inactive sessiono

http://blog.youkuaiyun.com/aaaaaaaa2000/article/details/7392431
在这个里面看到885的进程阻塞了很多其他进程，但是885进程的状态竟然是inactive session的，那这个inactive session 到底是干啥的？这个状态什么含义？



http://blog.youkuaiyun.com/tianlesoftware/article/details/6539297--这个文件里有对inactive

“

当设置了resource_limit=true 。通过idle_time限制session idle 时间。session idle超过设置时间，状态为sniped (v$session).,然而OS下的process并不会释放，当session(user process) 再次与server process 通讯，将关闭相应的server process.

sqlnet.expire_time 的原理不一样，Oracle Server 发送包探测dead connection ，如果连接关闭，或者不再用，则关闭相应的server process.

以上两者组合使用，减少server process,防止process超过init$ORACLE_SID极限值。

”

有关状态的说明：

（1）active 处于此状态的会话，表示正在执行，处于活动状态。

            官方文档说明：

            Any session that is connected to the database and is waiting for an event that does not belong to the Idle wait class is considered as an active session.

 

（2）killed处于此状态的会话，被标注为删除，表示出现了错误，正在回滚。

            当然，也是占用系统资源的。还有一点就是，killed的状态一般会持续较长时间，而且用windows下的工具pl/sql developer来kill掉，是不管用的，要用命令：alter system kill session 'sid,serial#' ;

 

（3）inactive 处于此状态的会话表示不是正在执行的

            该状态处于等待操作(即等待需要执行的SQL语句)，通常当DML语句已经完成。 但连接没有释放，这个可能是程序中没有释放，如果是使用中间件来连接的话，也可能是中间件的配置或者是bug 导致。

 

            inactive对数据库本身没有什么影响，但是如果程序没有及时commit，那么就会造成占用过多会话。容易是DB 的session 达到极限值。

二. 处理inactive 状态的session

            在前面说不处理inactive 状态的session，但是还是有方法来解决的。 有两种方法。

 

2.1 在 sqlnet.ora文件中设置expire_time 参数

官网有关这个参数的说明：

http://download.oracle.com/docs/cd/B19306_01/network.102/b14213/sqlnet.htm

 

SQLNET.EXPIRE_TIME

Purpose

            Use parameter SQLNET.EXPIRE_TIME to specify a the time interval, in minutes, to send a probe to verify that client/server connections are active. Setting a value greater than 0 ensures that connections are not left open indefinitely, due to an abnormal client termination. If the probe finds a terminated connection, or a connection that is no longer in use, it returns an error, causing the server process to exit. This parameter is primarily intended for the database server, which typically handles multiple connections at any one time.

            sqlnet.expire_time 的原理：Oracle Server 发送包探测dead connection ，如果连接关闭，或者不再用，则关闭相应的server process.

 

Limitations on using this terminated connection detection feature are:

（1）It is not allowed on bequeathed connections.-----对 bequeathed connections说明

Simply an Oracle client-server connection that uses IPC (Inter Process Communication) and not TCP (network connection established via the Listener).
In other words, the client and server process communicates directly (via IPC) with one another. There's no network layer in between that serves as the communication layer.
Obviously, this also means that both client process and server process run on the same kernel - as IPC is a communication method that the kernel provides for processes it is executing, to communicate with one another.
（是否可以理解为client与server是在同一机器上）

（2）Though very small, a probe packet generates additional traffic that may downgrade network performance.---会占用网络带宽

（3）Depending on which operating system is in use, the server may need to perform additional processing to distinguish the connection probing event from other events that occur. This can also result in degraded network performance.

 

Default ：0

Minimum Value ：0

Recommended Value ：10

 

Example

SQLNET.EXPIRE_TIME=10----（分钟）
修改完之后需要reload监听

 

 

2.2 设置用户profile的idle_time 参数

           

之前整理的一篇有关profile的文章：

            Oracle 用户 profile 属性

            http://blog.youkuaiyun.com/tianlesoftware/archive/2011/03/10/6238279.aspx

 

            注意，要启用idle_time 要先启用RESOURCE_LIMIT参数。 该参数默认是False。 官网说明如下：

 

RESOURCE_LIMIT

Property	Description
Parameter type	Boolean
Default value	false
Modifiable	ALTER SYSTEM
Range of values	true | false

 

            RESOURCE_LIMIT determines whether resource limits are enforced in database profiles.

 

Values:

            TRUE： Enables the enforcement of resource limits

            FALSE：Disables the enforcement of resource limits

 

如下blog 在这块说的比较清楚，并提供了相关的脚本：

            sqlnet.expire_time and IDLE_TIME

            http://space.itpub.net/10687595/viewspace-420407

 

 

            IDLE_TIME Specify the permitted periods of continuous inactive time during a session, expressed in minutes. Long-running queries and other operations are not subject to this limit.

 

            A valid database connection that is idle will respond to the probe packet causing no action on the part of the Server , whereas the resource_limit will snipe the session when idle_time is exceeded. The 'sniped' session will get disconnected when the user(or the user process) tries to communicate with the server again.

           

            -- 通过idle_time限制session idle 时间。session idle超过设置时间，状态为sniped (v$session).,然而OS下的process并不会释放，当session(user process) 再次与server process 通讯，将关闭相应的server process.

 

What does 'SNIPED' status in v$session mean?

            When IDLE_TIME is set in the users' profiles or the default profile. This will kill the sessions in the database (status in v$session now becomes SNIPED) and they will eventually disconnect. It does not always clean up the Unix session (LOCAL=NO sessions).

            At this time all oracle resources are released but the shadow processes remains and OS resources are not released. This shadow process is still counted towards the parameters of init.ora.

            This process is killed and entry from v$session is released only when user again tries to do something. Another way of forcing disconnect (if your users come in via SQL*Net) is to put the file sqlnet.ora on every client machine and include the parameter "SQLNET.EXPIRE_TIME" in it to force the close of the SQL*Net session

sqlnet.expire_time

            sqlnet.expire_time actually works on a different principle and is used to detect dead connections as opposed to disconnecting(actually 'sniping') a session based on idle_time which the profile accomplishes.

            But again, as you mentioned, expire_time works globally while idle_time profile works for that user. You can use both of them to make sure that the client not only gets sniped but also gets disconnected if the user process abnormally terminates.

 

修改示例：

SQL>alter profile default limit idle_time 10;

--需要重启下oracle