In the shutdown stats there are CPU and Wait Time. Does the wait time here indicate time waiting for I/O processing? Is there anything else it could be waiting for?
The Waittime in the stats (mainframe) does indicate the time the nucleus was in it´s general wait processing. This means this is the time the nucleus did not ´proceesed´ any CPUtime.
Due to the multithreading this means (in most cases) that either every active thread was waiting for an I/O or that there was no other work to do and the nucleus is waiting for new commands coming in.
That means that this waittime it not directly showing the time waiting for I/O processing, because if there are other threads which can be processed (i.e. RC command without I/O) only one thread is waiting for I/O but the nucleus in general does not go into the general wait state.
To get a better feeling about the workload of the nucleus look at the Distribution of commands by thread , the high water mark of the command queue and during runtime with AOS to the command queue and threadtable.