Introducing coexistence support for WebSphere MQ on Windows, UNIX, and Linux
Marcela Adan 100000THF9 firstname.lastname@example.org | | Tags:  middleware integration mq messaging websphere
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By Jamie Squibb
WebSphere MQ Software Engineer
IBM Hursley Laboratory
As a member of the WebSphere MQ development organization I hear about requests to enhance the product to satisfy new requirements. These requests vary from the addition of a new property, or attribute, to much larger functional enhancements. WebSphere MQ is usually part of a larger software solution. The inability of WebSphere MQ versions to coexist on Windows, UNIX, and Linux caused problems for customers when migrating from one version to another. This was especially pertinent if using a lot of applications on the same machine, or software products that only certify support for specific versions of WebSphere MQ. Arranging for many applications to have a concurrent outage can be difficult, and can also be disruptive to service level agreements.
This restriction has been lifted as of version 7.1. It is now possible to customize the location where WebSphere MQ is installed, and also to install multiple copies on the same machine, at the same, or different, version. Queue managers can be individually migrated and applications can connect to a queue manager irrespective of which installation it is associated with. This enhancement increases the options available to administrators and can reduce the downtime for a queue manager, during a migration, to the time it takes to stop and then restart it.
So when should you use multiple installations?
If you only have a single queue manager or application, or the impact of an outage during a migration is small, you might favour the simplicity of a single installation. If you have a complex setup, you need to minimise the duration of outages, you’d like to stage the migration of your queue managers and applications, or you wish to maximise flexibility, using multiple installations is something you should consider.
In a multiple installation environment there are additional considerations for administration and application connectivity. However, additional commands and other features have been added to simplify this as much as possible. These include being able to view the available installations, and see, or change, the installation each queue manager is associated with. Support has also been added so applications can load the required WebSphere MQ libraries automatically. This can help isolate applications from installation changes and allows concurrent connections to queue managers associated with different installations. There are a few restrictions, so although many applications will work without change, others may need to be updated before you can use them in such an environment. These considerations are discussed as part of this new capability in the new IBM Redbooks publication IBM WebSphere MQ V7.1 and V7.5 Features and Enhancements.
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