The JDG admin guide has a section for recovering from successive crashed nodes, but doesn't actually give instructions for how to do so (manual intervention is required).

https://access.redhat.com/documentation/en-us/red_hat_jboss_data_grid/7.1/html/administration_and_configuration_guide/handling_network_partitions_split_brain#detecting_and_recovering_from_successive_crashed_nodes

The upstream docs include much more detail on this topic that should be included in the JDG docs.
http://infinispan.org/docs/stable/user_guide/user_guide.html#successive-node-failures