If students are already enrolled in another section of the class for which they want to waitlist, SWAP should be used. If students use the ADD enrollment feature to get on a waitlist for a different section of the same class, they must DROP the section in which they are enrolled before they will be moved from the waitlist.
Students may also want to use SWAP if there is a known time conflict between an already enrolled class section, and the section for which they want to waitlist. If students get on a waitlist using the ADD enrollment feature, they will not be auto-enrolled into the waitlisted class until they DROP the class that presents the time conflict or the class.
Finally, students may want to use SWAP if they are already enrolled in the maximum number of units for a term and want to still get on a waitlist. If a student gets on a waitlist using the ADD enrollment feature, they will not be auto-enrolled into the waitlisted class until they DROP a class that would allow the waitlisted class to fall within the maximum number of allowable units to be enrolled in for a term.
SWAP should not be used to attempt to get on a waitlist for a closed lab or recitation, if students are already enrolled in the lecture associated with that closed lab or recitation. Students will be dropped from their enrolled class and placed on the waitlist for the lecture until a seat opens in the closed lab/recitation, since students cannot be enrolled in a lecture section and waitlisted for that same lecture simultaneously.