Item Update Session
The UpdateSession service manipulates sessions that are used to upload content into the Content Library Service, and/or to remove files from a library item. An update session is a resource which tracks changes to content. An update session is created with a set of files that are intended to be uploaded to a specific ItemModel, or removed from an item. The session object can be used to track the uploads and inspect the changes that are being made to the item by that upload. It can also serve as a channel to check on the result of the upload, and status messages such as errors and warnings for the upload.
Modifications are not visible to other clients unless the session is completed and all necessary files have been received.
The management of the files within the session is done through the File service.