There is no correspondence between your operating system’s reports on CPU usage and the Adaptive Server internal “CPU busy” information.
A multithreaded database engine in process mode is not allowed to block on I/O. While asynchronous disk I/O is being performed, Adaptive Server services other user tasks that are waiting to be processed. If there are no tasks to perform, Adaptive Server enters a busy-wait loop, waiting for completion of the asynchronous disk I/O. This low-priority busy-wait loop can result in high CPU usage, but because of its low priority, it is generally harmless.
Adaptive Serves in threaded mode can block on I/O.
In process mode, it is normal for an Adaptive Server
to exhibit high CPU usage while performing an I/O-bound
task.
