We had the time steering function using sysplex timers. I believe that the maximum time that could be steered was one minute, which took days/weeks to accomplish. If you needed more than a minute, you had to start the process again. STP raised the limit that could be set, but didn't speed it up any.
Mark Jacobs Sent from ProtonMail, Swiss-based encrypted email. GPG Public Key - https://api.protonmail.ch/pks/lookup?op=get&[email protected] ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Monday, September 21, 2020 7:00 PM, Paul Gilmartin <[email protected]> wrote: > On Tue, 22 Sep 2020 07:35:44 +1000, Matthew Donald wrote: > > > A few years ago (z14 announcement??), IBM announced a new PR/SM feature > > which would decrement the TOD clock 1 second at a time, while > > simultaneously incrementing the timezone offset. Can anyone shine any > > light on this feature? I've searched through the HMC manuals without any > > luck - a pointer to documentation would be greatly appreciated. > > But that leaves a hazard for a job that fetches CVTLDTO before the STCK(E); > less so for the job that does the STCK(E) first. But it's possible to steer > the clock (but only by a couple seconds a day). I assume the hardware > guarantees uniqueness of STCK, and incrementing CVTLDTO introduces > no hazard. > > I believe the hardware steering feature is much older than z14. > > Several years ago, we had a TOD clock that was a couple minutes off. We > wanted to issue the command (HMC?) that would steer the clock to correct > But we were blocked by a software validity check that would not accept > such a large correction. We instructed our operator to apply the maximum > permitted correction every couple days. > > I suspect that the "z14 announcement??" might merely remove the maximum > adjustment limit. > > How does this play with OMVS? > > Does the TIME macro's SVC have code to ensure that STCK and fetch > CVTLSO don't happen on opposite sides of a leap second? > > -- gil > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
