Re: MQ AS400 time change

I just got off the phone with IBM and they confirm what Dave has written below (thanks Dave).

If you are on WebSphere MQ 6.0.2.3 or higher you have the change and do not need to quiece MQ.

To verify what version of WebSphere MQ you are on use this command:

dspmqmver

Happy time zone change everyone.

Jerry

On 11/4/2010 10:51 AM, Dave Snyder wrote:

Here is the info I have:

Daylight Saving Time
All WebSphere MQ users who reside in time zones affected by DST have
encountered the limitation of handling that change for WebSphere MQ on IBM
i. It was necessary for WebSphere MQ to be quiescent during DST change.
This led to problem behavior in WebSphere MQ 6.0.2.2 and earlier versions.
Let me explain.
When clocks go backward one hour in the fall, users had to stop the queue
manager for an hour either before or after the time change because time
stamps based on system clock was used as a unique identifier to record data
in journals. If WebSphere MQ remained active during the DST change, there
was a risk of duplicate entries in the journal.
When clocks go forward one hour in the spring, users werenât required to
stop the queue manager and the QMQM subsystem for the time it took to
adjust the clock. However, IBM advised doing so as a precaution in case the
time was adjusted incorrectly and required the clocks to go backward.
Nevertheless, the subsystem and the queue manager could be restarted
immediately after changing the system clock.
Besides the inconvenience, this unpleasant behavior had significant
implications in certain industries like banking where stopping WebSphere MQ
for an hour isnât acceptable. In fact, this factor prohibited many
customers from using WebSphere MQ on IBM i.
For V5R3 and later versions of IBM i, an automatic method is available to
adjust the clock using the Time Zone (QTIMZON) system value. However, with
WebSphere MQ installed, this feature wouldâve complicated the time change
because automatic time change wouldnât provide a chance to stop WebSphere
MQ queue managers before changing the system clock and hence the journals
would have duplicate timestamps. To avoid this, manual time change was
still recommended.
IBM recognized this issue and responded with a change. Starting with
WebSphere MQ 6.0.2.3, WebSphere MQ is no longer required to be quiescent
during DST changes.
WebSphere MQ developers created an algorithm thatâs independent of the
timestamp. The algorithm uses existing WebSphere MQ elements internally to
eliminate time-change impacts. This new feature in the more current
versions of WebSphere MQ on IBM i has been embraced by our customers
because itâs no longer necessary to pay attention to DST changes and plan
for manual intervention.
This means WebSphere MQ can run during DST change, users can exploit the
automatic time change behavior of the system by setting the QTIMZON system
value and no manual intervention is required.



Dave Snyder
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From: Neeraj J<neerajj001@xxxxxxxxx>
To: Midrange Systems Technical Discussion<midrange-l@xxxxxxxxxxxx>
Date: 11/04/2010 09:53 AM
Subject: MQ AS400 time change
Sent by: midrange-l-bounces@xxxxxxxxxxxx



Do we have to shut MQ when the time changes in coming week as entries are
based on time stamps ?
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