As most people would know, changing the TOD clock on a mainframe is fraught
with difficulties.  z/OS uses TOD timestamps all over the place to manage
change and consistency, not the least being LRSN's for DB2 and IMS
logging.  Changing the TOD clock forward in time can cause problems,
changing it backward in time is absolutely forbidden.

So switching the TOD clock from local time to GMT for any CEC east of
Greenwich requires moving the TOD clock backwards.  So, for many years,
IBM's standard advice for Australian sites was to take a 10-hour
sysplex-wide outage.  Understandably, most sites continued with a TOD clock
set to local time.

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.

Matthew

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