As a DBA, you must keep an eye on the largest tables in the database. There are many things that get impacted with the largest objects like DB performance, growth, index rebuild etc. The below query gives you the top 10 largest tables in oracle database.
Query to check top 10 largest tables in Oracle
SELECT * FROM (select SEGMENT_NAME, SEGMENT_TYPE, BYTES/1024/1024/1024 GB, TABLESPACE_NAME from dba_segments order by 3 desc ) WHERE ROWNUM <= 10