[EMAIL PROTECTED] wrote:
Speaking in terms of Mainframes, What is "TRUE UTC" mean?
1. What does this mean??? I am still lost like crazy here...When they
speak in terms of setting the times as "TRUE UTC", do they mean the
Hardware clock (TOD) is set to UTC and the Displayed time (the desktop
clock) is set to UTC also??
I can only assume that this means you are synching your Sysplex Timers
using the external modem dialing a atomic clock instead of one of the
computer operators Timex. Either than or that you are attemting to set
your TOD clock to UTC time. If you really don't care that your time is
100% accurate you can set your TOD clock to your local time and then set
a local offset to zero. However doing this may cause you problems with
DBMS (see later on for more on this).
2. What is the proper setting of the time in Mainframes and
applications running on it? Does the TOD clock have to be set in UTC
and also the actual DISPLAYED time on the DESKTOP also have to be set
as UTC? Or, ONLY the Hardware clock (TOD) has to be set as UTC and the
applications will log time as LOCAL TIME according to the offset?? In
other words, do all applications running on the mainframes have to log
their times as LOCAL time according to the offset from the TOD clock
(which is set to UTC)?? Or, the applications are logged as UTC also??
Generally we set the TOD clock to UTC and then adjust the local time
offset for standard/daylight savings time. This allows programs that do
logging (such as DBMS's) to use the TOD clock for their logs and thus
there are no prolems for roll backs or roll forwards if something
happens during a time change. In fact some DBMS's running on the
mainframe are required to be down for 1 hour if you reset the TOD clock
backwards in the fall.
As for desktops and RTC time. Windows will display the RTC time as the
local time. Linux will allow you to set the RTC to UTC and then
configure a local offset and display the time as your local time.
Also, what is actually a TOD Clock? Is it the same as running the Real
Time Clock or the CMOS clock on home standard PCs?? Is the same as
that?
In very simple terms you can think of a TOD clock as a highly accurate
RTC/CMOS clock. Sort of like comparing your normal everyday watch to a
atomic clock. I am not 100% sure how accurate TOD clocks are (I know
that Sysplex Timer are supposed to be accurate to +/- 30 seconds a
year), but I have Windows boxes loose minutes in a day.
Thanks in advance!
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