Generate a diskblock usage report. DFU will report per
    UIC/Identifier the blocks used/allocated, and the number of
    file headers used. If diskquota is enabled a third column will
    be added to the report with the blocks used according to QUOTA.SYS.
    If an UIC or Identifier is entered then only that UIC will
    be reported.
    The diskquota used must satisfy the rule :

    QUOTA used = blocks allocated + # of file headers.