oracle当前连接数，会话数


　1.查看session：

　　select * from v$session where username is not null

　　select username,count(username) from v$session where username is not null group by username

　2.当前连接数：

select count(*) from v$process

　3.查看连接数参数的设置情况

　　select value from v$parameter where name = 'processes'

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