Sync entire database

We currently use OC 8.0. hosted on an Apache server on our office network. we use is as a 'Client Portal' and set up our clients as users. they login via a link on our website. We use the database to store the client documents and access it like any other windows folder.
This has worked well for the last 18 months or so but has started causing some issues lately, So we have just installed OC 9.1.4 on our web space with Go-daddy.

We still need to keep our client data local (on our network), is it possible to use the windows desktop client to sync all of the user files on our network with the OC Database in our web-space?

we have approximately 300 users, although not all of them are actively accessing their accounts

I don't see the problem. You have ownCloud, you have your Desktop Client and the Database.

Why would you not be able to sync it?