Kernel threads allow a multithreaded application to have a thread
    executing on every CPU in a multiprocessor system. The /THREADS_
    ENABLE qualifier allows you to turn kernel threads on and off on
    a per-image basis.

    When you specify this qualifier, the OpenVMS linker sets the
    appropriate bits in the dynamic segment (x86 and I64) or the
    image header (Alpha and VAX) of the image being linked. These
    bits control the following:

    o  Whether the image is allowed to enter a multiple kernel
       threads environment

    o  Whether the image can receive upcalls from the OpenVMS
       scheduler

    If you do not specify this qualifier, the OpenVMS x86 and I64
    linker check whether the image to be linked is threaded. If
    it is, the linker automatically enables upcalls and informs
    the user with a message. This behavior can be overwritten with
    negating the qualifier or enabling only multiple kernel threads.

    Format

      /THREADS_ENABLE[=(MULTIPLE_KERNEL_THREADS,UPCALLS)]

      /NOTHREADS_ENABLE (default)