This article focuses on the Oracle Listener Tracing & Troubleshooting, in this article we would explore the parameters available to enable tracing on Oracle listener so that additional data is available to troubleshoot network related issues between client & server.

To enable Listener tracing add following parameters to listener.ora:-

TRACE_LEVEL_LISTENER=[0-16|USER|ADMIN|SUPPORT|OFF]
#This parameter defines the level of tracing
#OFF (equivalent to 0) disabled - provides no tracing.
#USER (equivalent to 4) traces to identify user-induced error conditions.
#ADMIN (equivalent to 6) traces to identify installation-specific problems.
#SUPPORT (equivalent to 16) trace information required by Oracle Support for troubleshooting. 
TRACE_DIRECTORY_LISTENER=<DIRECTORY> 
#Name of the directory where the tracefiles would be written.
TRACE_TIMESTAMP_LISTENER=TRUE
#A timestamp in the form of [DD-MON-YY 24HH:MI;SS] is recorded against each operation traced by the trace file. 
TRACE_FILE_LISTENER=<FILENAME>
#This parameter defines the name of tracefile which is automatically appended by .TRC

Once the above parameters are added in listener.ora, reload the Oracle Listener (lsnrctl reload) to bring these changes into effect and then study the tracefile generated to identify the issue.

In the next post in this series we would take some TNS issue case studies and identify the issue from the tracefiles.