def METHOD_NAME(aggregator, instance):
    ibmdb2 = IbmDb2Check('ibm_db2', {}, [instance])
    conn1 = mock.MagicMock()
    ibmdb2._conn = conn1
    def mock_exception(*args, **kwargs):
        raise ConnectionError("[IBM][CLI Driver] CLI0106E  Connection is closed. SQLSTATE=08003")
    with mock.patch('ibm_db.exec_immediate', side_effect=mock_exception):
        with mock.patch('ibm_db.connect', return_value=mock.MagicMock()):
            with pytest.raises(ConnectionError, match='CLI0106E  Connection is closed. SQLSTATE=08003'):
                ibmdb2.check(instance)
        # new connection made
        assert ibmdb2._conn != conn1
    aggregator.assert_service_check(IbmDb2Check.SERVICE_CHECK_CONNECT, IbmDb2Check.OK)