Craig Vespe wrote:
>
> Hi all -
>
> I mentioned a while back we were using SETCLOCK for year 2000 testing
> on one of our 'crash and burn' machines. There were quite a few
> people using it, both developers and support people, but somehow our
> 925 got into a curious state:
>
> S925(/SYS/PUB):showtime
> SUN, OCT 28, 1934, 4:36 AM
> S925(/SYS/PUB):showclock
>
> SYSTEM TIME: WED, APR 25, 2027, 11:00:42 PM
> [...]
>
> I'm really at a loss as to how the hardware and software clocks could
> get so out of sync. Now using SETCLOCK at the CI aborts the CI. This
> machine is still on MPE/iX X.55.20. Any clue as to how it got so
> confused (along with us)?
>
> cv
> --
> Craig Vespe [log in to unmask] Unison Software 811 Barton Springs, Austin Tx.78704
> 512-478-0611 http://www.unison.com NASDAQ UNSN disclaimer quote ANSI graphics
Hi Craig,
I can't explaine what's going on your system, but as far as I know
you have to keep in mind 4 items when altering the clocks in MPE/iX:
1. the hardware clock
2. the software clock
3. the current offset of the both above
4. the currently running time correction
By having some requests from German customers who are amazed by the
poor documentation of SETCLOCK I've written a tiny cookbock for them
which I think could help. It's for German customers but I think it's
not problem for you to adapt it for your time zone.
Regards,
Holger Wiemann, Hewlett Packard Germany
The cookbook, here we go:
How to set time/clocks on MPE/iX
------------------------------------------------------------------------
last update: 02-Dec-1996
------------------------------------------------------------------------
* There are some infos you have to know when specifying correct date
and time on a MPE/iX system. There exist two clocks and an offset:
o Hardware Clock:
Normally you have to set the hardware clock at Greenwich
Meantime (GMT) on system startup with the 'clkutil' in ISL.
o Software Clock:
To set the software clock at your local time you have to
specify it while system startup when you are prompted after
'start' command from within ISL.
o Greenwich Meantime/MPE local time Offset:
The GMT/MPE time offset is calculated as follows:
offset = software clock - hardware clock
(Values of clocks at startup of the system!)
* Most date and time routines/functions on MPE/iX are just using the
local time. But there are some exceptions using different
strategies to get the GMT:
o using hardware clock
GMT = hardware clock
I don't know any programs really doing this
o substracting offset from local time (software clock)
GMT = software clock - offset
As far as I know most subsystems needing GMT use this method.
o special calculating of local time with timezone variable 'TZ'
local time = software clock - offset + value of 'TZ'
Value of 'TZ' can be negative (in Germany it is positive!),
see next point Timezones. If in MPE environment the 'TZ'
variable has a value for which an entry exists in
TZTAB.LIB.SYS, daylight saving is taken into consideration.
Known subsystems supporting this are COBOLII/iX, C/iX Library,
SNMP/XL, Fortran 77/iX, Allbase/4GL and the POSIX/iX Shell
with libraries.
* Timezones (Western- and Eastern-Hemispheres):
The difference between soft- and hardware clock is the timezone you
use on your system. It's also equivalent to following model:
Greenwich Meantime (GMT)
|
------------------------------------------------
negative positive
deviation deviation
from GMT from GMT
(Western (Eastern
Hemisphere) Hemisphere)
In Germany we have a deviation of +1 hour from GMT, with daylight
saving this is +2 hours.
* As you can see there are some subsystems getting their local time
with timezone variable 'TZ'. Here is a very easy method the author
prefers by the simple understanding:
o Setting 'TZ' variable on MPE/iX prompt (logon UDC):
SETVAR TZ,'EST-1'
or
SETVAR TZ,'EST-2'
o Setting 'TZ' variable in POSIX/iX Shell (/etc/profile):
export TZ='EST-1'
or
export TZ='EST-2'
(This means:
o 'EST' can be any string, here it stands for Eastern
Hemisphere.
o '-' specify a deviation value in the Eastern Hemisphere.
(Leaving it out it would be in the Western one!)
o # are absolut hours of deviation from GMT)
So, 'EST-1' is the local time at Germany, 'EST-2' is daylight
saving at Germany.
Important info: If variable 'TZ' is not set, some subsystems assume
a value of 'EST5EDT' which forces to recognize daylight saving
entries for this in TZTAB.LIB.SYS! In POSIX/iX the unset of
variable 'TZ' leads to GMT0!
