/sys$common/syshlp/helplib.hlb Sys Parameters, VBSS_ENABLE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    (VAX only) This special parameter is used by Compaq and is
    subject to change. Do not change this parameter unless Compaq
    recommends that you do so.

    This parameter enables virtual balance slots (VBS) to be
    created. A virtual balance slot holds the mapping for a memory-
    resident process that does not currently own a real balance slot
    (RBS). The set of real balance slots is timeshared among all
    memory-resident processes. With VBS enabled, the quantity of
    memory-resident processes is limited by the system parameter
    MAXPROCESSCNT. With VBS disabled, the quantity of memory-resident
    processes is limited by the system parameter BALSETCNT.

    When creating a new process, if the set of real balance slots
    is allocated, then a virtual balance slot is created and the
    owner of a real balance slot is selected and transitioned to
    the virtual balance slot. The new process is created in the real
    balance slot. Processes are transitioned (faulted) back to a real
    balance slot as they are scheduled to execute on a CPU.

    Bit    Result

    0      Enables VBS. All other VBS enables are subordinate to this
           enable. The default is disabled.

    1      Enables the creation of a map for process-based
           direct I/O, allowing the process with direct I/O (DIO)
           outstanding to be transitioned to a virtual balance slot.
           Without DIO maps, a process with DIO outstanding retains
           its real balance slot for the duration of the DIO. This
           reduces the pool of available real balance slots for
           timesharing, which may result in a higher rate of faulting
           into the limited set of real balance slots. The default is
           enabled.

    2-7    Reserved to Compaq for future use.

    VBSS_ENABLE is an AUTOGEN parameter.