最近在red hat 6.6虚拟机上安装了Oracle 11gR2数据库，安装完毕，使用没有问题，通过主机也可以访问到虚拟机上的数据库。然而，在重新启动虚拟机后，主机无法访问到数据库，提示错误：
PS C:\Users\13842> sqlplus sys/Lijiaman3102700@orcl as sysdba SQL*Plus: Release 11.2.0.1.0 Production on 星期六 2月 25 16:56:47 2017 Copyright (c) 1982, 2010, Oracle. All rights reserved. ERROR:
ORA-12541: TNS: 无监听程序 请输入用户名:
发现没有监听程序，于是到虚拟机上查看监听器状态，结果如下：
LSNRCTL> status
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 111: Connection refused
发现是监听器没有启动，启动即可：
[oracle@localhost Desktop]$ lsnrctl start LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 25-FEB-2017 18:13:56 Copyright (c) 1991, 2009, Oracle. All rights reserved. Starting /home/app/oracle/product/11.2.0/dbhome_1/bin/tnslsnr: please wait... TNSLSNR for Linux: Version 11.2.0.1.0 - Production
System parameter file is /home/app/oracle/product/11.2.0/dbhome_1/network/admin/listener.ora
Log messages written to /home/app/oracle/diag/tnslsnr/localhost/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=1521))) Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 25-FEB-2017 18:13:56
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /home/app/oracle/product/11.2.0/dbhome_1/network/admin/listener.ora
Listener Log File /home/app/oracle/diag/tnslsnr/localhost/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=1521)))
The listener supports no services
The command completed successfully
启动之后，新的问题又出现了，在倒数第2行，提示：The listener support no services。说明Oracle的服务并没有注册到监听器，这时，使用主机上的客户端连接数据库，会提示错误：
ERROR:
ORA-12514: TNS: 监听程序当前无法识别连接描述符中请求的服务
接下来配置监听服务信息，在虚拟机上打开网络管理界面：
[oracle@localhost Desktop]$ netmgr
出现如下界面，点击Local->Listeners->Listener->Database Services->Add Database：
三个参数设置：
· Global Database Name:
SQL> select * from global_name; GLOBAL_NAME
--------------------------------------------------------------------
ORCL
· Oracle Home Dictionary: Oracle安装路径，一般为：../app/oracle/product/11.2.0/dbhome_1
· SID：默认ORCL
点击File->Save network Configuration。
重启数据库，解决。