Is the SE clock update you describe performed on z9's? We did a POR a couple weeks ago and the clock was off by about 27 minutes afterwards. I t didn't get caught for a while. The z/OS images now have their TOD prompt re-enabled and the POR instructions now include a step to check the SE
clock for accuracy. I assumed it was off due to the drift in the SE clocks since the last POR several years ago. Brian Nielsen On Mon, 1 Aug 2011 14:25:55 -0400, Alan Altmark <alan_altm...@us.ibm.com> wrote: >To reset the z/VM clock to match the CEC time, deactivate the LPAR and >reactivate it. At that time the LPAR epoch [delta from CEC TOD] will be >reset to zero, assuming it hasn't been set to a non-zero value in the LP AR >image profile. > >The System z TOD clock is the best clock in the CEC; a precision timepie ce >that even detects and adjusts for its own drift (up to a point). If you >have STP or ETR, then the TOD clock is also accurate. In that respect, >Sir Rob's point about using your wristwatch as a time reference is on >point. > >The SE historically syncs its standard PC battery operated clock (BOC) t o >the CEC TOD every 24 hours. The BOC instantly moves forward or backward . >Why bother? Because at POR, the only time reference is the SE BOC -- th e >CEC TOD will be set to that value. Once accurately set, the time on the >CEC is better since it has comparatively little drift. > >Starting the z196 GA2 upgrade and the z114: >o The SE BOC will sync to the CEC TOD once an hour instead of once a day , >improving CEC TOD accuracy after POR. >o The SE BOC will be steered the match the CEC TOD instead of making lar ge >jumps, avoiding a Paradox that could destroy the universe. >o OK, so there's no Paradox, but there are NTP-using firmware components >in a zBX environment that benefit from the steering > >You still need STP to have *accurate* time. > >Alan Altmark
