Reverting a queue manager to a previous version

You can remove an upgrade before you have started a queue manager. After a queue manager has been started, if you remove the upgrade, the queue manager will not work.

You must back up your system before starting migration. You can either back up queue manager data, or use a backup queue manager; see Backing up and restoring IBM® MQ. To back up, you must stop the queue manager.

You can reduce the downtime and risk caused by queue manager migration, by verifying the new version first, using a different queue manager. Unless the platform supports queue manager coexistence, you need to perform the verification on a different server, or in a virtualized environment on the same server. If the platform you are upgrading supports queue manager coexistence, you can install the new version of IBM MQ on the same server, verify it, and minimize downtime to the time required to stop, backup, and restart the queue manager.

On z/OS®, before Version 7.0.1, it is possible to revert to a previous level, as long as you have applied the correct PTFs.

On z/OS, from Version 7.0.1 onwards, it is impossible to revert to an earlier release after running with OPMODE NEWFUNC. Otherwise, you can backward migrate, as described in Migration PTFs.

On z/OS, you must migrate queue managers manually between compatibility mode and new function mode by setting the OPMODE parameter. If you have never switched a queue manager to new function mode, you can still run it against the earliest release it is compatible with. You must have applied compatibility PTFs to the earlier release before starting a queue manager at the new command level. The compatibility level is shown in the log.