1、啟動監聽：
[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、這個問題基本2個原因導致 ：
1, /etc/hosts 文件中的 ip和主機名不一致
2, listener.ora 中監聽主機非當前主機.
3、改好后關閉監聽在重啟監聽
