JAVA J2EE 4 U

 SELECT ROUND(SUM(bytes) / 1024 / 1024 / 1024, 2) AS size_gb

FROM dba_data_files;

SELECT ROUND(SUM(bytes) / 1024 / 1024 / 1024, 2) AS total_size_gb

FROM (

    SELECT bytes FROM dba_data_files

    UNION ALL

    SELECT bytes FROM dba_temp_files

);

SELECT con_id,

       (SELECT name FROM v$containers WHERE con_id = f.con_id) AS pdb_name,

       ROUND(SUM(f.bytes) / 1024 / 1024 / 1024, 2) AS size_gb

FROM cdb_data_files f

GROUP BY con_id;

SELECT ROUND(SUM(bytes)/1024/1024/1024, 2) AS size_gb

FROM dba_data_files

WHERE tablespace_name IN (

    SELECT tablespace_name

    FROM dba_tablespaces

    WHERE con_id = (SELECT con_id FROM v$containers WHERE name = 'PDB_NAME')

);