Domnall is considered to have been an effective ruler who introduced military reforms later credited to Brian Boru.[citation needed] Much of his reign was spent in war against his sister Dúnflaith's husband Amlaíb Cuarán, the King of Dublin. In 980 he abdicated and entered the monastery Armagh where he died shortly afterwards.
Domnall was called "High King of Ireland" (ard-rí Érenn) in his obituary, and was the last of his family to hold the title. He was succeeded by Máel Sechnaill mac Domnaill of Clann Cholmáin.
Domnall's children included Muiredach, whose son Lochlann may have been the ancestor of Domnall Ua Lochlainn, and Muirchertach, ancestor of the O'Neills of Tír Eógain. His grandson Flaithbertach Ua Néill was King of Ailech and the leading figure among the Uí Néill, certainly from the death of Máel Sechnaill in 1022, if not earlier.
Downham, Clare (2007), Viking Kings of Britain and Ireland: The Dynasty of Ívarr to A.D. 1014, Edinburgh: Dunedin, ISBN978-1-903765-89-0
Hudson, Benjamin (2005), Viking Pirates and Christian Princes: Dynasty, Religion, and Empire in the North Atlantic, New York: Oxford University Press, ISBN978-0-19-516237-0
Woolf, Alex (2007), From Pictland to Alba, 789–1070, The New Edinburgh History of Scotland, Edinburgh: Edinburgh University Press, ISBN978-0-7486-1234-5