code: public void cancelTransaction ()
      {
          if (_tevent == null) {
              String errmsg = "Cannot cancel: not involved in a transaction [dobj=" + this + "]";
              throw new IllegalStateException(errmsg);
          }
  
          // if we're in a nested transaction, make a note that it is to be cancelled when all
          // parties commit and decrement the nest count
          if (_tcount > 0) {
              _tcancelled = true;
              _tcount--;
  
          } else {
              _tevent.cancel();
          }
      }
docs: Cancels the transaction in which this distributed object is involved.
  
  @see CompoundEvent#cancel