Some one (A Customer) have two branch company worked on one database
over lease line, for now that is good, but he is have problem with
this line, some time it damaged or going shutdown (I am also not
understand why!) so he ask me if there any way to work offline when
the line/network not worked, after going online must make
synchronization and return to online mode (Automatically), he
mentioned Replication, but Replication mean working offline and sync
every period time not switch between Online/Offline

I heard about Shadowing database, what is "Shadow" and what i can do
to resolve his problem.

Thanks