code: public void markTransactionError() {
  
          final boolean isTracingEnabled = TraceComponent.isAnyTracingEnabled();
  
          if (isTracingEnabled && tc.isDebugEnabled()) {
              Tr.debug(this, tc, "TransactionError occurred on MCWrapper:" + toString());
          }
  
          _transactionErrorOccurred = true;
  
      }
docs: Indicates that an error has occurred from the transaction service. At which point
  we know that the MCWrapper is no longer usable and will be destroyed when the MCWrapper
  is returned to the pool.
  
  If the pool needs to be purged as a result of the transaction error, we rely on the
  ResourceAdapter to fire a ConnectionErrorEvent.