The kernel's daemon and housekeeping processes are assigned to the system scheduler class. Users can neither add processes to nor remove processes from this class, nor can they change the priorities of these processes. The command ps -cel lists the scheduler class of all processes. Processes in the system class are identified by a SYS entry in the CLS column.
The nice(1) command and the nice(2) function work as in previous versions of the UNIX system. They let you change the priority of a time-sharing process. Use lower numeric values to assign higher time-sharing priorities with these functions.
To change the scheduler class of a process or to specify a real-time priority, you must use one of the priocntl functions. Use higher numeric values to assign higher priorities with the priocntl(2) functions.