当连接异常时，可以通过分析监听日志来查找线索
~ [DBCHC]$ find $ORACLE_HOME -name listener.log
/opt/64bit/oracle/11.2.0/log/diag/tnslsnr/sinrndvud062/listener/trace/listener.log
在RAC环境中，需要切换到grid用户来查询监听日志
vgerndpud852: / # su - grid
/home/ora11grid[FRWK]:find $ORACLE_HOME -name listener.log
find: `/opt/ora11grid/crf/admin/run/crflogd': Permission denied
find: `/opt/ora11grid/crf/admin/run/crfmond': Permission denied
/opt/ora11grid/log/diag/tnslsnr/vgerndpud852/listener/trace/listener.log
/home/ora11grid[FRWK]:lsnrctl
LSNRCTL for Linux: Version 11.2.0.3.0 - Production on 17-NOV-2016 04:28:53
Copyright (c) 1991, 2011, Oracle. All rights reserved.
Welcome to LSNRCTL, type "help" for information.
LSNRCTL> show
The following operations are available after show
An asterisk (*) denotes a modifier or extended command:
rawmode displaymode
rules trc_file
trc_directory trc_level
log_file log_directory
log_status current_listener
inbound_connect_timeout startup_waittime
snmp_visible save_config_on_stop
dynamic_registration enable_global_dynamic_endpoint
oracle_home pid
connection_rate_limit
LSNRCTL> show log_status
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
LISTENER parameter "log_status" set to ON
The command completed successfully