1、启动监听：
[oracle@admin ~]$ lsnrctl start
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 15-MAR-2020 12:44:31
Copyright (c) 1991, 2009, Oracle. All rights reserved.
TNS-01106: Listener using listener name LISTENER has already been started
2、这个问题基本2个原因导致 ：
1, /etc/hosts 文件中的 ip和主机名不一致
2, listener.ora 中监听主机非当前主机.
3、改好后关闭监听在重启监听
