Library /sys$common/syshlp/DFUHLP.HLB
DFU, DEFRAG, Qualifiers, /LBN=<logical-block-number>
 *Conan The Librarian 

 Move a single file to the target logical block number. This is faster
 than having the file system search for a new LBN location.
 Caution: Use this qualifier only for processing a single file, not
 a list of files. If there is not enough contiguous free space
 available at the target LBN Defrag will fail with a
 DEVICEFULL error.
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