Please arrange your own accomodation, unless you received different information from the organizers as a speaker. There are many hotels and private rooms in Oldenburg, see Accommodation in Oldenburg . Private rooms are usually cheaper, but often without breakfast, look at the list on this page (German only).
There is also a good quality youth hostel in Oldenburg near the city centre. You may contact it via
Tel. 0441 - 87135
Fax: 0441 - 8852493