VMS Help DUMP, Qualifiers, /BLOCKS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BLOCKS[=(option[,...])]

    Dumps the specified blocks one block at a time, which is the
    default method for all devices except network devices.

    Block numbers are specified as integers relative to the beginning
    of the file. Typically, blocks are numbered beginning with 1.
    If a disk device is mounted using the /FOREIGN qualifier, blocks
    are numbered beginning with zero. Select a range of blocks to be
    dumped by specifying one of the following options:

    START:n    Specifies the number of the first block to be dumped;
               the default is the first block.

    END:n      Specifies the number of the last block to be dumped;
               the default is the last block or the end-of-file (EOF)
               block, depending on whether you have specified the
               /ALLOCATED qualifier.

    COUNT:n    Specifies the number of blocks to be dumped. The COUNT
               option provides an alternative to the END option; you
               cannot specify both.

    If you specify only one option, you can omit the parentheses.

    The /BLOCKS and /RECORDS qualifiers are mutually exclusive.

    Use the /BLOCKS qualifier to dump random blocks from Files-11
    volumes. This procedure requires LOG-IO (logical I/O) privilege.