Reverting to previous versions

This section tells you what to do if you want to revert to using a previous version of WebSphere MQ for z/OS for some exceptional reason.

If you choose to revert to a previous version of WebSphere MQ, note that, as a general rule, data such as attributes (or in some cases, objects) relating to the new function in Version 6 will be lost. The more you have used the new functions of Version 6, the less practical it will be to go back to an earlier version.

If you want to revert to an earlier version of WebSphere MQ, contact your IBM(R) support center. The support center will provide you with the 'Coexistence PTF', which you must apply to your system to revert to an earlier version. The information in the PTF includes a description of the data relating to new function that will be lost.

When you have reverted to a previous version, if you have defined a CF structure with CFLEVEL(4), that structure, queues defined to use it, and any messages on those queues are not accessible while running with a version of code earlier than Version 6.0. The queues and messages are retained, but if the Coupling Facility fails and all members of the queue-sharing group have been reverted to a previous level, messages might be lost. When you have reverted to Version 5.3.1, CF structures with a CFLEVEL less than 4, queues, and nonpersistent messages are still available.

WebSphere MQ Version 6.0 allows page sets up to 64GB but earlier versions allowed page sets only up to 4GB. If your page set 0 is larger than 4GB it is not possible to fall back to a previous release and restart the queue manager. If other page sets are found to be larger than 4GB when a queue manager restarts in an earlier MQ release, they will be taken off line and messages on them will not be available.

If you migrate from MQSeries(R) Version 5.2 or earlier, you must consider carefully whether you will need the ability to revert to that release. You cannot revert to that release if you migrate directly to Version 6.0. If you think you will need to revert, you must migrate to Version 5.3.1 first and then migrate from Version 5.3.1 to Version 6.0. This allows you to revert first to Version 5.3.1 and then to your previous release.