在遠端客戶端連接RAC數據庫時，通過統一的服務名連接時經常會出現ORA-12545錯誤。在METALINK上查詢了一下，竟是Oracle的一個小bug。
環境：ORACLE 11G R2 RAC數據庫，兩節點。
現象：
[oracle@ted35 ~]$sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on 星期五 6月 15 11:57:00 2012
Copyright (c) 1982, 2010, Oracle. All rights reserved.
SQL> conn sys/ted@123e@prodb as sysdba;
ERROR:
ORA-12545: 因目標主機或對象不存在, 連接失敗
故障分析：用tnsping檢查一下，發現可以ping通，這是因為tnsping只檢查IP地址和端口是否能連通，至於數據庫實例狀態，監聽注冊了哪些服務這些，它是不檢查的。
我們看一下本地數據庫TNSNAMES的配置：
TESTRAC =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))
(LOAD_BALANCE = yes)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = 10.58.12.124)
(FAILOVER_MODE =
(TYPE = SELECT)
(METHOD = BASIC)
(RETRIES = 180)
(DELAY = 5)
)
)
Oracle在文檔Note:364855.1：RAC Connection Redirected To Wrong Host/IP ORA-12545中進行了描述，並給出了解決方法：修改數據庫中的初始化參數LOCAL_LISTENER（注：這種方法在修改初始化參數后，需要重啟監聽，重啟實例）
SQL>conn / as sysdba;
Connected.
SQL> ALTER SYSTEM SET LOCAL_LISTENER = '(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521)) 'SID = 'prodb1';
系統已更改。
登錄另外一個節點
SQL>conn / as sysdba;
Connected.
SQL> ALTER SYSTEM SET LOCAL_LISTENER = '(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))' SID = 'prodb2';
系統已更改。
設置之后，再次嘗試連接數據庫：
SQL> conn sys/ted@123e@prodb as sysdba;
Connected.
SQL> conn sys/ted@789e@prodb as sysdba;
Connected.
修改之后，沒有再次出現同樣的錯誤。
我們也可以通過只修改客戶端hosts文件的方式，來解決這個問題。
首先在linux主機上修改HOSTS文件
root@prodb1 # vi /etc/hosts
#
10.58.12.120 prodb1-public # Public
10.58.12.124 prodb1 # Virtual
23.23.23.120 prodb1-priv # Private
10.58.12.121 prodb2-public # Public
10.58.12.125 prodb2 # Virtual
23.23.23.121 prodb2-priv # Private
10.58.12.126 prodb-scan # SCAN
然后客戶端的tnsnames.ora中的配置如下：
$ more $ORACLE_HOME/network/admin/tnsnames.ora
# tnsnames.ora Network Configuration File: /data/oracle/product/11.2/database/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
LISTENERS_prodb =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))
)
LISTENER_prodb1 =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521))
LISTENER_prodb2 =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))
prodb =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))
(LOAD_BALANCE = yes)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = prodb)
(FAILOVER_MODE =
(TYPE = SELECT)
(METHOD = BASIC)
(RETRIES = 180)
(DELAY = 5)
)
)
)
prodb1 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.124)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = prodb)
(INSTANCE_NAME = prodb1)
)
)
prodb2 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.58.12.125)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = prodb)
(INSTANCE_NAME = prodb2)
)
)
下面嘗試連接遠端RAC數據庫：
SQL> conn sys/ted@123e@prodb as sysdba;已連接。
SQL> conn sys/ted@789e@prodb as sysdba;已連接。
其實在本地hosts文件中加上RAC實例所在服務器的ip和主機名信息，就可以避免這個錯誤。
另外注意在RAC環境中，任何修改都一定要謹慎。RAC 環境一旦安裝好后，主機名就不能隨意修改，除非先刪除節點，修改Hostname，再添加節點。還有一點主機名必須和public名一致，這一點也非常重要。