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 (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

    Format

      /THREADS_ENABLE[=(MULTIPLE_KERNEL_THREADS,UPCALLS)]

      /NOTHREADS_ENABLE (default)