配置好rac后,兩個節點用tnsping都可以ping通,但用sqlplus連接都出現以下錯誤,不知道哪里出了問題
[oracle@rac2 admin]$ lsnrctl status
LSNRCTL for Linux: Version 9.2.0.4.0 - Production on 04-MAR-2008 08:32:26
Copyright (c) 1991, 2002, Oracle Corporation.  All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac2)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 9.2.0.4.0 - Production
Start Date                04-MAR-2008 08:29:03
Uptime                    0 days 0 hr. 3 min. 22 sec
Trace Level               off
Security                  OFF
SNMP                      OFF
Listener Parameter File   /home/oracle/9.2.0.4/network/admin/listener.ora
Listener Log File         /home/oracle/9.2.0.4/network/log/listener.log
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rac2)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "esal" has 2 instance(s).
  Instance "rac1", status READY, has 1 handler(s) for this service...
  Instance "rac2", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@rac2 admin]$ lsnrctl service
LSNRCTL for Linux: Version 9.2.0.4.0 - Production on 04-MAR-2008 08:32:32
Copyright (c) 1991, 2002, Oracle Corporation.  All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac2)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0
         LOCAL SERVER
Service "esal" has 2 instance(s).
  Instance "rac1", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0 state:ready
         REMOTE SERVER
         (address=(protocol=tcp)(host=rac1)(port=1521))
  Instance "rac2", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0 state:ready
         LOCAL SERVER
The command completed successfully
[oracle@rac2 admin]$ sqlplus cy/zh@esal
SQL*Plus: Release 9.2.0.4.0 - Production on Tue Mar 4 08:32:45 2008
Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.
ERROR:
ORA-12154: TNS:could not resolve service name

Enter user-name:
ERROR:
ORA-01017: invalid username/password; logon denied

Enter user-name: cy/zh@rac1
ERROR:
ORA-12154: TNS:could not resolve service name

SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus
[oracle@rac2 admin]$ sqlplus cy/zh@rac2
SQL*Plus: Release 9.2.0.4.0 - Production on Tue Mar 4 08:32:59 2008
Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.
ERROR:
ORA-12154: TNS:could not resolve service name

Enter user-name:

按照如下過程，一般都能解決：
在虛擬機內開cmd，用lsnrctl status查看監聽器監聽的服務
如看到監聽服務“orcl”，那在本機的tns配置中(SERVICE_NAME = orcl)必須寫orcl；如果想要自定義，則在虛擬機內的listener配置中就要加入自定義服務名，記得要重啟監聽服務：lsnrctl reload
最后形成的配置文件如下
虛擬機listener：

SID_LIST_LISTENER =  (SID_LIST =   (SID_DESC =    (GLOBAL_DBNAME = test)   自定義服務名    (ORACLE_HOME = E:oracleproduct10.2.0db_1) db_home    (SID_NAME = test)     )   (SID_DESC =    (PROGRAM = extproc)    (SID_NAME = PLSExtProc)    (ORACLE_HOME = E:oracleproduct10.2.0db_1) ##這個服務保證你可以使用外部過程，如C程序   )  )

本機tns：

ORCL_XNJ =  (DESCRIPTION =   (ADDRESS_LIST =    (ADDRESS = (PROTOCOL = TCP)(HOST = 182.12.15.232)(PORT = 1521))   )   (CONNECT_DATA =    (SERVICE_NAME = test) 與自定義服務名對應   )  )

再次連接，問題解決！
記住，一定從最簡單的原因找起，不要一上去就看到網上的什么改process數、注冊表之類的，要想想本機能連為什么通過網絡就不行，還是定位問題。
VS2008連接oracle 出現錯誤 ora-12154 tns 無法解析指定的連接標示符

在保證你的代碼沒有錯誤的前提下：
（一）檢查OracleOraDb10g_home1TNSListener 服務有沒有啟動，即監聽服務
（二）檢查tnsnames.ora是否添加連接串（建議用SQLPLUS或者pl/sql測試），其路徑一般是：%Oracle_home%product10.2.0db_1NETWORKADMINtnsnames.ora

其它網友的補充：

今天裝oracle安裝都完成了，但出現了“ORA-12154 TNS”的錯誤，最開始以為是oracle安裝處了問題，但后來發現并不是，因為用SQL Plus可以登錄，只是用plsql登錄時才出現這錯，用360完全卸載了qlsql后，從新裝了次，還是那錯，郁悶。。。后來又把數據庫刪掉重新建立，還是不行，整了半天，最后自己都整暈了，算了，重頭再來吧。。。
百度下很多安裝圖解，按著來就成

oracle服務端安裝圖解
http://www.49028c.com/article/108555.htm
oracle客戶端安裝圖解
http://www.49028c.com/article/108556.htm

oracle完全卸載
http://www.49028c.com/article/96395.htm
或者直接在注冊表中按F3搜索oracle，刪除注冊文件，不過貌似文件有點多，操作有點慢，建議用上邊鏈接的方法

總結了下要注意的幾點

1.安裝服務端是一般選“基本安裝”就行
2.使用PLSQL Developer時,“ORA-12154 TNS無法解析指定的連接標識符”的問題
安裝時報后邊的錯“warning some oracle net versions cannot connect from a path with parentheses”，這錯原來提示了，不能有括號，修改了安裝路徑就沒有問題了
相應的上邊的“ORA-12154 TNS無法解析指定的連接標識符”錯也沒啦，有點暈，沒整明白，但確實好啦
3.“ORA-12154 TNS無法解析指定的連接標識符”按照網上的方法有兩種，但我試了，在我這都不好使，下邊貼出來，沒準兒啥時候可以用
1.解決辦法，修改PLSQL Developer的選項設置：
 
客戶端、服務器端Oracle軟件裝好之后，用PLSQL Devloper登錄時，點擊取消，進入PLSQL Developer主界面，菜單Tools-Preferences，在設置窗口中，選擇Oracle-Connection，對應設置窗口中，找到Oracle Home，選擇OraDb10g_home1，保存設置，重新登錄PLSQL Developer即可

2.修改D:/oracle/product/10.2.0/db_1/NETWORK/ADMIN路徑下的tnsnames.ora文件
###### 一般的配置 ##################################

ORALOCAL = (DESCRIPTION =  (ADDRESS_LIST =   (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))  )  (CONNECT_DATA =   (SERVER = DEDICATED)   (SERVICE_NAME = oralocal)  ) )

以上答案供參考