I have an application that also has a web interface, one of the requirements is to be able to work on the application even if there isn't an internet connection available.
Is there a need to sync between those databases?
Those databases are ought to be pretty big disk space wise.
If there is such a need how should it be done? What database should I use?
The target OS is windows but the server could run on windows or linux.<
Do you mean you need to be able to work via the web application even when offline? Sounds like you need Google Gears or another HTML5 structured storage implementation.
If you using a native app when offline, then yes, it sounds like you'll want a local database for that too.
Do the users typically know when they're going to go offline? If so, you could let them "check out" the subset of the database they're going to need, then later "go online" and synchronize. Otherwise, you may want to synchronize data that they've used recently, but purge the local database of data they haven't used for a long time.
Quite how hard that will be will depend on your exact application. Do multiple users need to be able to work on the same set of records simultaneously, for example?
来源：https://stackoverflow.com/questions/1085677/syncing-between-two-databases