Indexes Not Used

SELECT *
  FROM all_views
 WHERE view_name LIKE '%USAGE%'
select a.index_name, (s.bytes/1024/1024/1024) from all_object_usage a, dba_segments s
where a.index_name=s.segment_name
and a.used='NO'
group by a.index_name;

SELECT SUM (ROUND (bytes / 1024 / 1024 / 1024)) AS GB
  FROM dba_segments
 WHERE segment_name IN (SELECT index_name
                          FROM all_object_usage
                         WHERE used = 'NO');

SELECT * FROM gisdba.dba_object_usage;

SELECT (bytes / 1024 / 1024 / 1024)
  FROM dba_segments
 WHERE segment_name = 'IX_BIL_REFRUN';