今天下午突然大家的数据库都连不上了，起初以为是断线了，后拉经过从起监听、数据库、甚至服务器，都没有解决。而且，在本地和异地使用as sysdba就可以登录，所以认为不是数据和监听的问题。

在客户端连接时报出：

sp2-1503

sp2-0152

两个错误，所以刚开始都是围绕这两个问题查找原因。网上所提供的解决方案都没能解决。

最后还是要通过查看日志，

发现resource_manager_plan 被改成'INTERNAL_QUIESCE'了，将其置空后，数据库即可连接。

ALTER SYSTEM SET resource_manager_plan= '' SCOPE=BOTH;

INTERNAL_QUIESCE:
INTERNAL_QUIESCE -

freezes all sessions out (by setting max number of sessions to 0) except for SYS_GROUP

冻结所有会话除了sys_group组的用户。

RESOURCE_MANAGER_PLAN

specifies the top-level resource plan to use for an instance. The resource manager will load this top-level plan along with all its descendants (subplans, directives, and consumer groups). If you do not specify this parameter, the resource manager is off by default.

You can change the setting of this parameter using the ALTER SYSTEM statement to turn on the resource manager (if it was previously off) or to turn off the resource manager or change the current plan (if it was previously on). If you specify a plan that does not exist in the data dictionary, Oracle returns an error message.