If a cluster is removed from the XDCR cluster permanently, by resetting the DR role, or through exclusion by the other clusters, it is still possible to rejoin that cluster to the XDCR network. To do that you must reinitialize the cluster and, if it was forcibly excluded, remove the exclusion from the current members of the network. (Note, the following procedure is not necessary if the cluster was removed temporarily by setting the number of replicas to zero.)

First, if the cluster was forcibly removed by exclusion, you must remove the exclusion from the current members of the XDCR network by clearing the cluster.clusterSpec.dr.excludeClusters property (removing the missing cluster's ID from the array):

--set cluster.clusterSpec.dr.excludeClusters=null

Then you must restart the cluster you want to rejoin, reinitializing the cluster's contents with the cluster.clusterSpec.initForce property and setting the appropriate properties (such as the DR role and connection properties):

--set cluster.clusterSpec.initForce=TRUE
--set cluster.config.deployment.dr.role="xdcr"
--set cluster.clusterSpec.replicas=3

Once the cluster rejoins the XDCR network and synchronizes with the current members, be sure to reset the cluster.clusterSpec.initForce property to false.