查看数据库监听状态不对
$ lsnrctl status
[ora11g@upright92 admin]$ lsnrctl start
LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 04-JUN-2016 10:25:14
Copyright (c) 1991, 2013, Oracle.  All rights reserved.

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
TNS-12541: TNS:no listener
 TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 111: Connection refused

然后手动启动数据库报如下错误：

$ lsnrctl start
LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 04-JUN-2016 10:25:14
Copyright (c) 1991, 2013, Oracle.  All rights reserved.
Starting /home/ora11g/u01/oracle/bin/tnslsnr: please wait...
TNSLSNR for Linux: Version 11.2.0.4.0 - Production
System parameter file is /home/ora11g/u01/oracle/network/admin/listener.ora
Log messages written to /home/ora11g/u01/diag/tnslsnr/upright92/listener/alert/log.xml
Error listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
TNS-12542: TNS:address already in use
 TNS-12560: TNS:protocol adapter error
  TNS-00512: Address already in use
   Linux Error: 98: Address already in use

Listener failed to start. See the error message(s) above...

明明监听没启动起，却说已经在运行了，此问题一般是HOSTS文件设置有问题，查看主机名和hosts文件，两个IP地址指向了同一个主机名，将一台主机删除后，再启动监听，一切OK。

用root用户进行修改：
# cat /etc/hosts
# Internet Address      Hostname        # Comments
# 192.9.200.1          net0sample      # ethernet name/address
# 128.100.0.1          token0sample    # token ring name/address
# 10.2.0.2              x25sample      # x.25 name/address
# 2000:1:1:1:209:6bff:feee:2b7f        ipv6sample      # ipv6 name/address
127.0.0.1              loopback localhost      # loopback (lo0) name/address
192.168.101.189  test
192.168.101.190  test

再次启动监听：
$ lsnrctl start
LSNRCTL for IBM/AIX RISC System/6000: Version 10.2.0.5.0 - Production on 05-NOV-2012 08:58:47
Copyright (c) 1991, 2010, Oracle.  All rights reserved.
Starting /oracle/product/10.2.0/db_1/bin/tnslsnr: please wait...
TNSLSNR for IBM/AIX RISC System/6000: Version 10.2.0.5.0 - Production
System parameter file is /oracle/product/10.2.0/db_1/network/admin/listener.ora
Log messages written to /oracle/product/10.2.0/db_1/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=test)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC0)))
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                    LISTENER
Version                  TNSLSNR for IBM/AIX RISC System/6000: Version 10.2.0.5.0 - Production
Start Date                05-NOV-2012 08:58:49
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level              off
Security                  ON: Local OS Authentication
SNMP                      ON
Listener Parameter File  /oracle/product/10.2.0/db_1/network/admin/listener.ora
Listener Log File        /oracle/product/10.2.0/db_1/network/log/listener.log
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=test)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC0)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
总结：/etc/hosts文件设置很重要，这里设置不正确，很多地方都要出错，特别是RAC，会报很多奇怪的错误，配置的时候要多注意。