表空间回收操作判断

SELECT a.tablespace_name "表空间",
    a.bytes / 1024 / 1024 "表空间大小(M)",
    (a.bytes - b.bytes) / 1024 / 1024 "已使用空间(M)",
    b.bytes / 1024 / 1024 "空闲空间(M)",
    round(((a.bytes - b.bytes) / a.bytes) * 100, 2) "使用比"
FROM   (SELECT tablespace_name,
      SUM(bytes) bytes
  FROM   dba_data_files
  GROUP  BY tablespace_name) a,
    (SELECT tablespace_name,
      SUM(bytes) bytes,
      MAX(bytes) largest
  FROM   dba_free_space
  GROUP  BY tablespace_name) b
WHERE  a.tablespace_name = b.tablespace_name
ORDER  BY ((a.bytes - b.bytes) / a.bytes) DESE;