'O God' in the Bible

I give you praise and worship, O God of my fathers, who have given me wisdom and strength, and have now made clear to me what we were requesting from you: for you have given us knowledge of the king's business.

But you have been lifting yourself up against the Lord of heaven, and they have put the vessels of his house before you, and you and your lords, your wives and your women, have taken wine in them; and you have given praise to gods of silver and gold, of brass and iron and wood and stone, who are without the power of seeing or hearing, and without knowledge: and to the God in whose hand your breath is, and whose are all your ways, you have not given glory;

Then they made answer and said before the king, Daniel, one of the prisoners of Judah, has no respect for you, O King, or for the order signed by you, but three times a day he makes his prayer to God.