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**Required bandwidth = ((Redo rate in Megabytes per sec. / 0.70) * 8) = bandwidth in Mbps** **Example:** * Redo rate is 3MB/s. * TCP/IP network overhead is 30%. * Required bandwidth = (3/0.7 * 8) = 34.29 Mbps **Note:** * The bandwidth requirement may increase by 3x if future growth is considered. * Other subjective factors, such as customer body size and IT budget, also play a role in determining the required bandwidth.

正文

MOS有篇文章：
How To Calculate The Required Network Bandwidth Transfer Of Redo In Data Guard Environments (Doc ID 736755.1)

还提供了一个参考公式：

The formula used (assuming a conservative TCP/IP network overhead of 30%) for calculating the network bandwidth is :
Required bandwidth = ((Redo rate in Megabytes per sec. / 0.70) * 8)= bandwidth in Mbps

这个逻辑非常简单，比如客户Redo生成速率是：3MB/s，那么按照这个公式就是：
那么带宽就是：3/0.7 *8 = 34.29 Mbps。

如果考虑到未来增长，假设3倍增长，则所需带宽为 34.29*3 = 102.87 Mbps，也就是说至少申请100Mbps的带宽。
其实这里面除了redo速率可以根据现有业务查询得到，其他的都存在一定的主观因素。
比如有的客户体量很小，IT预算紧张，那么就不考虑过多的业务增长，先满足当下要求，等业务增长后再申请扩容。
有的客户后期扩容流程复杂，则考虑前期尽可能申请更多的带宽，应对后期可能的业务增长需求。