private static String getId() {
    synchronized (DmidMutex) {
      InternalDistributedSystem ids = InternalDistributedSystem.getAnyInstance();
      if (ids == null) {
        throw new DistributedSystemDisconnectedException("No distributed system");
      }
      if (ids == IdsForId) {
        return DMid;
      }
      IdsForId = ids;
      DistributionManager dm = ids.getDistributionManager();
      DMid = dm.getId().toString();
      return DMid;
    }
  }
Read current {@link #DMid} and return it

@return current DMid
geode-core/src/main/java/org/apache/geode/internal/jta/GlobalTransaction.java