About Latency protection when Primary and Secondary are disconnected

Primary and Secondary are said to be disconnected when they are in the paused state or are disconnected because of a network outage, or an outage of the Secondary node.

latencyprot=override

VVR allows the number of writes in the SRL to exceed the latency_high_mark. In this case, VVR causes latency protection to be overridden and allows incoming writes from the application whose data is being replicated. VVR does not stall incoming writes because the SRL is currently not draining and incoming writes may be stalled indefinitely. Stalling of incoming writes is undesirable for the writing application. Most system administrators set latencyprot=override.

If replication is paused and not resumed, or if there is an extended network outage, the outstanding writes can exceed the latency high mark. When the Secondary reconnects either because replication is resumed or the network becomes available, VVR starts stalling writes until the writes in the SRL reach the latency low mark. The time required for the Primary to send the accumulated writes to the Secondary can take a long time depending on the amount of data to be sent and the bandwidth of the network. The application perceives this as VVR being unresponsive and some applications may time out resulting in application error.

latencyprot=fail

If the number of writes in the SRL reaches the latency_high_mark while the Primary and the Secondary are disconnected, VVR causes new writes at the Primary to fail. This prevents the Secondary from falling further behind than specified by the latency_high_mark.