Re: Slow Ping using Host Table

[Scott Klement <midrange-l@xxxxxxxxxxxxxxxx>]

Hi Michael,

> I have tested a number of application calls and they are all running
> slowly, a simple test I made was pinging the servers using the name
> reference from the table -  each took 16 sec and Ping using the IP
> address (instantaneous).  There have been no changes to the OS a
> number on months, and no PTF's have been applied.

When you say that the PING takes 16 seconds, are you saying that you get a
message like the following?

  PING reply 1 from 192.168.0.1 took 16 sec. 256 bytes. TTL 64.

Or are you saying that it takes 16 seconds for PING to even start up?
(But then once it gets going, the speeds are normal)

If it's the former, then the problem can't possibly be related to the host
table or name resolution. The name resolution is completed before
the ping packet is sent out, and so it's not a part of the time that PING
reports.

If you're suggesting that the problem is, indeed, a name resolution
problem then please make certain that your iSeries is checking the host
table BEFORE attempting to talk to a DNS server.

If you type the following at the command prompt:
  ?CHGTCPDMN

It should show something like this:

                       Change TCP/IP Domain (CHGTCPDMN)

Type choices, press Enter.

Host name  . . . . . . . . . . .   'youriSeries'
Domain name  . . . . . . . . . .   'example.com'

Domain search list . . . . . . .   *DFT

Host name search priority  . . .   *LOCAL        *REMOTE, *LOCAL, *SAME
Domain name server:
  Internet address . . . . . . .   '192.168.0.2'

The important bit is the "Host name search priority."  If it's set to
*REMOTE it'll try doing a DNS lookup.  If the DNS lookup fails (or times
out!) then it'll check the host table.

If it's set to *LOCAL, then it'll first check the host table and only go
to DNS if that fails.

I suspect that yours is set to *REMOTE -- and the delay you're seeing is
the time it takes for DNS to time out.  If so, changing it to *LOCAL may
help. (I'm at a loss as to why you'd ever want to set it to *REMOTE!)

Possibly the DNS server that it's talking to has gone down, causing the
delay to get much longer in recent days.