oracle - TNS 条目将指向辅助数据库以防主数据库关闭

Question

我有两个彼此同步的 RAC 数据库。我们使用的应用程序只从数据库中读取。我们想提出一个 TNS 条目，它将首先尝试登录到主 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，并且有一个同名的服务正在运行。

同样，当主 RAC 可访问时，应用程序不应连接到辅助 RAC。

提前致谢 ... ：）

主 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)
     )
    )
  )

并且辅助 RAC TNS 是

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)
      )
    )
  )