-- 登录
sqlplus / as sysdba

-- 查看当前连接数
select count(*) from v$process;

-- 查看允许最大连接数 (默认为 150)
select value from v$parameter where name = 'processes';

-- 修改最大连接数
alter system set processes = 500 scope = spfile;

-- 查看当前有哪些用户正在使用数据
SELECT osuser, a.username,cpu_time/executions/1000000||'s', sql_fulltext,machine 
from v$session a, v$sqlarea b
where a.sql_address = b.address order by cpu_time/executions desc;