func

    OpenVMS usage:function_code
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value
    Function code specifying the action $SCHED is to perform. The
    func argument is a longword containing this code.

    For a list of the valid function codes for $SCHED, see the HP
    OpenVMS System Services Reference Manual.

 p1, p2, p3

    OpenVMS usage:longword
    type:         longword (unsigned)
    access:       varies
    mechanism:    varies
    The meaning of the p1, p2, and p3 arguments depends on the
    function code specified in the func argument, and is defined
    in the Function Codes section.