Samet Kilictas's Blog

The size of a table can be found using oracle’s segment tables. Basically following code block returns a result of table size within related tablespaces in terms of MB and GB:

   SELECT tablespace_name,
          segment_name AS TABLENAME,
          trunc((sum(BYTES) / 1024 / 1024), 2) MB,
          trunc((sum(BYTES) / 1024 / 1024 / 1024), 2) GB
     FROM user_segments
 GROUP BY tablespace_name, segment_name

This way you may access only the tablespaces of logged in user