In the case of a Primary failure or if the Primary needs to be brought down for some maintenance tasks, the role of the Primary can be taken over by the Secondary. When the original Primary becomes available again you may want to failback to the original Primary. The fast-failback feature enables you to do this quickly and efficiently as it performs incremental synchronization, for only the changed data. This feature uses the DCM of the data volumes of the new Primary to keep track of the changed content and the new content. This process of logging on the DCM after takeover is called failback logging or fast-failback logging.

You can perform the Takeover operation with fast-failback by using the fast-failback logging option on one of the Secondaries. After the Takeover operation is complete, you can start the applications on the new Primary. All the subsequent writes from the applications running on the new Primary are then tracked on the DCM of the new Primary. However, if there are any updates on the Primary that did not reach the Secondary, these may be lost.