create database link test_link
  connect to xx identified by xx
  using ‘(DESCRIPTION =
  (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.xx.xx.xx7)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.xx.xx.xx6)(PORT = 1521))
      (FAILOVER = on)
      (LOAD_BALANCE = on)
    )
  (CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = ora11g)))‘;




load_balance=on 负载平衡

可以加也可以不加