def DT_2(dul):
    """Data transfer DT-2.

    On receiving a P-DATA-TF request, send P-DATA indication

    State-event triggers: Sta6 + Evt10

    References
    ----------
    1. DICOM Standard 2015b, PS3.8, Table 9-7, "Associate Establishment
       Related Actions"

    Parameters
    ----------
    dul : pynetdicom.dul.DULServiceProvider
        The DICOM Upper Layer Service instance for the local AE

    Returns
    -------
    str
        Sta6, the next state of the state machine
    """
    dul.assoc.dimse.receive_primitive(dul.primitive)
    return 'Sta6'
