Oracle技术之连接RAC数据库中单个实例（一）

有时候希望连接RAC数据库时，只连接到其中某个实例。但是要实现这个目的，并不是仅仅通过设置TNSNAMES.ORA中服务名地址列表就可以实现的。

这篇描述通过INSTANCE_NAME来实现目标。

测试环境10.2.0.3 Rac for Solaris for sparc 64：

SQL> SELECT NAME FROM V$DATABASE;

NAME

---------

TESTRAC

SQL> SELECT INSTANCE_NUMBER, INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NUMBER INSTANCE_NAME

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

             1 testrac1

SQL> SELECT INSTANCE_NUMBER, INSTANCE_NAME FROM GV$INSTANCE;

INSTANCE_NUMBER INSTANCE_NAME

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

             1 testrac1

             2 testrac2

为了避免出现ORA-12545错误，在两个节点分别设置了LOCAL_LISTENER初始化参数：

SQL> ALTER SYSTEM

 2  SET LOCAL_LISTENER = '(ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.224)(PORT = 1521))'

 3  SID = 'testrac1';

系统已更改。

节点2：

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac2

SQL> ALTER SYSTEM

 2  SET LOCAL_LISTENER = '(ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.225)(PORT = 1521))'

 3  SID = 'testrac2';

系统已更改。

分别检查两个节点上LISTENER相关的配置，节点1：

SQL> SHOW PARAMETER LISTENER

NAME             TYPE        VALUE

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

local_listener  string      (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.224)(PORT = 1521))

remote_listener string      LISTENERS_TESTRAC

节点2：

SQL> SHOW PARAMETER LISTENER

NAME             TYPE        VALUE

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

local_listener   string      (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.225)(PORT = 1521))

remote_listener  string      LISTENERS_TESTRAC

其中REMOTE_LISTENER设置的值是TNSNAMES.ORA中配置的服务名，节点1上的TNSNAMES.ORA配置为：

LISTENER_TESTRAC2 =

 (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

LISTENER_TESTRAC1 =

 (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

TESTRAC2 =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

     (INSTANCE_NAME = testrac2)

   )

 )

TESTRAC1 =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

     (INSTANCE_NAME = testrac1)

   )

 )

TESTRAC =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

   (LOAD_BALANCE = yes)

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

   )

 )

LISTENERS_TESTRAC =

 (ADDRESS_LIST =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

 )

节点2上的TNSNAMES.ORA配置为：

LISTENER_TESTRAC2 =

 (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

LISTENER_TESTRAC1 =

 (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

TESTRAC2 =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

     (INSTANCE_NAME = testrac2)

   )

 )

TESTRAC1 =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

     (INSTANCE_NAME = testrac1)

   )

 )

TESTRAC =

 (DESCRIPTION =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

   (LOAD_BALANCE = yes)

   (CONNECT_DATA =

     (SERVER = DEDICATED)

     (SERVICE_NAME = testrac)

   )

 )

LISTENERS_TESTRAC =

 (ADDRESS_LIST =

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip)(PORT = 1521))

   (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-vip)(PORT = 1521))

 )

在本地测试连接，本地TNSNAMES.ORA文件中TESTRAC服务名配置为：

TESTRAC =

 (DESCRIPTION =

   (ADDRESS_LIST =

     (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.224)(PORT = 1521))

     (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.225)(PORT = 1521))

   )

   (CONNECT_DATA =

     (SERVICE_NAME = TESTRAC)

   )

 )

下面尝试多次连接TESTRAC数据库，检查每次连接到哪个实例上：

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac1

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac2

将TESTRAC配置中的地址去掉一个，结果仍然如此：

TESTRAC =

 (DESCRIPTION =

   (ADDRESS_LIST =

     (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.224)(PORT = 1521))

   )

   (CONNECT_DATA =

     (SERVICE_NAME = TESTRAC)

   )

 )

测试连接：

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac1

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac2

可以看到，即使TNSNAMES.ORA中配置了一个节点的地址，通过这个服务名访问RAC数据库，还是可能连接到两个实例上的。

为了确保通过服务名只连接到一个实例，需要在CONNECT_DATA中不仅仅指定SERVICE_NAME，同时还需要指定INSTANCE_NAME参数：

TESTRAC =

 (DESCRIPTION =

   (ADDRESS_LIST =

     (ADDRESS = (PROTOCOL = TCP)(HOST = 172.25.198.224)(PORT = 1521))

   )

   (CONNECT_DATA =

     (SERVICE_NAME = TESTRAC)

     (INSTANCE_NAME = TESTRAC1)

   )

 )

现在再次测试连接：

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac1

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac1

SQL> CONN YANGTK/YANGTK@TESTRAC

已连接。

SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;

INSTANCE_NAME

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

testrac1

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