The following steps should be taken to determine why a "hostname
cannot be resolved" type or problem has occurred:
Note: Although you
might find the hostname through PING or NSLOOKUP commands, you might
not be able to find it through the resolver. Take the following steps
to determine why a "hostname" cannot be resolved.
- To determine the hostname returned for the IBM zAware server
location, issue the following command on the logical partition where
the IBM zAware server
runs:
hostname -g
to determine the hostname returned
for the IBM zAware server
location.If this is the hostname you expect, then skip the remainder
of this section and go to the next step.
The TCPIP started task
determines its host name when it is started by calling a service to
retrieve the value of the stack's TCPIP.DATA HOSTNAME statement.
The z/OS® UNIX search
order is used to find the stack's TCPIP.DATA statements. The host
name is determined in the following order:
- If the found TCPIP.DATA contains a valid HOSTNAME statement, its
value is returned.
- If there is no valid HOSTNAME statement, the VMCF node name with
which VMCF was started is returned.
- If VMCF was not active when the stack was started, the CVTSNAME
value (this is the SYSNAME=value in IEASYSxx that was IPLed) is returned.
If the host name came from TCPIP.DATA, it is in the message
case it was specified on the HOSTNAME statement. For VMCF or CVTSNAME
the name is upper case. If you cannot determine why TCPIP has the
wrong name, add a SYSTCPTT DD to the TCPIP proc and restart TCPIP.
This will enable resolver tracing of TCPIP.
When you fix the
hostname issue, TCPIP will have to be recycled to pick up this change.
- If the hostname is correct and it does not resolve to a valid
IP address, do the following:
Issue:
host hostname
from
where z/OS system logger runs
and make sure the
hostname resolves properly.
If
you get an error that the host is unknown, (for example: EZZ8342I
junk: Unknown host), check to see if the hostname has been added to
the DNS.
If the hostname has been added to the DNS and the name
still does not resolve to an IP address, then enable a resolver trace
for the OMVS session and issue the host command again:
Export RESOLVER_TRACE= stdout
host host-name
If you make any changes to the DNS or local
host file, you need to refresh the resolver.
- If the ip address does not resolve to a fully qualified domain
name, use the following command to verify that a fully qualified domain
name is returned and it is the fully qualified domain name expected
for the z/OS IBM zAware log
stream client:
host <ip_address>
where <ip_address>
is the ip address the host command returned in prior steps.Ensure
that this resolves to the expected hostname.
Note: If
you make any changes to the DNS or local host file, you need to refresh
the resolver.