How to configure how the Offline Address Book is downloaded when you use Outlook in Cached Exchange Mode

This article describes how to configure how the Offline Address Book is downloaded when you use Microsoft Office Outlook 2007 or Microsoft Office Outlook 2003 in Cached Exchange Mode.

To configure how the Offline Address Book is downloaded when you use Outlook in Cached Exchange Mode, follow these steps to configure the DownloadOAB value in the Registry.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate and then click to select the following key:
   
   Outlook 2003
   HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook
   Outlook 2007
   HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook
4. On the Edit menu, point to New, and then click Key.
5. Type Cached Mode.
6. On the Edit menu, point to New, and then click DWORD Value.
7. Type DownloadOAB, and then click OK.
8. In the right pane, right-click DownloadOAB, and then click Modify.
9. In the Edit DWORD Value dialog box, type the value that you want, and then click OK.
10. On the Registry menu, click Exit.

You can set the DownloadOAB value to any one of the following values, depending on your situation:

• 0 = The Offline Address Book does not download automatically.
• 1 = The Offline Address Book uses the Download Full Items download mode. This is the default setting.
• 2 = Download the Offline Address Book in any download mode, but download a differential update in the Header only download mode.
• 3 = Always download the Offline Address Book and a differential update in one of the following download modes:
  • Download Headers and then Full Items
  • Download Full Items
  • Download Headers

Note If Offline Address Book (.oab) files were previously downloaded and associated with a MAPI profile for Microsoft Outlook, this setting will not have the correct effect. To use this setting, you must set the registry value, remove any .oab files from the local computer, and then synchronize.

When you set this registry value to 0 (zero), cached-mode Outlook is forced to perform directory lookups against an Active Directory directory service global catalog server. This action increases the timeliness of access to modified or new Active Directory objects. However, this action also negates some of the increased tolerance for network latencies and outages.