ORA-12560: TNS:protocol adapter error(TNS:協議適配器...

這種問題通常是由於客戶端不知道要連那個instance或者不知道要使用哪一個TNS Alias

可能的緣由1.服務沒有起來
下邊是Tom的一個Test Case來講明OracleServiceSID服務沒有起來的話，是會引發ORA-12560錯誤的。
[plain] view plaincopyprint?
C:\Documents and Settings\tkyte>sqlplus scott/tiger 
 
SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:43:55 2007 
 
Copyright (c) 1982, 2005, Oracle.  All rights reserved. 
 
 
Connected to: 
Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production 
With the Partitioning, OLAP and Data Mining options 
 
scott%ORA10GR1> exit 
Disconnected from Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production 
With the Partitioning, OLAP and Data Mining options 
 
C:\Documents and Settings\tkyte>net stop oracleserviceora10gr1 
The OracleServiceORA10GR1 service is stopping......... 
The OracleServiceORA10GR1 service was stopped successfully. 
 
 
C:\Documents and Settings\tkyte>sqlplus scott/tiger 
 
SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:44:35 2007 
 
Copyright (c) 1982, 2005, Oracle.  All rights reserved. 
 
ERROR: 
ORA-12560: TNS:protocol adapter error 
 
 
Enter user-name: 
ERROR: 
ORA-12560: TNS:protocol adapter error 
 
 
Enter user-name: 
ERROR: 
ORA-12560: TNS:protocol adapter error 
 
 
SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus 
 
C:\Documents and Settings\tkyte>net start oracleserviceora10gr1 
The OracleServiceORA10GR1 service is starting.......... 
The OracleServiceORA10GR1 service was started successfully. 
 
 
C:\Documents and Settings\tkyte>sqlplus scott/tiger 
 
SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:45:12 2007 
 
Copyright (c) 1982, 2005, Oracle.  All rights reserved. 
 
 
Connected to: 
Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production 
With the Partitioning, OLAP and Data Mining options 
 
scott%ORA10GR1><A name=PAGETOP></A> 

C:\Documents and Settings\tkyte>sqlplus scott/tiger

SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:43:55 2007

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

Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production
With the Partitioning, OLAP and Data Mining options

scott%ORA10GR1> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production
With the Partitioning, OLAP and Data Mining options

C:\Documents and Settings\tkyte>net stop oracleserviceora10gr1
The OracleServiceORA10GR1 service is stopping.........
The OracleServiceORA10GR1 service was stopped successfully.

C:\Documents and Settings\tkyte>sqlplus scott/tiger

SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:44:35 2007

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

ERROR:
ORA-12560: TNS:protocol adapter error

Enter user-name:
ERROR:
ORA-12560: TNS:protocol adapter error

Enter user-name:
ERROR:
ORA-12560: TNS:protocol adapter error

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

C:\Documents and Settings\tkyte>net start oracleserviceora10gr1
The OracleServiceORA10GR1 service is starting..........
The OracleServiceORA10GR1 service was started successfully.

C:\Documents and Settings\tkyte>sqlplus scott/tiger

SQL*Plus: Release 10.1.0.4.0 - Production on Thu Sep 6 15:45:12 2007

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

Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.4.0 - Production
With the Partitioning, OLAP and Data Mining options

scott%ORA10GR1>修改方法：控制面板>管理工具>服務裏邊把OracleServiceSID起起來

可能的緣由2.ORACLE_SID環境變量沒有指定（最多見引發ORA-12560問題的緣由）
檢查方法，命令行(cmd)下，
C:\Documents and Settings\ptian>set oracle_sid
ORACLE_SID=test
ORACLE_SID是sqlplus默認鏈接的數據庫instance,即sqlplus user/pwd鏈接的instance，若是不指定sqlplus裏鏈接的時候就須要明確@你的instance,eg,sqlplus user/pwd@instance .
修改方法：在註冊表中，HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OraDb10g_home1\ORACLE_SID 需指向你的Instance(eg.orcl)；或者在系統的環境變量里加ORACLE_SID項，值爲Instance的SID。

可能的緣由3.TNS_ADMIN環境變量沒有指定
檢查方法，命令行(cmd)下，
C:\Documents and Settings\ptian>set TNS_ADMIN
TNS_ADMIN=D:\oracle\product\10.1.0\Db_1\NETWORK\ADMIN
TNS_ADMIN應該返回你的tnsnames.ora所在的目錄
修改方法：能夠在註冊表HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOME0\TNS_ADMIN或者環境變量中指定。

可能的緣由4.ORACLE_HOME環境變量沒有指定
和上邊的方法相似，檢查Oracle_Home環境變量

可能的緣由5.tnsnames.ora文件內容不對
A sample:
TEST =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = ptian-cn.cn.oracle.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = test)
    )
  )

Possible fixes for the TNS-12560 include：