On 20 July 2012 21:53, Alan Altmark <[email protected]> wrote:

> Except for I/O timestamping, CP will not otherwise pay attention to STP
> once he has IPLed.  But even so, STP will work to keep the LPAR time in
> sync with the external time reference through "TOD clock steering."   Just
> be aware that if the time reference and the LPAR time are too far apart,
> the steering will not be enough to fix the LPAR time in a reasonable time
> period.

Hear, hear!  Could we get that engraved in a place where IBM Sales
people see it.

Ever since my presentation in 2005, I find customers who were told by
their friendly IBMer not to get STP/ETR on the machine because "it's
not supported by z/VM"  The STP/ETR feature is a priced feature that
is best negotiated into the deal early rather than acquired separately
later. When the LPAR TOD is kept in synch with the world, by pure
magic CP, CMS as well as Linux guests will see accurate time. There is
no need for ntpd in Linux (in fact, doing that will make things
worse).

The only disruptive time shift would be when you POR with the feature
on. Since the LPAR also picks up the actual time at activation, there
should not be a jump. And STP/ETR will nicely speed up TOD increments
to make it match real time. Except when the leap second meets a
software bug and takes the system down :-)

Rob

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