On 21 September 2016 at 18:40, Phil Smith <p...@voltage.com> wrote:
> I had some vague idea that on z/OS, the Resolver can use some or all of:
>
> 1.     DNS
>
> 2.     Its own configuration data sets, via GLOBALIPNODES statements
>
> 3.     /etc/hosts
>
> I just spent some time looking at IBM doc, and what I found seems to support 
> this. What I couldn't seem to grok was whether you can control the *order* in 
> which the three are used: that is, can you say "OK, we use the DNS server at 
> this IP, but we want to look in /etc/hosts *first*"?

There is a LOOKUP statement in the TCPDATA member/file.

; LOOKUP indicates the order of name and address resolution.  DNS means
; use the DNSs listed on the NSINTERADDR and NAMESERVER statements.
; LOCAL means use the local host tables as appropriate for the
; environment being used (UNIX System Services or Native MVS).

You may be able to point a particular app at its own TCPDATA (DDNAME
SYSTCPD or via the various UNIXy search orders), which in turn can
contain not only its own LOOKUP statement, but perhaps even point to a
different DNS server than the system-wide default. In particular, you
could run your own tiny DNS on the same z/OS image, perhaps listening
on a highish port so you don't run into trouble with not being allowed
to listen on a well known one. But probably this is overcomplicated.

Tony H.

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