oracle extend

SELECT 
   a.tablespace_name, 
   a.file_name, 
   a.bytes allocated_bytes, 
   b.free_bytes
FROM 
   dba_data_files a, 
   (SELECT file_id, SUM(bytes) free_bytes
    FROM dba_free_space b GROUP BY file_id) b
WHERE 
   a.file_id=b.file_id
ORDER BY 
   a.tablespace_name;


-- ALTER DATABASE DATAFILE  'C:\ORACLEXE\APP\ORACLE\ORADATA\XE\USERS.DBF' AUTOEXTEND ON;