public Map<T, Long> getTombstoneGCVector() {
    Map<T, Long> result;
    synchronized (memberToGCVersion) {
      result = new HashMap<>(memberToGCVersion);
    }
    if (localGCVersion.get() != 0) {
      result.put(myId, localGCVersion.get());
    }
    return result;
  }
Retrieve a collection of tombstone GC region-versions
geode-core/src/main/java/org/apache/geode/internal/cache/versions/RegionVersionVector.java