code: public void updateLastTimestamp(long tstampMicros)
      {
          while (true)
          {
              long last = lastTimestampMicros.get();
              if (tstampMicros <= last || lastTimestampMicros.compareAndSet(last, tstampMicros))
                  return;
          }
      }
docs: Can be use when a timestamp has been assigned by a query, but that timestamp is
  not directly one returned by getTimestamp() (see SP.beginAndRepairPaxos()).
  This ensure following calls to getTimestamp() will return a timestamp strictly
  greated than the one provided to this method.