As a contracted KPSU DJ, you are legally required to fill the time slot you are assigned. Nearly all times slots are at least a two hour a week time commitment: one hour before you go on the air, and one hour during your broadcast. Additional time might be necessary to help clean up after your broadcast, or before to help prepare for a particularly unusual show (conducting interviews, hosting live performances, etc).
In the event that you cannot make it to your show, you are still responsible for finding a replacement to fill the time. The primary means for finding a replacement is posting a message on the KPSU volunteer mailing list at the following address: KPSU-DJs@lists.pdx.edu. If someone writes you back offering to cover the show, you either forward the information to the Programming Director, or let the PD know who has agreed to cover your show. You will probably need to follow up with the DJ to make sure they understand their responsibilities, or any peculiarities that your show entails. If you had solicited the need for a sub on the KPSU email list serv, you must then announce that you've found a sub to prevent further confusion and/or emails from others wanting to sub for you.
Seeking out a sub for your show should be done with at least one week notice. If for some reason you are unable to find a sub, you MUST alert the Program Director of such. Failure to do so is grounds for a strike and may be considered a "no call, no show." Consider, that if you require multiple replacements on a regular basis, your slot will be reassigned until you can become a more consistent announcer.
A DJ may also pre-record their show and arrange with another DJ (most likely the DJ preceding your show) to play your pre-recorded show. Your pre-record should include the required legal IDs, PSAs, and Promos mixed in, but if they aren't, alert the DJ agreeing to start your show that they first need to satisfy these requirements.