On Monday, 07/16/2007 at 11:21 EDT, "Little, Chris"
<[EMAIL PROTECTED]> wrote:
> Except that the line says "FORCED BY SYSTEM".  It's not just a logoff -
> although I first considered that as a possibility, but the system forced
> the guest off.
>
> I've added a "CP SET RUN ON" line to the PROFILE.EXEC in the guest.....

Shutting down the telnet connection causes the telnet server to delete the
logical device that represents your virtual machine console.  That's like
yanking the coax out of the wall or hitting the "Normal/Test" switch.  CP
gets notified and, knowing that users want to pick up where they left off,
drops the user into CP READ and ignites the fuse on the 15-minute
auto-self-destruct sequence [with no further audible warnings].  After
all, maybe you just powered off your terminal and went home.  The point
is, CP doesn't know what happened - only that your console disappeared
unexpectedly.  He's not willing to wait forever for your return, as you
are using valuable cyber-real estate.

SET RUN ON only affects what your virtual machine does while in CP READ,
not whether the "timebomb", as we affectionately call it, is triggered.
(SET RUN ON also causes an "auto-BEGIN" if you reconnect in time.)

CP SET TIMEBOMB OFF or DISCONNECT_TIMEOUT 0 are the only things that can
prevent the self-destruct.  The DISCONNECT_TIMEOUT affects how long CP
will wait.

This behavior is somewhat anachronistic, not differentiating between
physical devices and LDEVs, and trying to protect the precious 16MB of
available memory!  IMO, you can safely turn it off if you are in the Linux
guest business.  If you still have lots of CMS users, then it may be best
to leave it in place, depending on whether your user population has been
properly disciplined over the years.  (I know that users can be difficult
to housebreak.  ;-) )

In z/VM 5.3 I believe you can connect to the *VMEVENT system to watch for
guests that enter (and leave!) this state, taking proactive measures as
needed.  (SET SECUSER * , SEND BEGIN)

Alan Altmark
z/VM Development
IBM Endicott

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