ORS § 105.020
A defendant who is in actual possession may, for answer, plead that the defendant is in possession only as tenant of another; naming the landlord and the place of residence of the landlord. Thereupon the landlord, if the landlord applies therefor, shall be made defendant in place of the tenant and the action shall proceed in all respects as if originally commenced against the landlord. If the landlord does not apply to be made defendant within the day the tenant is allowed to answer, the landlord shall not be allowed to, but shall be made defendant if the plaintiff requires it. If the landlord is made defendant on motion of the plaintiff the landlord shall be required to appear and answer within 10 days from notice of the pendency of the action and the order making the landlord defendant, or such further notice as the court or judge thereof may prescribe.
ORS 105.020