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)

1  –  Qualifier Values

 MULTIPLE_KERNEL_THREADS

    On x86, I64 and Alpha systems, this keyword sets the
    MULTIPLE_KERNEL_THREADS bit in the dynamic segment (x86 and
    I64) or the image header (Alpha) of the image being built. This
    bit indicates to the image activator that the image can be run
    in a multiple kernel threads environment.

    If you specify this keyword for OpenVMS VAX links, it is ignored.

 UPCALLS

    This qualifier sets the UPCALLS bit in the OpenVMS dynamic segment
    (x86 and I64) or image header (Alpha and VAX) of the image being
    built. This bit indicates to the image activator that the process
    can receive upcalls from the OpenVMS scheduler.

    When the /THREADS_ENABLE qualifier is specified without either
    the MULTIPLE_KERNEL_THREADS or UPCALLS keyword, the linker sets
    both bits by default.