Sometimes a man is inspired in a dream by a deity or the spirit of a deceased ancestor or other close relative to hold a sandau hari festival which is bigger than a makai di ruai ceremony. To this feast, the people of the longhouse invite guests from other villages. Gawai Sandau Hari means “day time festival” and is celebrated on the open-air verandah, tanju, only during the daytime.
As soon as the guests have arrived and are received by the hosts along the ruai, the feast chief waves a cock along the longhouse gallery to invite all who have come to be seated upon his tanju which has been decorated for the occasion with good mats and woven blankets to attend his feast.
After all of the guests have taken their seats in order, three to five warriors each make from three to five offerings to God and the spirits. Having done this, one of the warriors stands up with a cock in his hands to recite a long sampi prayer to call for the deities and the universal spirits to come to the feast with blessings and charms of all kinds. He beseeches the almighty God in his mercy to grant to the feast chief and his people good health and prosperity in times to come. After the recitation of this prayer, the young men serve the guests with tuak wine on the tanju. After the guests have drunk the tuak wine, expert drummers perform gendang pampat music on ketebong drums.
As the quick music is booming, three to five warriors perform their ray ah dance around the sacred Kalingkang pole which is carefully raised at the middle of the tanju. At this moment it is believed that Sengalang Burong, the god of war; his sons-in-law, Ketupong, Beragai Bejampong, Embuas, Pangkas, Papau and Nendak; and their wives from the heavens are spiritually present and mingling with the hosts and guests on the tanju.
The music from the drums continues, accompanied by the tinkling sound of iron adzes struck by a chosen warrior. This music is made for Sengalang Burong’s sons-in-law to join the rayah dance spiritually with the warrior dancers. At this time another warrior burns wild flowers and crabs on a hearth to welcome the coming of spiritual guests from the Panggau Libau and Gellong worlds. These guests are Keling, Laja, Simpurai, Pungga, Tutong, Ngelai, Renggan and others.1 If these wild flowers and crabs are not burnt on the hearth (bedilang) the unfortunate human guests would faint (luput – pansa arong) by the presence of these spiritual heroes.
After the dancing ceremony around the sacred pole is over, the spirits are believed to return to their own home. The guests and senior hosts are served food along the open tanju. After the meal is over, the feast chief waves a cock to inform all the people that his sandau hari festival is now coming to an end. As soon as the announcement is made, the guests disperse; some return to their own longhouse immediately, while others continue to drink tuak wine with the hosts till sunset.
Source: http://gnmawar.wordpress.com/adat-iban/part-1-iban-adat-law-and-custom/ Chapter 4 Religious Festivals