Unit-of-recovery log records

Most of the log records describe changes to WebSphere MQ queues. All such changes are made within units of recovery.

WebSphere MQ uses special logging techniques involving undo/redo and compensating log records to reduce restart times and improve system availability.

One effect of this is that the restart time is bounded. If a failure occurs during a restart so that the queue manager has to be restarted a second time, all the recovery activity that completed to the point of failure in the first restart does not need to be reapplied during a second restart. This means that successive restarts do not take progressively longer times to complete.