oracle 查看数据库连接

select count(*) from v$session where username is not null order by machine;  
select * from v$session where username is not null order by machine;  
select count(*) from v$session where username is not null and machine='test1' order by machine ;  
select count(*) from v$session where username is not null and machine='localhost.localdomain' order by machine ;  
select * from v$process where username is not null ;  
select * from V$SHARED_SERVER_MONITOR ;  
SELECT * FROM v$open_cursor;  
SELECT sql_text,COUNT(*) FROM v$sql s , v$session se WHERE se.prev_hash_value =s.hash_value GROUP BY sql_text;