Compression=LZSS
    Compression=Huffman
    Compression=ZLIB=level
    Nocompression

    Allows you to specify the compression method to use before
    writing data to the backup file. This reduces performance, but
    may be justified when the backup file is a disk file, or is being
    backed up over a busy network, or is being backed up to a tape
    drive that does not do its own compression. You probably do not
    want to specify the Compression qualifier when you are backing up
    a database to a tape drive that does its own compression; in some
    cases doing so can actually result in a larger file.

    If you specify the Compression qualifier without a value, the
    default is COMPRESSION=ZLIB=6.

    The level value (ZLIB=level) is an integer between 1 and 9
    specifying the relative compression level with one being the
    least amount of compression and nine being the greatest amount
    of compression. Higher levels of the compression use increased
    CPU time while generally providing better compression. The
    default compression level of 6 is a balance between compression
    effectiveness and CPU consumption.

          OLDER ORACLE RDB 7.2 RELEASES AND COMPRESSED RBF FILES

       Prior releases of Oracle Rdb are unable to read RBF files
       compressed with the ZLIB algorithm. In order to read
       compressed backups with Oracle Rdb 7.2 Releases prior
       to V7.2.1, they must be made with /COMPRESSION=LZSS or
       /COMPRESSION=HUFFMAN explicitly specified (because the
       default compression algorithm has been changed from LZSS to
       ZLIB). Oracle Rdb Version 7.2.1 is able to read compressed
       backups using the LZSS or HUFFMAN algorithms made with prior
       releases.