oracle当前的连接数

怎样查看oracle当前的连接数呢？只需要用下面的SQL语句查询一下就可以了。
select * from v$session where username is not null

select username,count(username) from v$session where username is not null group by username #查看不同用户的连接数

select count(*) from v$session?? #连接数

Select count(*) from v$session where status='ACTIVE'　#并发连接数

show parameter processes?? #最大连接

alter system set processes = value scope = spfile;重启数据库?? #修改连接

/home/oracle9i/app/oracle9i/dbs/init.ora

/home/oracle9i/app/oracle9i/dbs/spfilexxx.ora ## open_cursor