On 2015-10-28 19:12, Timothy Sipples wrote: > > A leap second "spin" is one *option* customers have. It's not a > requirement. The other option available is ... gradual steerage to adjust > for the leap second! It takes approximately 7 hours for the IBM z System > and z/OS to smooth out one leap second. Refer to IBM Tech Doc # WP102081 > for more information: > > https://www.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP102081 > Thanks. I hadn't been aware of option 2 (that Tech Doc is a mere 4 months old.)
> So, unlike Google and Amazon, *you* choose. If you want precise timing at > every moment, choose that option (not available with Google and Amazon). If > you want gradual steerage, choose that. Unlike Google and Amazon, IBM does > not force one choice on its customers here. And you can change your mind > before the next leap second if you wish. > Choice isn't always a good thing. The saying, "The wonderful thing about standards is you have so many to choose among!" is intended sarcastically. And: https://www.ted.com/talks/barry_schwartz_on_the_paradox_of_choice?language=en And the Tech Doc doesn't address the Google/Amazon practice of *centering* the steering on the leap second, so they're never over a half second away from UTC. > Come to think of it, there's probably a third option: do whatever you want > on your external time reference, ... > OK. RYO. You could do it that way. Or perhaps use Google as the ETR source: one standard fewer. (Amazon steers for 24 hours; Google for 20.) UTC is an unfortunate choice for IT; UT1 would have been less disruptive, thus wiser. Inertia precludes a repair. Looking for a round number, a second in 7 hours is very close to 40 ppm. But that must also compensate for any intrinsic error in the CPU's crystal (? I guess. OCO?) clock. Suppose that internal reference is 10 ppm fast (still better than Timex. Is there a spec for this?) In that case, the effective steering rate is 30 ppm, and it will take about 9 hours rather than 7. Thanks again, gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
