The idea of disconnected operation is central to Coda, and was part of its design from the beginning; the earliest Coda papers speak of `mobile computing'. A client may lose contact with the cell's servers accidentally, whether through network failure or because servers go down, or deliberately, because you are removing the client, or because networking over a phone line is too expensive to do continuously.
Besides files that may happen to be in the cache, Coda lets you select portions of the file system which the cache manager tries (if possible) to `hoard'; that is, to keep current. You can set priorities to guide the cache manager in this. Reconnecting is easy if you haven't changed anything. If you have, if you created or edited files while the system was disconnected, you need to tell the system to reintegrate your changes.
Of course, it is possible while your system is disconnected, for two people to change the same file or directory independently. In that case, Coda provides a mechanism for comparing the different versions, harmonising them, and resolving the conflict.