SQL> SELECT  TEXT_VC
  2    FROM  DBA_VIEWS
  3    WHERE VIEW_NAME = 'DBA_EXTERNAL_TABLES'
  4  /

TEXT_VC
--------------------------------------------------------------------------------
select u.name, o.name, 'SYS', xt.type$, 'SYS', xt.default_dir,
       decode(xt.reject_limit, 2147483647, 'UNLIMITED', xt.reject_limit),
       decode(xt.par_type, 1, 'BLOB', 2, 'CLOB',       'UNKNOWN'), -- ответ на вопрос # 3
       case when xt.par_type = 2 then xt.param_clob else NULL end,
       decode(bitand(xt.property, 3), 2, 'REFERENCED', 1, 'ALL',     'UNKNOWN')
from sys.external_tab$ xt, sys.obj$ o, sys.user$ u
where o.owner# = u.user#
  and o.subname IS NULL
  and o.obj# = xt.obj#


SQL>