From the excellent site about the excavations I quote "The function of the Oikoi Building is not evident. It has been supposed that it served as a building for the priests of the sanctuary and as an archive, maybe a prytaneion (council house). It may also have served for ritual meals, in the same way as the two andrones and the East Stoa. A main purpose of the Oikoi Building may, however, have been as a treasury for the safe-keeping of valuable gifts to the god. "