“Device Activity Detail” reports activity on each logical device. It is useful for checking that I/O is well balanced across the database devices and for finding a device that might be delaying I/O. For example, if the “Task Context Switches Due To” data indicates a heavy amount of device contention, you can use “Device Activity Detail” to figure out which device(s) is causing the problem.
This section prints the following information about I/O for each data device on the server:
The logical and physical device names
The number of reads and writes and the total number of I/Os
The number of device semaphore requests immediately granted on the device and the number of times a process had to wait for a device semaphore