查看表空间

select /*+ ordered use_hash(a,b,c) */

 a.file_id as "文件id",

 a.file_name as "文件名",

 a.tablespace_name as "表空间名",

 a.filesize as "文件大小",

 b.freesize as "剩余空间",

 (a.filesize - b.freesize)  as "已用空间",

 c.hwmsize as "高水位大小"

  from (select tablespace_name,file_id, file_name, round(bytes / 1024 / 1024) filesize

          from dba_data_files) a,

       (select file_id, round(sum(dfs.bytes) / 1024 / 1024) freesize

          from dba_free_space dfs

         group by file_id) b,

       (select file_id, round(max(block_id) * 8 / 1024) HWMsize

          from dba_extents

         group by file_id) c

 where a.file_id = b.file_id

   and a.file_id = c.file_id

 order by b.freesize desc

sys用户执行，在pl/sql下