If you are in Germany and you don't want to doubt about of changing
'TZ' variable in MPE and POSIX-Shell when toggling daylight saving
you just have to set
SETVAR TZ,'MEZ-1MESZ'
in MPE environment and in POSXI shell
export TZ='MEZ-01:00MESZ-02:00,M3.5.0/03:00,M9.5.0/02:00'
(This looks a little bit complex but remember POSIX WILL NOT READ
MPE FILE TZTAB.LIB.SYS !!!)
In this case the correct daylight saving value in MPE environment
is read from TZTAB.LIB.SYS. You only have to change the software
clock gradually.
* Setting your correct values of hard-, software clock and timezone
gradually (this can be done on small time deviations of some
hours):
First check your current settings with SHOWCLKS.PUXL.TELESUP:
SHOWCLKS/XL A.10.00
DEBUG/iX B.79.06
HPDEBUG Intrinsic at: bd.00007258 PROGRAM+$198
PRIV=$3 := $0
*************************************************************
*** ***
*** Greenwich Mean Time : MON, APR 15, 1996, 3:26 PM ***
*** GMT/MPE offset : +1:00:00 ***
*** MPE System Time : MON, APR 15, 1996, 4:26 PM ***
*** ***
*************************************************************
**** C Library Information ****
Current value of Time Zone(TZ) variable : EST-1
CTIME function return : Mon Apr 15 16:26:36 1996
Now there are only two possible cases:
1. Greenwich meantime is set correct but MPE/local system time is
not. You only have to gradually adapt the local time with
SETCLOCK TIMEZONE (example):
SETCLOCK TIMEZONE=E02:00
(Eastern hemisphere, 2 hour deviation. Using SETCLOCK TIMEZONE
is the only command you need to toggle between set/unset of
daylight saving if hardware clock is set correct!!! Don't
forget to adapt 'TZ' variable on MPE and POSIX/iX-Shell if
necessary!!!)
2. Greenwich meantime and MPE system time are not set correct:
+ First set correct timezone (example):
SETCLOCK TIMEZONE=E02:00
(This doesn't change the hardware clock but starts a
gradually adaption of the software clock! Don't forget to
adapt your 'TZ' variable in MPE and POSIX-Shell if
necessary!!!)
+ If SHOWCLOCK shows a current running time correction of
not equal 0 (ZERO) seconds like:
SYSTEM TIME: MON, APR 15, 1996, 5:58:14 PM
CURRENT TIME CORRECTION: 3543 SECONDS
TIME ZONE: 2 HOURS 0 MINUTES EASTERN HEMISPHERE
abort this correction process with
SETCLOCK ;CANCEL
+ Now there are two possible cases:
1. The local date and time you want the system to be is
in the future of the current local time (example):
:SHOWCLOCK
SYSTEM TIME: MON, APR 15, 1996, 18:00:14 PM
CURRENT TIME CORRECTION: 0 SECONDS
TIME ZONE: 2 HOURS 0 MINUTES EASTERN HEMISPHERE
You want the system to be at 04/15/1996 19:00 h:
SETCLOCK DATE=04/15/1996;TIME=19:00:00;NOW
(Hardware- and software clock are set immediately to
correct values!)
2. The local date and time you want the system to be is
in the past of the current local time (example):
:SHOWCLOCK
SYSTEM TIME: MON, APR 15, 1996, 18:00:14 PM
CURRENT TIME CORRECTION: 0 SECONDS
TIME ZONE: 2 HOURS 0 MINUTES EASTERN HEMISPHERE
You want the system to be at 04/15/1996 17:00 h!
First correct the hard- and software clocks to
values some minutes in the future of the current
local time:
SETCLOCK DATE=04/15/1996;TIME=18:03:00;NOW
(Hardware- and software clock are set immediately to
future values!)
Second gradually smooth local date and time to
correct values:
SETCLOCK DATE=04/15/1996;TIME=17:05:00
(Hardware clock is set immediately to correct GMT
time!
Software clock is gradually set to correct local
time)
* For more infos using the file TZTAB.LIB.SYS which prevents you from
changing 'TZ' variable in MPE when toggling daylight saving see:
o HP C/iX Library Reference Manual
o HP FORTRAN 77/iX Reference
o HP COBOL II/XL Reference Manual
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