Top index sizes of table/schema - oracle database script

--- Find index name and their sizes of a table  SELECT idx.table_name,bytes/1024/1024/1024 FROM dba_segments seg, dba_indexes idx where idx.table_name='&TABLE_NAME' AND idx.index_name = seg.segment_name GROUP BY idx.table_name order by 1;  -- Find total_index_size of respective tables in a schema  SELECT idx.table_name, SUM(bytes/1024/1024/1024) FROM dba_segments seg, dba_indexes idx WHERE idx.table_owner = 'SIEBEL' AND idx.owner = seg.owner AND idx.index_name = seg.segment_name GROUP BY idx.table_name order by 1