A: When a Lync client downloads the address book, it stores the content in the GalContacts.db file. With a large address book, you might wish you could pre-populate the address book cache to avoid many clients downloading at the same time, but this pre-population isn’t possible.

However, it shouldn't be necessary anyway. By default, when the Lync client starts, it doesn’t automatically download the address book but rather waits a random interval within 60 minutes of Lync startup.