If You Are Sick
In all cases, notify the Administrative Assistant and the class as soon as possible.
If it's a one-off due to extreme illness: send an email to the class via Class Roster, MyInfo (which ensures that you receive a copy of the email you send, unlike D2L), and contact the Administrative Assistant as early as possible to have a notice put on the door.
If you are unable to fulfill your contract: Contact the Administrative Assistant and Chair as soon as possible. The Chair or Administrative Assistant will work with you to keep you in the loop, and will work with your Union to ensure that the terms of the Agreements are met.