Oregon Revised Statutes Domestic Relations § 108.120

(1) After the hearing of the petition for an order of support the court shall make an order granting or denying it and fixing, if allowed, the terms and amount of the support.

(2) The court has the same power to compel the attendance of witnesses or the production of testimony as in actions and suits, to make such judgment or orders as are equitable in view of the circumstances of both parties and to punish violations thereof as other contempts are punished.

(3) The judgment or order is final as to any installment or payment of money that has accrued up to the time the nonmoving party, other than the state, is served with a motion to set aside, alter or modify the judgment or order. The court may not set aside, alter or modify any portion of the judgment or order that provides for any payment of money, either for minor children or for the support of a party, that has accrued before the motion is served. However, the court may allow a credit against child support arrearages for periods of time, excluding reasonable parenting time unless otherwise provided by order or judgment, during which the obligor, with the knowledge and consent of the obligee or pursuant to court order, has physical custody of the child.