Hi,
I agree with Andy. An offline address book (OAB) is a copy of an address list collection thats been downloaded so a Microsoft Outlook user can access the address book while
disconnected from the server.
If you are in cached mode and if you are working online (that is, your connection status indicates Connected), Outlook uses both the offline address book and the global address list to provide a complete listing of user information. If you are in cached
mode and if your connection status shows either Disconnected or Offline, you can see only the information that is available in the offline address book.
And the list for All Contacts, All Groups, All Users, All Rooms is the directly accessing for GAL in Exchange server. I think the following KB would provide you a clear understanding about OAB in Outlook:
http://support.microsoft.com/en-us/kb/841273
Regards,