Microsoft: Update GAL and OAB in Exchange with PowerShell

The PowerShell scripts below allow you to update your Exchange immediately.

To update the Global Address List (GAL):

Get-GlobalAddressList | Update-GlobalAddressList

To update the Offline Address Book (OAB):

Get-OfflineAddressBook | Update-OfflineAddressBook

When you update the OAB, you’ll also need to update the Client Access Server:

Get-ClientAccessServer | Update-FileDistributionService

Reference:
PowerShell – Howto Update the GAL and OAB in Exchange
http://jeffwouters.nl/index.php/2012/09/powershell-howto-update-the-gal-and-oab-in-exchange/