/sys$common/syshlp/helplib.hlb Sys Parameters, SCSI_NOAUTO  *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.

    SCSI_NOAUTO prevents the loading of a disk or tape SCSI class
    driver for any given device ID in a configuration that includes a
    SCSI third-party device. The SCSI_NOAUTO system parameter stores
    a bit mask of 32 bits, where the low-order byte corresponds to
    the first SCSI bus (PKA0), the second byte corresponds to the
    second SCSI bus (PKB0), and so on, as follows:

    #31   24 23   16 15    8 7     0
    +-------+-------+-------+-------+
    |   D   |   C   |   B   |   A   |
    +-------+-------+-------+-------+

    For each SCSI bus, setting the low-order bit inhibits automatic
    configuration of the device with SCSI device ID 0; setting the
    second low-order bit inhibits automatic configuration of the
    device with SCSI device ID 1, and so forth. For instance, the
    value 00002000 subscript 16 prevents the device with SCSI ID 5
    on the bus identified by SCSI port ID B from being configured.
    By default, all the bits in the mask are cleared, allowing all
    devices to be configured.

    SCSI_NOAUTO is a DYNAMIC parameter.