Oracle Net Logging and Tracing

Server Logging:
By default, the listener is configured to enable the generation of a log file. By default, listener log location is $ORACLE_HOME/network/log/listener.log

To enable server tracing simply click the Tracing Enabled radio button in Oracle Net Manager. Default location is $ORACLE_HOME/network/trace/listener.trc. You can set trace level to OFF, USER, ADMIN, or SUPPORT.

Ex. of listener.ora with logging and tracing parameters enabled

TRACE_LEVEL_LISTENER = ADMIN
TRACE_FILE_LISTENER = LISTENER.trc
TRACE_DIRECTORY_LISTENER = D:\Oracle\sample\network\trace
LOG_DIRECTORY_LISTENER = D:\Oracle\sample\network\LOG
LOG_FILE_LISTENER = LISTENER.log