The default Office Communication Server (OCS) configuration resynchronizes the address book at 1:30AM local time each day. By default the Microsoft Office Communicator (MOC) client looks for changes in the address book files on a random interval (between 0 and 60 minutes) upon start-up or within 24 hours when running.
To force an immediate update:
Delete the GalContacts.db and GalContacts.db.idx files from the relevant SIP user in folder
%userprofile%\Local Settings\Application Data\Microsoft\Communicator
To set the GalDownloadInitialDelay registry entry for immediate download of the GAL file follow these steps:
Locate the registry subkey HKEY_CURRENT_USER\Software\Policies\Microsoft\Communicator
Create a new DWORD Value called GalDownloadInitialDelay and set its Value to 0
Setting the value to 0 will allow the address book download to take effect immediately upon sign-in after starting or re-starting MOC. Without the value set MOC uses a random value between 0 and 60 minutes.