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10G LSNR: 'Warning: Subscription For Node Down Event Still Pending' In Listener Log

Applies to:
Oracle Net Services - Version: 10.1.0.2.0 to 11.1.0.7.0
This problem can occur on any platform.
Checked for relevance on 08-JAN-2009.
This issue affects only 10g and newer listeners.


Symptoms
You are receiving the following warning messages in the listener.log file constantly:
'WARNING: Subscription for node down event still pending' 


Changes
This may be a new installation or a recent upgrade to 10g or newer.


Cause
These messages are related to the Oracle TNS Listener's default subscription to the Oracle Notification Service (ONS). In a non-RAC environment it is recommended to disable this subscription.  
This feature was introduced in Oracle 10g.


Solution
Set the following parameter in the listener.ora:
SUBSCRIBE_FOR_NODE_DOWN_EVENT_<listener_name>=OFF

Where <listener_name> should be replaced with the actual listener name configured in the
LISTENER.ORA file.

SUBSCRIBE_FOR_NODE_DOWN_EVENT_<listener_name> parameter is to be placed by istelf on an empty line.

It will be necessary to restart or reload the listener following the addition of this parameter.

This will prevent the messages from being written to the log file and may also prevent the TNS
Listener from hanging periodically.  See Note 340091.1

Please Note: Setting SUBSCRIBE_FOR_NODE_DOWN_<listername> to OFF disables a necessary RAC functionality. The above workaround is recommended only for non-RAC environments.
The issue may be present in all 10g and newer installations.