Listener.ora ：WARNING: Subscription for node down event still pending

 今天做实验，发现listener.ora文件里有这个报错：WARNING: Subscription for node down event still pending。

 网上查了一下，大概有如下几种说法：

Issue is fixed in 10.2.0.3 Patch Set
Oracle Support recommends patching to 10.2.0.4 as this the lastest release

- OR -

Apply Patch 4518443 for the problem (if a patch is available)

- OR -

As a workaround, two steps should be done:

1. The following parameter can be added to listener.ora

SUBSCRIBE_FOR_NODE_DOWN_EVENT_=OFF

Where should be replaced with the actual listener name configured in the LISTENER.ORA file. This parameter is to be placed by itself on an empty line / at the end of file.

For example, if the listener name is LISTENER (default), the parameter would be:

SUBSCRIBE_FOR_NODE_DOWN_EVENT_LISTENER=OFF

2. Locate the ons.config file in the 10g(rdbms) home and rename it to something else.
For example:

cd $ORACLE_HOME/opmn/conf
mv ons.config ons.config.orig

The listener needs to be restarted after these changes.

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检查时会发现系统上存在两个监听器进程，其中一个是另外一个的子进程。

检查监听 ps -ef | grep tnslsnr

KILL掉一个子进程，恢复正常

在Metalink上可以找到相关问题的很多解释，这个问题被最终确认为一个BUG，BUG号为：4518443
Oracle称在较大压力下，监听进程可能出现间歇性停止服务，此时Oracle会spaw出另外一个监听进程，进而导致两个监听进程互相影响的故障。