AIX O/S updated to support 2007 Daylight Saving Time change

[ This page updated October 18, 2007 ]

October 25, 2006
The Energy Policy Act of 2005 (Public Law 109-58) was passed by the United States Congress on July 29, 2005 and signed into law on August 8, 2005. This law changes the time-change dates for Daylight Saving Time in the United States. Beginning in 2007, DST will begin on the second Sunday in March and end on the first Sunday in November. On AIX systems, the system administrator sets the DST rules for their system to follow by configuring the TZ environment variable in the /etc/environment file. If the administrator has specified that DST is observed, but no rules to select the date have been specified, then a default DST rule will be selected by the system. This default rule is set to match the DST rule for the United States.

IBM has released updates to the AIX 5L operating systems to support this change. The updates should be applied prior to March 11, 2007.

AIX 5L Version 5.3

IBM recommends installing Technology Level 4 or higher. Technology Level 4 is the minimum level that includes the DST fix, APAR IY75211. An alternative, which avoids any software update, is to manually change your DST setting as described below under "Setting your DST manually".
Filesets: bos.rte.libc.5.3.0.40 and bos.adt.prof.5.3.0.40

IY75211 is the only APAR which impacts the DST setting of the AIX operating system. However, there are other optional fixes which update some DST information located in other packages found on AIX. These include Java, zdump, WebSM, and ICU. Information on these optional updates appears in separate sections below.

AIX 5L Version 5.2

IBM recommends installing Technology Level 8 or higher. Technology Level 8 is the minimum level that includes the DST fix, APAR IY75213. An alternative, which avoids any software update, is to manually change your DST setting as described below under "Setting your DST manually".
Filesets: bos.rte.libc.5.2.0.85 and bos.adt.prof.5.2.0.85

IY75213 is the only APAR which impacts the DST setting of the AIX operating system. However, there are other optional fixes which update some DST information located in other packages found on AIX. These include Java, zdump, WebSM, and ICU. Information on these optional updates appears in separate sections below.

NOTE: If you have already updated your system to AIX 5.2 Technology Level 9 and successfully rebooted, you can disregard the rest of this note. If you are updating your AIX 5.2 system to Technology Level 9 on one of the systems listed in the table below, please ensure that you are at the listed firmware level (or later) before you perform the AIX update. This is only applicable to systems with AIX 5.2 installed; Linux on System p installations of these same models are not affected.

These firmware fixes are not DST related.

They represent the minimum level required to prevent potential booting issues associated with AIX 5.2 Technology Level 9.

If you have trouble booting your POWER4 system after updating your 5.2 system or your firmware, then you should verify and correct the value of the real-base firmware variable according to these instructions:

1. Go to the open firmware prompt when the system is booting by typing 8 when a beep is heard or the banner is seen. If applicable, the HMC can also be used to set to boot to SMS menu. From SMS menu type 0 and go to OF prompt.
2. At the prompt, type:

        printenv real-base
   

   It will display text similar to:

   -------------- Partition: common -------- Signature: 0x70 ---------------
   real-base                2000000             c00000 
   

3. Verify that the number following real-base is c00000. If it is any value other than c00000, then run this command to change it:

        setenv real-base c00000
   

   (That is the letter c followed by 5 zeroes.)
4. After updating the real-base variable, reboot system using power switch.

AIX 5L Version 5.1 (Out of support)

The update is available as a specific fix by installing APAR IY75214. An alternative, which avoids any software update, is to manually change your DST setting as described below under "Setting your DST manually".
Filesets: bos.rte.libc.5.1.0.70 and bos.adt.prof.5.1.0.70

IY75214 is the only APAR which impacts the DST setting of the AIX operating system. However, an optional fix for Java on AIX 5.1 is also available. Information on the Java update appears in a separate section below.

Setting your DST manually (to be used for out of support versions, such as AIX 4.3.3, or where the customer wants to update the system DST setting without applying any software fixes)

You can manually specify when to start and stop DST by setting the TZ environment variable in the /etc/environment file.

