If you want to remove a cluster from the XDCR environment permanently, you want to make sure it sends all of its completed transactions to the other clusters before it shuts down. You do this by setting the DR role to "none" to perform an orderly shutdown:

--set cluster.config.deployment.dr.role="none"
--set cluster.clusterSpec.replicas=0

Of course, you do not have to shut the cluster down. You can simply remove it from the XDCR environment. Note that if you do so, the data in the current cluster will diverge from those clusters still participating in XDCR. So only do this if you are sure you want to maintain a detached copy of the data:

--set cluster.config.deployment.dr.role="none"

Finally, if you cannot perform an orderly removal from XDCR — for example, if one of the other clusters is offline or if sending the outstanding transactions will take too long and you are willing to lose that data — you can set the property cluster.clusterSpec.dr.forceDrop to "TRUE" to force the cluster to drop out of the XDCR mesh without finalizing its XDCR transfers. Once the cluster has been removed, it is advisable to reset this property to "FALSE" so future procedures revert to the orderly approach of flushing the queues.

--set cluster.clusterSpec.dr.forceDrop=TRUE
--set cluster.config.deployment.dr.role="none"
--set cluster.clusterSpec.replicas=0
 . . .
--set cluster.clusterSpec.dr.forceDrop=FALSE