@Override
  void initialCriticalMembers(boolean localMemoryIsCritical,
      Set<InternalDistributedMember> criticalMembers) {
    Set<InternalDistributedMember> others = getCacheDistributionAdvisor().adviseGeneric();
    for (InternalDistributedMember idm : criticalMembers) {
      if (others.contains(idm)) {
        addCriticalMember(idm);
      }
    }
  }
@return a random persistent replicate, null if there is none
geode-core/src/main/java/org/apache/geode/internal/cache/DistributedRegion.java