WARNING: Subscription for node down event still pending
以前没在意，今天查了一下，原来是因为 10G 中的 ONS，可以通过配置 listener 的参数
SUBSCRIBE_FOR_NODE_DOWN_EVENT=OFF 屏蔽掉，对 listener 的功能没有影响。
Listener Subscription for ONS Node Down Event Information
Listener will subscribe to the Oracle Notification Service (ONS) node down event on startup if ONS configuration file is available. This subscription enables the listener to remove the affected service when it receives node down event notification from ONS. The listener uses asynchronous subscription for the event notification. The following warning message will be recorded to listener log file on each STATUS command if the subscription has not completed; for example if the ONS daemon is not running on the host.
WARNING: Subscription for node down event still pending
Listener will not be able to receive the ONS event while subscription is pending. Other than that, no other listener functionality is affected.
参考：
http://dba-services.berkeley.edu/docs/oracle/manual-10gR2/network.102/b14212/troublestng.htm
http://www.freelists.org/archives/oracle-l/01-2005/msg01111.html