[Session variable] sync_last_received_anchor, sync_new_received_anchor [Usage] 
Used to define the set of changes to be synchronized during a session. During the current synchronization, the command specified for the SelectNewAnchorCommand property provides a new anchor value. Changes that are made after the last received anchor value and before the new received anchor value are synchronized. The new received anchor is then stored and used as the last received anchor value for the next synchronization. For more information, see "Determining Which Data Changes to Download to a Client" in Tracking Changes in the Server Database.