关于ORACLE RESTRICT模式，以及START OPEN RECOVER 


说明如下：
Restricting Access to an Instance at Startup
You can start an instance, and optionally mount and open a database, in restricted 
mode so that the instance is available onlyto administrative personnel (not general 
database users). Use this mode of instance startup when you must accomplish one of 
the following tasks:
■ Perform an export or import of data
■ Perform a data load (with SQL*Loader)
■ Temporarily prevent typical users from using data
■ Perform certain migration or upgrade operations
Typically, all users with the CREATE SESSIONsystem privilege can connect to an open 
database. Opening a database in restricted mode allows database access only to users 
with both the CREATE SESSIONand RESTRICTED SESSIONsystem privilege. Only 
database administrators should have the RESTRICTED SESSIONsystem privilege. 


关于如上文档，说明受限模式可以再你想做一些维护的时候，而不想其他非restrict权限用户登录的时候使用。
可以和STARTUP进行搭配启动实例
startup [nomount|mount|open} restrict;
而ORACLE RESTART也可以使用
srvctl start database -d db_unique_name-o restrict


同时在正常数据库使用期间也可以使用
SQL> ALTER SYSTEM DISABLE RESTRICTED SESSION;
 
System altered
 
SQL> ALTER SYSTEM enable RESTRICTED SESSION;
 
System altered


来启用和禁用。但是注意经过测试，这个操作知识影响随后的会话。已经连接的会话不受影响




关于open recover 说明如下：
If you know that media recovery is required, you can start an instance, mount a 
database to the instance, and have the recovery process automatically start by using 
one of these commands:
也就是说如果你确定需要进行介质恢复的时候可以使用，而代替RECOVER DATABASE。但是用处不大
恢复是一件严肃的事情，一般不会交由自动处理。


使用如下命令启动：
STARTUP OPEN RECOVER 
而ORACLE RESTART也可以使用
srvctl start database -d db_unique_name-o "open,recover"