--查看表空间大小
SELECT t.tablespace_name, round(SUM(bytes / (1024 * 1024)), 0) ts_size --类型M
FROM dba_tablespaces t, dba_data_files d 
WHERE t.tablespace_name = d.tablespace_name 
GROUP BY t.tablespace_name; 

--字符集
select userenv('language') from dual; 
select * from v$nls_parameters; 
select * from nls_database_parameters
 
--最大连接数
select value from v$parameter where name = 'processes'

--当前连接数
select count(*) from v$session;