/REPLACE=RETAIN

    Retains, when an RT-11 volume is initialized, the bad block
    replacement table and any existing FILE.BAD files.

    The RETAIN option is required; EXCHANGE cannot build a
    replacement table for a volume. The RT-11 system builds and
    uses the table based on specific hardware error conditions. The
    OpenVMS I/O system is different, and cannot be relied upon to
    generate exactly the same error conditions. Therefore, it is not
    possible for EXCHANGE to generate the same replacement table that
    would be generated by RT-11.

    If no replacement table is present, the qualifier /REPLACE=RETAIN
    is equivalent to /BADBLOCKS=RETAIN.