Re: Daylight Savings time

[Chris Whisonant <Chris.Whisonant@xxxxxxxxxxxxx>]

Thanks - we can't say we weren't warned. I'll have to bounce the server to 
make sure we're good. I've been bitten by this in the past...  =)

Chris Whisonant
Comporium
Senior Mid-Range Systems Administrator
IBM eServer Certified Systems Expert - iSeries Technical Solutions V5R2
IBM Certified System Administrator - Lotus Notes and Domino 6/6.5
803.326.7270 | 803.326.6142 fax
http://cwhisonant.blogspot.com/

domino400-bounces+chris.whisonant=comporium.com@xxxxxxxxxxxx wrote on 
10/07/2005 11:23:16 AM:

> Just a friendly reminder.
> 
> 
> Title  *        Managing System Time changes 
> 
> Abstract        This document describes how to Manage system time 
changes 
> due to Daylight Savings Time on OS/400 V5R3 and V5R2. 
> 
>    Cause           Domino on iSeries cannot manage a system time change 
> while active
> 
> Content/Solution 
> ALERT: ANY change in system time while a DOMINO server is active will 
> impact Server performance. The larger the time change the larger the 
> impact on performance.  DOMINO should be ended for any manual change to 
> QTIME. 
> 
> Concerns for SNTP
>         Each partition does have its own separate QTIME and QUTCOFFSET 
> values.  For Daylight Savings Time, the system values must be updated 
for 
> each partition.
>         SNTP does not update QTIME.  SNTP updates a separate clock used 
by 
> POSIX APIs.  There is no need to turn off SNTP when QTIME is changed for 

> Daylight Savings Time.
> 
>         OS/400 V5R2 
>         No native support for Daylight savings time.  When moving into 
or 
> out of DST the system value QTIME  and  QUTCOFFSET must be altered by 
the 
> system operator.
>         QTIME holds the current time value of the OS/400.
>             As DST ends QTIME would up updated from 2:00  to 1:00 
> 
>         Another consideration for changing the system time to reflect 
> daylight savings time is that of the system value Coordinated universal 
> time offset - QUTCOFFSET.  Greenwich Mean Time does not observe daylight 

> savings time so the QUTCOFFSET value must be altered to reflect the 
> difference in time caused by switching to daylight savings time.  The 
> following table shows the appropriate values to use for this system 
value 
> in the four time zones in continental USA:
> 
> 
> 
> 
> Eastern Time Zone
> Central Time Zone
> Mountain Time Zone 
> Pacific Time Zone
> Daylight Savings Time
> -4.00
> -5.00
> -6.00
> -7.00
> Standard Time
> -5.00
> -6.00
> -7.00
> -8.00
> 
>         As DST ends QUTCOFFSET would be updated by adding 1 hour to the 
> existing value (see chart above).
> 
> 
>         OS/400 V5R3
>               Can use the same solution as V5R2 but also has this 
> alternate option.
>         Time maintenance application.
>                 This application will slow or speed the clock so no 
"time 
> change" is required.  The system clock is either sped up or slowed to 
> complete the desired time change. This tool is used on systems with 
> applications which cannot permit duplicate time stamps which might occur 

> by altering the system time. While Domino is not one of these 
applications 
> the system Domino is hosted on might have one of this time sensitive 
> applications requiring the use of this tool.
> 
>         This application relies on a new OS/400 system value QTIMZON
>         If this application is used the Time is not CHANGED  the QTIME 
> system clock is either slowed or sped to meet the time change. 
> 
>         Time maintenance application 
>         Identifies the software to use to adjust the system clock to 
keep 
> it synchronized with an external time source. This system value does not 

> enforce the software specified, it only identifies the software to use. 
> This value should be maintained by time adjustment software and is 
> intended as an aid to prevent having multiple time adjustment 
applications 
> conflict with each other. There are no checks performed by the system to 

> verify this value or that software is or is not performing time 
> adjustments. IBM time adjustment offerings will use identifiers that 
start 
> with QIBM such as 'QIBM_OS400_SNTP'. Other software suppliers should 
> follow a similar naming convention of company name and product name. 
>         Time adjustment software should check this system value prior to 

> starting. If this system value has an identifier for other time 
adjustment 
> software, then the software being started should notify the user of this 

> potential conflict and confirm that this time adjustment software should 

> be started. When there is not an identifier associated with this system 
> value, the software should update this system value to identify that it 
is 
> now responsible for adjusting the system clock. Time adjustment software 

> should check this system value again prior to ending. This system value 
> should be set to the value None only if the current value identifies 
this 
> time adjustment software that is ending. 
>         Possible values are the following: 
>         None
> Indicates that time adjustment software has not been identified. 
>         identifier
> Identifies the software that will be used to adjust the system clock. 
>         For more information about the SNTP client time maintenance 
> application that IBM supplies with the system, see the iSeries 
information 
> center.
> 
> Topic   Administration
> 
> Walter Scanlan 
> Senior Software Engineer
> Domino & Workplace for iSeries
> 507-286-6088
> wscanlan@xxxxxxxxxx
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