TNS条目将指向辅助数据库的案例主要是关闭

Question

我有两个相互同步的RAC数据库。我们使用的应用程序仅从数据库中读取。我们想要提出一个TNS条目，首先尝试登录主RAC，如果连接失败，它应该连接到辅助RAC 。

两个RAC都已启动并正在运行并且运行的服务名称相同。

再一次，应用程序不应该在主RAC可访问时连接到辅助RAC。

提前致谢...：）

主要RAC TNS条目是

rac1=
  (DESCRIPTION =
    (FAILOVER = ON)
    (ENABLE=BROKEN)
    (LOAD_BALANCE = ON)
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac1-host1)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac1-host2)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = testdb)
      (FAILOVER_MODE =
        (TYPE = SELECT)
        (METHOD = BASIC)
        (RETRIES = 20)
        (DELAY = 2)
     )
    )
  )

和辅助RAC TNS

rac2=
  (DESCRIPTION =
    (FAILOVER = ON)
    (ENABLE=BROKEN)
    (LOAD_BALANCE = ON)
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac2-host1)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac2-host2)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = testdb)
      (FAILOVER_MODE =
        (TYPE = SELECT)
        (METHOD = BASIC)
        (RETRIES = 20)
        (DELAY = 2)
      )
    )
  )