select * from dba_objects o where object_type='DATABASE LINK';

drop database link remoteOssc--link名字

select * from risenet_out_user_info@remote

SELECT * FROM GLOBAL_NAME; --查看服务名

create database link remoteOssc  --创建link
             --用户名               --密码
  connect to user identified by pass
  using '(DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = Ip)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = instance)
    )
  )';
select * from risenet_out_user_info@remoteossc