VMS Help Sys Parameters, DUMPSTYLE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    DUMPSTYLE specifies the method of writing system dumps.

    DUMPSTYLE is a 32-bit mask, with the following bits defined.
    Each bit can be set independently. The value of the system
    parameter is the sum of the values of the bits that have been
    set. Remaining or undefined values are reserved for Compaq use
    only.

    Bit              Mask       Description

    0                00000001   0 =  Full dump (SYSGEN default).
                                     The entire contents of physical
                                     memory are written to the dump
                                     file.
                                1 =  Selective dump. The contents of
                                     memory are written to the dump
                                     file selectively to maximize
                                     the usefulness of the dump file
                                     while conserving disk space.

    1                00000002   0 =  Minimal console output.
                                1 =  Full console output (includes
                                     stack dump, register contents,
                                     and so on).
    2                00000004   0 =  Dump to system disk.

                                1 =  Dump off system disk (DOSD) to
                                     an alternate disk. (Refer to the
                                     OpenVMS System Manager's Manual
                                     for details.)

    3 (Alpha only)   00000008   0 =  Do not compress.
                                1 =  Compress. (See note below.)

    4 - 14                           Reserved for Compaq use only.

    15 (VAX only)    00008000   0 =  Disable use of bits 16 - 27.
                                1 =  Enable use of bits 16 - 27.

    16 - 27 (VAX     0FFF0000        Range of DOSD unit numbers.
    only)

    28 - 31                          Reserved for Compaq use only.

    Note that VAX systems do not support dump compression. Also,
    VAX-only bits are specific to VAX 7000s.

    If you plan to enable the Volume Shadowing minimerge feature on
    an Alpha system disk, be sure to specify DOSD to an alternate
    disk.

                                   NOTE

       On Alpha systems, you can save space on the system disk
       and, in the event of a crash, save time recording the system
       memory, by using the OpenVMS Alpha dump compression feature.
       Unless you override the default AUTOGEN calculations (by
       setting DUMPSTYLE in MODPARAMS.DAT), AUTOGEN uses the
       following algorithm:

       o  On a system with less than 128 MB of memory, the system
          sets the DUMPSTYLE to 1 (a raw selective dump) and sizes
          the dump file appropriately.

       o  On a system with 128 MB of memory or greater, the system
          sets the DUMPSTYLE to 9 (a compressed selective dump),
          and creates the dump file at two-thirds the value of the
          corresponding raw dump.

    Examples:

    The mask of 00000006 directs the system to send a full dump, with
    full console output, off the system disk (to the alternate disk).

    For a VAX 7000, a mask of 00098006 directs the system to send a
    full dump with full console output to the DOSD whose unit number
    is 9.

    On Alpha systems, the mask of 00000009 directs the system to
    compress a selective dump with minimal console output.

    DUMPSTYLE has AUTOGEN and DYNAMIC attributes.