How to Check Schema Size in Oracle Database

Below is the DBA script to check the size of database schema in oracle database:

SQL >    set linesize 150
         set pagesize 5000
         col owner for a15
         col segment_name for a30
         col segment_type for a20
         col TABLESPACE_NAME for a30
     select OWNER,sum(bytes)/1024/1024/1024 "SIZE_IN_GB" from dba_segments group by owner order by owner;