据库文件
select * from dba_data_files;
（6）查询当前存在的表空间
select * from v$tablespace;
（7）表空间分配情况
select tablespace_name,sum(bytes)/1024/1024 from dba_data_files group by tablespace_name;
（8）查询表空间剩余空间
select tablespace_name,sum(bytes)/1024/1024 from dba_free_space group by tablespace_name;