Autumn time" /> Autumn (fall) time change

 

Autumn (fall) time change

When clocks go backward in the autumn (fall), we cannot restart the queue manager immediately after changing the clock backwards. If you do so, there is a risk that WebSphere MQ will write duplicate timestamps to the journal. You should ensure that WebSphere MQ is stopped for an hour either before or after the time change and UTC offset update, to avoid the problems associated with setting the system clock backward by an hour. You are not recommended to use the Time Zone system value when WebSphere MQ for iSeries is actively being used on an i5/OS system.

In environments where downtime must be minimized, an enforced outage of one hour might not be acceptable. IBM is looking into providing a better solution, but until this is available, the only alternative to quiescing the queue manager for an hour is to perform a controlled cold start of the system. A controlled cold start is where all queues are emptied of any persistent messages and the queue manager is cleanly shut down. The queue manager journal data can then be deleted using the cold start procedure. This eliminates the risk of losing messages, but it deletes all media recovery information. You will not be able to recover damaged objects without media recovery information, so you should ensure that you have backed up your object definitions before attempting this. Your IBM service representative will be able provide details of this procedure.