text: col msg format a50 heading 'Space Details'
  select 'Allocated Space : '||to_char(sum(bytes)/1024/1024/1024,'9,999.99')||' GB' msg
    from dba_data_files
  union all
  select 'Used Space      : '||to_char(sum(bytes)/1024/1024/1024,'9,999.99')||' GB'  msg
    from dba_segments
  /
  prompt 
  exit
  