Specific to standby database(s), we may have performance issues to read redo data and to transport over a network, redo write phase because of bad RAID configurations, Redo Apply phase because of huge redo, improper memory settings, or the issues can be with bugs. Here we will discuss some of them.
Standby databases will be placed geographically in different locations with WAN for high availability in case of a disaster. Even though you keep your standby database geographically far away, you should have reasonable bandwidth to avoid data lag between the primary and standby databases. It can be a bigger problem if you are using synchronous redo with AFFIRM. Consider the use of a high latency network to fulfill redo rate shipping as follows:
Required network bandwidth = ((Redo rate bytes per sec. / 0.7) * 8) / 1,000,000 = bandwidth in Mbps.
By using this formula according to the redo generation rate, you can estimate the required network bandwidth...