The Internet Transaction Server (ITS) detects when an unsynchronized situation occurs and notifies the Web transaction.
To handle this notification, your ABAP code should:
Respond to special function codes
Call a function module for information on the SAP system screen that needs to be resynchronized
The ITS notification also tells you whether the update screen is a standlone Dynpro (MAIN) or a subscreen (INCLUDE Dynpro).