK
//*
//TCPIP    EXEC PGM=EZBTCPIP,REGION=0M,TIME=1440,PARM=&PARMS
//PROFILE  DD  DISP=SHR,DSN=SYS1.TCPPARMS(&PROF)
//SYSTCPD  DD  DISP=SHR,DSN=SYS1.TCPPARMS(&DATA)
//SYSPRINT DD  SYSOUT=*,DCB=(RECFM=VB,LRECL=132,BLKSIZE=136)
//ALGPRINT DD  SYSOUT=*,DCB=(RECFM=VB,LRECL=132,BLKSIZE=136)
//CFGPRINT DD  SYSOUT=*,DCB=(RECFM=VB,LRECL=132,BLKSIZE=136)
//SYSOUT   DD  SYSOUT=*,DCB=(RECFM=VB,LRECL=132,BLKSIZE=136)
//CEEDUMP  DD  SYSOUT=*,DCB=(RECFM=VB,LRECL=132,BLKSIZE=136)
//SYSERROR DD  SYSOUT=*

SYS1.TCPPARMS(TCPDATA) tells you that you want the system name to be the hostname and that you do not use a domain name server (DNS); all names will be resolved through site table lookup.

; HOSTNAME specifies the TCP host name of this system.  If not
; specified, the default HOSTNAME will be the node name specified
; in the IEFSSNxx PARMLIB member.
;
; HOSTNAME
;
; DOMAINORIGIN specifies the domain origin that will be appended
; to host names passed to the resolver.  If a host name contains
; any dots, then the DOMAINORIGIN will not be appended to the
; host name.
;
DOMAINORIGIN  RALEIGH.IBM.COM
;
; NSINTERADDR specifies the IP address of the name server.
; LOOPBACK (14.0.0.0) specifies your local name server. If a name
; server will not be used, then do not code an NSINTERADDR statement.
; (Comment out the NSINTERADDR line below).  This will cause all names
; to be resolved via site table lookup.
;
; NSINTERADDR  14.0.0.0
;
; TRACE RESOLVER will cause a complete trace of all queries to and
; responses from the name server or site tables to be written to
; the user’s console.  This command is for debugging purposes only.
;
; TRACE RESOLVER

In the Resolver JCL you see that the SETUP DD statement is not used. As mentioned in Understanding resolvers, this means that GLOBALTCPIPDATA and other variables will not be used.

//RESOLVER PROC PARMS=’CTRACE(CTIRES00)’
//*
//* IP NAME RESOLVER – START WITH SUB=MSTR
//*
//RESOLVER EXEC PGM=EZBREINI,REGION=0M,TIME=1440,PARM=&PARMS
//*SETUP    DD  DISP=SHR,DSN=USER.PROCLIB(RESSETUP),FREE=CLOSE

If you assume that the RESOLVER_CONFIG environment variable is not set, you can see in Table 1 that Resolver will try to use /etc/resolv.conf as base configuration file.
```
TCPIPJOBNAME TCPIP
DomainOrigin RALEIGH.IBM.COM
HostName CDFMVS08
```
As mentioned in Search orders used in the z/OS UNIX environment, the base configuration file contains TCPIP.DATA statements. If the system name is CDFMVS08 (TCPDATA stated that the system name is used as hostname) you can see that /etc/resolv.conf is in sync with SYS1.TCPPARMS(TCPDATA). There are no DNS definitions so site table lookup will be used.
Table 1 also tells you that if you do not have to do anything to use the default ASCII-EBCDIC translation table.
Assuming that the TSO MAKESITE command is not used (can create the X_SITE and X_ADDR variables), /etc/hosts will be the site table used for name lookup.
```
#  Resolver /etc/hosts file cdfmvs08
9.42.112.75   cdfmvs08                     # CDFMVS08 Host
9.42.112.75   cdfmvs08.raleigh.ibm.com     # CDFMVS08 Host
127.0.0.1     localhost
```
The minimal content of this file is information about the current system. In the preceding sample, both cdfmvs08 and cdfmvs08.raleigh.ibm.com are defined as a valid name for the IP address of the z/OS system.

If you were using a domain name server (DNS), the DNS would hold the /etc/hosts info, and /etc/resolv.conf and SYS1.TCPPARMS(TCPDATA) would have statements that identify the DNS to your system.

To avoid confusion, you should keep the TCP/IP and Resolver configuration files in sync with each other.

Table 1. Local definitions available to resolver
File type description	APIs affected	Candidate files
Base resolver configuration files	All APIs	GLOBALTCPIPDATA RESOLVER_CONFIG environment variable /etc/resolv.conf SYSTCPD DD-name userid.TCPIP.DATA jobname.TCPIP.DATA SYS1.TCPPARMS(TCPDATA) DEFAULTTCPIPDATA TCPIP.TCPIP.DATA
Translate tables	All APIs	X_XLATE environment variable userid.STANDARD.TCPXLBIN jobname.STANDARD.TCPXLBIN hlq.STANDARD.TCPXLBIN Resolver-provided translate table, member STANDARD in SEZATCPX
Local host tables	endhostent endnetent getaddrinfo gethostbyaddr gethostbyname gethostent GetHostNumber GetHostResol GetHostString getnameinfo getnetbyaddr getnetbyname getnetent IsLocalHost Resolve sethostent setnetent	IPv4 X_SITE environment variable X_ADDR environment variable /etc/hosts userid.HOSTS.xxxxINFO jobname.HOSTS.xxxxINFO hlq.HOSTS.xxxxINFO IPv6 GLOBALIPNODES RESOLVER_IPNODES environment variable userid.ETC.IPNODES jobname.ETC.IPNODES hlq.ETC.IPNODES DEFAULTIPNODES /etc/ipnodes

Note: Table 1 is a partial copy from a table in Communications Server: IP Configuration Guide (SC31-8775). See that manual for the full table.