ORA-12162: TNS:net service name is incorrectly specified

今天在进行修改oracle_sid环境变量的时候，将相关的环境变量值去掉，从而不能进入sqlplus，报错如下：

[oracle@kel ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jun 8 19:19:21 2014

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

ERROR:
ORA-12162: TNS:net service name is incorrectly specified

Enter user-name:
ERROR:
ORA-12162: TNS:net service name is incorrectly specified

Enter user-name:
ERROR:
ORA-12162: TNS:net service name is incorrectly specified

SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus

查看错误信息：

[oracle@kel ~]$ oerr ora 12162
12162, 00000, "TNS:net service name is incorrectly specified"
// *Cause:  The connect descriptor corresponding to the net service name in
// TNSNAMES.ORA or in the directory server (Oracle Internet Directory) is
// incorrectly specified.
// *Action: If using local naming make sure there are no syntax errors in
// the corresponding connect descriptor in the TNSNAMES.ORA file. If using
// directory naming check the information provided through the administration
// used for directory naming.

错误信息里描述的是：指定的连接字符串错误，服务名称出错，从而使用netmgr命令来检查连接字符串的正确性：

[oracle@kel ~]$ netmgr

在这里可以测试连接字符串是否出错，但是在这里我测试是失败的，从而查看1521端口是否启动监听：

[oracle@kel ~]$ netstat -tnlp
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 0.0.0.0:37667               0.0.0.0:*                   LISTEN      5140/ora_d000_orcl
tcp        0      0 0.0.0.0:111                 0.0.0.0:*                   LISTEN      -   

从而可以看到1521端口未启动监听，从而查看监听的状态：

[oracle@kel ~]$ lsnrctl status

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 08-JUN-2014 19:31:45

Copyright (c) 1991, 2005, 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

在这里看到监听是未启动的状态，从而打开数据库监听：

[oracle@kel ~]$ lsnrctl start

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 08-JUN-2014 19:31:49

Copyright (c) 1991, 2005, Oracle.  All rights reserved.

Starting /home/oracle/product/10.2.0/db_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Log messages written to /home/oracle/product/10.2.0/db_1/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=kel)(PORT=1521)))

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date                08-JUN-2014 19:31:50
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Log File         /home/oracle/product/10.2.0/db_1/network/log/listener.log
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=kel)(PORT=1521)))
The listener supports no services
The command completed successfully

再次测试，发现是可以成功连接的，从而利用连接字符串来连接服务器：

[oracle@kel ~]$ sqlplus system/orcl@orcl

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jun 8 19:34:53 2014

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

发现使用连接字符串是可以连接数据库的，再次使用本地进行连接发现还是不可以的，如下：

[oracle@kel ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jun 8 19:45:49 2014

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

ERROR:
ORA-12162: TNS:net service name is incorrectly specified

最后查看环境变量ORACLE_SID的值：

[oracle@kel ~]$ echo $ORACLE_SID

[oracle@kel ~]$ 

发现环境变量未设置，从而导致连接出错，将ORACLE_SID设置为数据库实例名称：

[oracle@kel ~]$ export ORACLE_SID=orcl
[oracle@kel ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jun 8 19:48:51 2014

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> 

当将环境变量ORACLE_SID的值设置为正确的值的时候，发现已经可以连接。