Examples for the four most common US timezones follows:

In the TZ variable example above, the first three characters represent the name of the timezone when not observing DST, such as "EST" for "Eastern Standard Time". The first numeral to appear reflects the number of hours behind Coordinated Universal Time (UTC); for example, EST is 5 hours behind UTC. The next three characters represent the name of the timezone when observing DST, such as "EDT" for "Eastern Daylight Time". Following the timezone names is a comma-separated rule for when the location begins and ends observance of DST:

"M3.2.0" means to begin observing DST starting in month 3 (March), week 2, and Day 0 (Sunday) = second Sunday in March. "M11.1.0" means to end observing DST on the first Sunday in November. If no DST rules are specified in the TZ variable, then the system will select the rules based on the US defaults. If a DST rule is manually specified, then the system defaults do not get used and the aforementioned APARs become unnecessary.

Since no time is specified, the default is 02:00:00 for the time change.

These correspond to the new US rules for 2007 and beyond. Once updated, the TZ environment variable will not need to be adjusted again (unless a new law changes the rules). Locations outside the US may need to set the rule to a different month or week number to reflect their own local DST observances.

More detail about setting the TZ variable can be found in the "AIX documentation for /etc/environment".

NOTE: Reboot the system before March 11, 2007 so all processes running will pick up the new time change.

zdump Databases

The zdump command can be used to display DST observance information. This information is read out of independent data files which are not used elsewhere by AIX, and unlike some other operating systems, they do not have any impact on the DST settings of the operating system. Thus, updating the zdump databases is optional. However, if you wish to make this update for consistency, you may apply the following APARS:

• AIX 5.3: Technology Level 5 is the minimum level on which to apply the DST fix, IY91662 (bos.rte.date.5.3.0.51)
• AIX 5.2: Technology Level 9 is the minimum level on which to apply the DST fix, IY91985 (bos.rte.date.5.2.0.41). See the note about AIX 5.2 TL09 in the AIX 5L Version 5.2 section above before installing.

NOTE: These databases did not exist for AIX releases prior to 5.2.

NOTE: After installing these APARs, a reboot will not be necessary unless an update to 5.3 TL5 or 5.2 TL9 was also performed.

Java for AIX

If you use Java on AIX, you may want to install the corresponding Java levels with current DST information. APAR numbers are associated with the specific level of Java that is installed. The APARs relating to DST and Java are:

For additional information on the impact of Daylight Saving Time on Java that ships with AIX, see: Changes to Daylight Saving Time will affect IBM Java and AIX.

WebSM

The WebSM system management configuration tool has code to display a default DST value if the TZ variable is not set in /etc/environment. This should rarely if ever be the case, and the WebSM updates do not impact the DST setting of your operating system. However, if you use WebSM and set your TZ variable through this interface, you may want to install the updated WebSM APARS as follows:

• AIX 5.3: Technology Level 5 is the minimum level that includes the DST fix, APAR IY83394 (Fileset: sysmgt.websm.framework 5.3.0.50).
• AIX 5.2: Technology Level 9 is the minimum level that includes the DST fix, APAR IY86260 (Fileset: sysmgt.websm.framework 5.2.0.95). See the note about AIX 5.2 TL09 in the AIX 5L Version 5.2 section above before installing.

NOTE: Installing these new Technology Levels will require a system reboot.

International Components for Unicode (ICU)

The official inclusion of ICU libraries on AIX began in 2006, and includes the new US DST rules. The minimum levels required to have these new rules are:

• AIX 5.3 Technology Level 5, which includes ICU libraries (Filesets: ICU4C.adt 5.3.0.0, ICU4C.rte 5.3.0.0, ICU4C.man.en_US 5.3.0.0)
• AIX 5.2 Technology Level 9, which includes ICU libraries (Filesets: ICU4C.adt 5.2.0.0, ICU4C.rte 5.2.0.0, ICU4C.man.en_US 5.2.0.0). See the note about AIX 5.2 TL09 in the AIX 5L Version 5.2 section above before installing.

These Technology Levels provide ICU Version 3.4 for AIX, packaged in the fileset levels which reflect the appropriate AIX version.

NOTE: Installing these new Technology Levels will require a system reboot.

NOTE: These ICU updates are optional unless you specifically have applications that depend on the ICU libraries. If you do not currently have any ICU4C filesets installed, then the ICU update is not relevant.