Oracle 11gr2 RAC到单实例的DG搭建
https://www.cnblogs.com/dc-chen/p/9025872.html
https://blog.csdn.net/zx_canway/article/details/72768105
ORACLE 11g RAC-RAC DG Duplicate 搭建（生产操作文档）
https://www.cnblogs.com/hmwh/p/8572876.html
https://www.cnblogs.com/houzhiqing/p/6796567.html
oracle DG 主备库为RAC及一个主库对多个从库的实验环境搭建
http://blog.51cto.com/7642644/1670264
