建立DBLink

-- Create database link 
CREATE PUBLIC database link link_name(自定义dblink名称)
  connect to user(数据库用户)
  IDENTIFIED BY passwd(数据库密码)
  using '------tns配置-----';

tns配置以下：

eg. (DESCRIPTION =
     (ADDRESS_LIST =
      (FAILOVER=ON)
      (ADDRESS = (PROTOCOL = TCP)(HOST = IP)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = IP)(PORT = 1521))
     )
    (CONNECT_DATA =
     (SERVER = DEDICATED)
     (SERVICE_NAME = orcl)
     )))