Admin Alert: Updating Your System i5 for Daylight Saving Time Changes
January 24, 2007 Joe Hertvik
In the Energy Policy Act of 2005, Congress changed Daylight Saving Time (DST) in the United States so that starting this year (2007) DST begins three weeks earlier than it did last year, on the second Sunday of March. Conversely, 2007 will also see Daylight Saving Time end one week later than last year, on the first Sunday in November. This week, I’ll talk about how this change affects i5 shops.
The new DST starting and ending dates are causing some minor concerns for system i5 shops because, like the rest of the computing world, i5/OS needs to be patched so that DST changes will once again automatically occur on the correct day. There are two ways to handle this change. You can do a manual adjustment or you can apply IBM’s new Daylight Saving Time PTFs for i5 systems running i5/OS V5R3 and V5R4. There are no PTFs for pre-V5R3 and older OS/400 systems because (believe it or not) IBM did not add support for Daylight Saving Time until V5R3. If you’re working in a pre-V5R3 shop, you’ll have to implement DST the old-fashioned way: by manually updating the time of day system value (QTIME) to one hour earlier or later on the proper date.
Automatically Changing DST Values Via PTF
Here are the PTFs that IBM specifies that you download and apply to update your DST rules for each system:
According to IBM’s System i Globalization Web site (which lists out i5/OS DST updates), the PTFs automate the changes needed to support the new DST rules. After application, all of the time zone rules on the system will be updated to the new DST starting and ending dates. The PTFs are also designated to be immediate PTFs, and in many (but not most) cases they can be applied without an IPL. So as designed, they are fairly easy to apply, but there are a few things to watch out for that may force you to do more work than you intended.
First, the no-IPL application setup will not work for everyone. While the DST IPLs themselves are immediate, they may require other pre-requisite PTFs to work. When I downloaded my V5R3 PTFs, IBM also included PTF SI24910 in the batch, which requires an IPL to be applied. Depending on what other fixes you apply with the DST PTFs, you may need to IPL your system before the second Sunday in March if you want these changes to work. For shops that are several cumulative PTF groups behind, it’s almost guaranteed that you will need to IPL your box to activate the DST changes.
Depending on the time zone description that you are using for your partition, there are some instances where the PTFs will not automatically update your i5 partition’s DST rules. If your shop is running under Central Standard Time Zone QN0600S, for example, the PTFs will not change the DST start and stop times for your partition. IBM’s rule on this is that the automatic PTF update will update and change the Time Zone system value (QTIMZON) and DST information on your system, if:
After applying the PTF upgrade, you can check to see if the fix has been applied by performing the following steps on all your upgraded partitions:
1. Double-check the Time Zone description that your partition is using by referencing the QTIMZON system value. On a 5250 green screen, you can check this value by using this Display System Value command (DSPSYSVAL).
Be aware that the PTFs may have changed the default time zone value listed in QTIMZON. For example, one of my partitions was using the QN0600CST time zone before the PTFs were applied; the upgrade program changed that value to the new QN0600CST2 time zone after application.
2. Look up the Daylight Saving Time start and end date for your time zone value by using the Work with Time Zone Descriptions command (WRKTIMZON). Run this command to display all Time Zone descriptions on your system, like this:
The Work with Time Zone Descriptions screen will display all the different time zones that are defined on your system.
To find your QTIMZON time zone on the WRKTIMZON screen, page down the list until you see either the time zone listed in QTIMZON or a time zone with a greater than sign (>) in front of it (the default time zone will always be designated in this list by a ‘>’ sign). Place a 5=Display details in front of your default time zone entry and press Enter. On the screens that follow, you will see the starting and ending DST dates for your time zone description. What you are interested in is whether or not the PTFs changed your time zone DST start and end dates correctly. If your time zone rule could not be changed by the PTF upgrade (as explained above), then you should change it manually by entering the following Change Time Zone Description command (CHGTIMZON) and pressing the F4 key.
Locate the DST start and end dates on the second CHGTIMZON screen (which can be accessed by pressing the F24=More key on the first screen, followed by the F9=All key). If your time zone DST dates were not changed, you can change them manually from this screen. For 2007, enter the following values into the your time zone’s Daylight Saving Time start (DSTTSR) and Daylight Saving Time end (DSTEND) parameters:
Daylight Saving Time start: DSTSTR Month = *MAR Day = *SUN Relative day of month = 2 Time = '02:00:00' Daylight Saving Time end: DSTEND Month = *NOV Day = *SUN Relative day of month = 1 Time = '02:00:00'
These parameters are self-explanatory except for the Relative day of month value, which merely refers to whether the change will occur on the first, second, third, fourth, or *LAST Sunday of the month.
Manual Changing DST Time Zone Values
If you forget or aren’t able to download and install the DST PTFs before the daylight saving time changes occur, you can also change the DST start and end dates manually as shown in the last section. I’m not sure if IBM will support manual changes without applying PTFs, but the manual technique might work for you in a pinch. The only kicker is that, as you apply future cumulative PTFs or upgrade the system, the DST PTF upgrade may be applied at that time.
Not Just the United States, Not Just i5/OS
It should also be noted that the United States isn’t the only one changing their DST time structure. Western Australia’s Parliament has also passed new regulations regarding how Daylight Saving Time is implemented in that state. For Western Australian readers, please note that IBM has included a *TIMZON rule update that covers down under DST changes.
You should also be aware that i5/OS isn’t the only operating system item that needs a daylight savings time patch. In addition to the operating system PTFs, you should also download the following PTFs, as necessary.
IBM has upgraded i5/OS Java to support the new DST change dates. To activate its new Java support, download and install these PTFs.
If you’re using i5/OS Java Development Kit (JDK) 1.3.1, be sure to download and apply these PTFs:
For JDK 1.4.2, download and apply these PTFs:
For JDK 1.5.0, please apply these PTFs:
Additional PTFs are available for DST updates in Unicode support (SI25399 for i5/OS V5R3M0 and SI25400 for i5/OS V5R4M0) and you can check the Hardware Management Console (HMC) Daylight Saving Time Web page for information on how to upgrade an HMC for the new changes.