Restarting dead background process QMNC一例

一套10.2.0.5 的数据库,告警日志中反复出现”Restarting dead background process QMNC”的信息,具体日志如下:

 

 

Thu Jun 07 10:38:28 GMT 2012
Restarting dead background process QMNC
QMNC started with pid=271, OS id=17059
Thu Jun 07 10:43:08 GMT 2012
Restarting dead background process QMNC
QMNC started with pid=234, OS id=18263

 

但是通过ps 命令查看 重启的QMNC进程很快又消失掉,

Metalink Note Restarting dead background process QMNC recorded in the alert.log file [ID 395137.1]说明了该问题

 

Applies to:
Oracle Server - Enterprise Edition - Version: 10.1.0.2 to 11.2.0.2 - Release: 10.1 to 11.2
Information in this document applies to any platform.
Checked for currency 06-Sep-10
Symptoms
The following messages are recorded in the alert log every 5 minutes

Restarting dead background process QMNC
Changes
Cause

1. database startup :

The database has not opened for an undetermined reason, i.e there is no statement:

Completed: ALTER DATABASE OPEN

recorded in the alert.log file.

2. database shutdown :

A process may be preventing the database from shutting down
cleanly. As a consequence, this may be causing the qmnc process problems.
Solution

This is expected behaviour.

The reason why the database has not opened or shutdown should be investigated.

These messages are a symptom of the problem and not the underlying cause.

 

该问题除了会在 alert.log中每五分钟生成一次 “Restarting dead background process QMNC”的信息外,不会造成其他影响,一般可以忽略。

 

该警告信息可能由于ORACLE INSTANCE未能正常关闭引起(即shutdown不是clean干净的), 查询之前的alert.log 发现有一个EMN0进程在上一次shutdown immediate时被启动,且一直存在着:

 

Starting background process EMN0
Wed Jun 06 19:30:26 GMT 2012
Shutting down instance: further logons disabled
EMN0 started with pid=47, OS id=322

 

EMN0是一个高级队列advanced Queuing相关的进程,该进程不是关键后台进程 , 必须时可以被 KILL掉

 

The EMNO process is new to Oracle8i, and has to do with improvements made to Advanced
Queuing, specifically:

A combination of features are introduced to allow a publish/subscribe style of  messaging
between applications. These features include rule-based subscribers,
message propagation, the listen feature and notification capabilities.

OCI functions are available to register a callback for message notification.  This
interface is only valid for the asynchronous mode of message delivery. In this mode, a
subscriber issues a registration call which specifies a callback.  When messages are
received that match the subscription criteria, the callback
is invoked.  A new background process event monitor (EMON) is used to notify the
subscriber.  This process is started automatically when the first notification is issued
for the instance.  The application may then issue an explicit message_receive(dequeue) to
retrieve the message.

This functionality is triggered with the OCI call OCISubscriptionRegister. OCI clients
can use the new call OCISubscriptionRegister to register a callback for
message notification. The client issues a registration call which specifies a
subscription name and a callback. When messages for the subscription are received, the
callback is invoked. The callback may then issue an explicit dequeue to retrieve the
message.

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