Recipe5.25.Creating and Using Offline Address Lists

Recipe 5.25. Creating and Using Offline Address Lists

Problem

You want to control the offline address lists (OALs) on your server.

Solution

Using a graphical user interface

To set the properties of an OAL, do the following:

1. Open the Exchange System Manager (Exchange System Manager.msc).

2. Expand the Recipients node and select the Offline Address Lists node.

3. Right-click the OAL you want to modify and choose the Properties command.

4. Choose the server you want to be responsible for generating the OAL by clicking the Browse button. This can be any server in any administrative group.

5. Use the Address lists field and the Add and Remove buttons to include or exclude the global address lists you want included in your OAL. By default, your organization will have a single OAL that will contain the default GAL.

6. Use the Update interval drop-down listing and the Customize button to schedule when you want the OAL generated. Microsoft recommends that you leave this interval set to no more than once per day, unless your server resources allow more frequent updates. The time required to build the OAL increases as the number of accounts in the included address lists increases. However, Outlook 2003 users in cached Exchange mode won't see account additions and deletions until the next time they download an up-to-date OAL.

7. Click OK.

To create a new OAL, do the following:

1. Log on to your Exchange server using an account that has administrative privileges on the domain.

2. Open the Exchange System Manager.

3. Expand the Recipients node and right-click the Offline Address Lists node.

4. Choose the New Offline Address List command.

5. Give the new OAL a name, then use the Browse button to select the server you want to generate the OAL. Click Next.

6. Select the address lists you want included in the OAL, then click Next.

7. Click Next again to acknowledge that the new OAL won't be created until the next scheduled window for store maintenance, then click Finish.

Discussion

Before we start in on the details of how offline address lists work, let's straighten out a terminology wrinkle. The Outlook team calls these objects "offline address books," or OABs. The Exchange team sometimes calls the same things OALs, but sometimes they call them OABs. Don't let this confuse you too much.

OALs are designed as a convenience for clientsspecifically, clients that may not be connected to the server at a given time. The idea behind the OAL is that it should serve as a locally available replica of selected address lists that can be used for address resolution on a machine that cannot connect to an Exchange server at the time. If you think of the OAL as merely an offline version of the GAL (or of selected GALs, since you can choose which specific address lists are included in a particular OAL), you've got the idea, although the OAL doesn't include all of the information found in the GAL (custom properties and group membership data isn't included). Outlook uses its local copy of the OAL to handle both GAL browsing and name resolution when offline.

The OAL itself is a set of .OAB files that are stored in a system public folder, the name of which varies according to the version of Exchange you're using (for Exchange Server 2003, it's OAB Version 3a); that's why, when you create a new OAL, you have to wait for store maintenance to runa new instance of the system public folder has to be created. Each day, the Exchange system attendant kicks off a process known as OABGen; it creates an incremental file (changes.oab) that contains all the changes made in the preceding 24 hours. This daily incremental update is posted to the folder so that clients can download it; by default, the folder's aging limit is set to 30 days, so clients can pull up to 30 days of deltas before they have to download a complete OAL. Speaking of complete OALs: after the daily differential object is created, OABGen refreshes the full copy of the OAL and stores it as well.

There are several circumstances in which Outlook will download a full OAL:

• When Outlook connects to the server for the first time, it will download the full version of the OAL. After that, it will download the next day's incremental after 24 hours have elapsed, and every 24 hours after that.

• If Outlook has an older version of the OAL and it connects to a server that only has a newer version, it will download the newer version. For example, if you move a user's mailbox from an Exchange 5.5 to an Exchange Server 2003 server, the old OAL will be an old version, so it'll be replaced.

• If the total volume of incremental changes needed to bring the OAL up to date is more than one-eighth the total size of the full OAL, Outlook will just go ahead and download the whole thingthis keeps it from downloading updates that have been superseded by other later updates. MS KB 841273 describes a number of tweakable parameters that control Outlook's behavior in this regard. This kind of mass change can happen if you change or add recipient policies or modify some AD schema objects.

• If you create or remove an administrative group, Outlook has to fetch the full OAL because the Exchange parent distinguished name (PDN) table has changed.

• If there's a missing incremental file, Outlook has to fetch the full OAL because it can't recover from the missing file. This can occur because of a problem on the server, or because Outlook has been offline for longer than the aging period on the OAL's public folder.

• When you tell it to by using the Tools Send/Receive Download Address Book command.

See Also

Recipe 5.12 for creating address lists, MS KB 841273 (Administering the Offline Address Book in Outlook 2003), and MS KB 811870 (XADM: Troubleshoot offline address book download issues)