/ZLIB_LEVEL=n

    The /ZLIB_LEVEL qualifier provides a tuning mechanism for the
    amount of compression performed and resulting CPU time required
    when creating a compressed save set using /DATA_FORMAT=COMPRESS.

    The compression value n is required syntax and may range from 1 to 9.

    A value of 1 provides only the initial level of compression, using the
    least amount of CPU possible.  This value corresponds to the need
    to finish backups in the smallest time possible but still compressing
    the data to some degree.  Even with this smallest value, the data
    compression can be very dramatic.

    A value of 9 provides the highest level of compression, but requires
    more CPU time to accomplish.  This value corresponds to the need
    to produce the smallest backup save sets possible, for example to
    fit on a fixed size output media which is near capacity.

    If /ZLIB_LEVEL is not specified, BACKUP uses the default compression
    value which is equivalent to level 6.

    /ZLIB_LEVEL is only valid in conjunction with /DATA_FORMAT=COMPRESS.
    It is only used for save set creation.  The qualifier is ignored for
    restore operations.