sqlplus登录提示：ORA-12162：TNS:net service name is incorrectly specified错误

[root@localhost ~]# su - oracle

[oracle@localhost ~]$ sqlplus '/as sysdba'



SQL*Plus: Release 11.2.0.1.0 Production on Tue Apr 22 17:10:52 2014





Copyright (c) 1982, 2009, 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

[oracle@localhost ~]$ export ORACLE_SID=PROD    //向环境变量中加入实例名。说明需手动设置

[oracle@localhost ~]$ sqlplus '/as sysdba'



SQL*Plus: Release 11.2.0.1.0 Production on Tue Apr 22 17:11:16 2014



Copyright (c) 1982, 2009, Oracle.  All rights reserved.



Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options



SQL> select status,instance_name from v$instance;  //登录后查询状态,正常



STATUS       INSTANCE_NAME

------------ ----------------

OPEN         PROD