GV$FLASHBACK_DATABASE_STAT definition in Oracle Database 11.2
GV$FLASHBACK_DATABASE_STAT

select
  inst_id,                                 -- INST_ID NUMBER
  to_date(                                 -- BEGIN_TIME DATE
    btime, 'MM/DD/RR HH24:MI:SS','NLS_CALENDAR=Gregorian'),
  to_date(                                 -- END_TIME DATE
    etime, 'MM/DD/RR HH24:MI:SS','NLS_CALENDAR=Gregorian'),
  fbw*512,                                 -- FLASHBACK_DATA NUMBER
  dbw*512,                                 -- DB_DATA NUMBER
  redow*512,                               -- REDO_DATA NUMBER
  to_number(fbsz)                          -- ESTIMATED_FLASHBACK_SIZE NUMBER
from
  x$krfgstat

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