The Offline Address Book (Part 3)

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So far in the article series on the web-based distribution method of the Offline Address Book (OAB) in Exchange 2010, we have covered how the OAB data is first generated on the mailbox server and taken the time to look at where the data is actually created and stored. We then moved on to look at the diagnostics logging process for this data as this forms an important part of the overall troubleshooting process.

We will now continue this article series by looking at the actual web-based distribution model.

Web-Based Distribution

Although the OAB files in the lab are generated on the mailbox server LABMBX, they still need to be distributed to the client machines. Since the client machines do not connect to the mailbox server to download the OAB when considering web-based distribution, clearly another process is involved. With this in mind, let’s look closer at the web-based distribution method for distributing the OAB, which is performed by the Client Access Server role. In the lab environment the Client Access Server role is running on a separate server named LABCAHT, which is also running the Hub Transport server role. In Figure 4 in part one of this article, it can be seen that the web-based distribution point is configured as the virtual directory named OAB (Default Web Site) on the server called LABCAHT. On the Client Access Server role, a new virtual directory called OAB that runs within the Default Web Site is available to support the OAB files. This can be seen in the Internet Information Services Manager snap-in running on the Client Access Server LABCAHT, as shown in Figure 11.

Figure 11: OAB Virtual Directory

By right-clicking the OAB virtual directory and choosing the explore option from the context menu, Explorer opens to reveal the location of the folder that contains the OAB files on the Client Access Server. This location is \Program Files\Microsoft\Exchange Sever\V14\ClientAccess\OAB as shown in Figure 12.

Figure 12: Client Access Server OAB Folder

As you can see from Figure 12, the sub-folder under the OAB folder has the same GUID name as the corresponding folder on the mailbox server which you saw in Figure 6 in part two of this article. Additionally, you can also see that the actual files within the GUID folder have the same names as those found in the corresponding GUID folder also seen in Figure 6 of this article. In other words, the OAB files are synchronized between the mailbox server that generates them and the Client Access Server that distributes them in the web-based distribution method. Earlier in this article I mentioned how it was important to ensure that file-level antivirus exclusions were in place for the sub-folders of the ExchangeOAB folder on mailbox servers. The same rule applies for the sub-folders of the OAB folder on the Client Access Server role. Take the time to ensure that this configuration element is in place.

The next piece of the puzzle is to understand how the files are copied from the mailbox server role to the Client Access Server role. This process is performed by the Microsoft Exchange File Distribution Service that runs on the Client Access Server. In fact, the Microsoft Exchange File Distribution Service also updates Unified Messaging and Group Metrics data, but for this article we’re only concerned with the OAB data that it updates.

When the Microsoft Exchange File Distribution Service first starts, it polls for OAB data and copies the data from the mailbox server to the Client Access Server. Thereafter, the service will poll for OAB data every 8 hours. This 8 hour interval is actually configured as a parameter on the properties of the OAB virtual directory. Consider Figure 13 where the full properties of the OAB (Default Web Site) virtual directory have been listed. The parameter of interest is highlighted, namely PollInterval. You can see that this parameter has a value of 480, which represents 480 minutes or 8 hours.

Figure 13: OAB Virtual Directory Properties

You could consider changing the PollInterval setting on the virtual directory if you had the situation where the OAB generation process was occurring on a greater frequency than the once-per-day default and you needed to ensure that new address book additions were automatically available to Outlook in a timely manner. However, 8 hours for the poll interval is likely to be a good setting in many Exchange deployments so consider the impact on your servers before changing this.

Having said this, there are two ways to force a manual poll. Re-starting the Microsoft Exchange File Distribution Service is one way to force a poll for new OAB data but of course this isn’t really a practical solution within a production environment. Fortunately, the Update-FileDistributionService cmdlet can be used to perform this function and is therefore a useful cmdlet to know for those occasions where you need to quickly ensure that a new mailbox will be visible in the OAB.

The Microsoft Exchange File Distribution Service can actually check for three different types of data, namely OAB, Unified Messaging and Group Metrics data. As a result, a cmdlet parameter called Type is available to allow you to choose which data you wish to update. This cmdlet parameter should have a value of OAB when considering OAB updates. However, the Type parameter is optional and if omitted all three types of data supported by the service are updated. To manually update the Microsoft Exchange File Distribution Service for the OAB service on the Client Access Server named LABCAHT, the following cmdlet can be used:

Update-FileDistributionService –Identity LABCAHT –Type OAB

Running this cmdlet doesn’t produce any screen output as such, but you may briefly see the status messages such as the one shown in Figure 14.

Figure 14: Updating The File Distribution Service

File Distribution Service Diagnostics Logging

Since the Update-FileDistributionService cmdlet doesn’t produce any screen output, it can be helpful to examine the event log to see details of the Microsoft Exchange File Distribution Service process. First, though, it’s necessary to increase the diagnostics logging level for this service in the same way that we did for the MSExchangeSA service earlier in this article series. Using the Exchange Management Console, remember to first select the relevant Client Access Server and then select the Manage Diagnostics Logging Properties… option from the action pane. In the Manage Diagnostics Logging Properties wizard scroll down until you find the MSExchangeFDS entry, which represents the Microsoft Exchange File Distribution Service. Expand this entry and set both the FileReplication and General categories to a level of High as you can see from Figure 15.

Figure 15: Setting Diagnostics Logging Levels Using Exchange Management Console


We’ll continue looking at the diagnostics logging properties for the File Distribution Process in the fourth and final part of this article series, including sample event log entries that you should watch for. Also in the last part of this article series, we’ll look at how the Outlook client actually downloads the OAB data and also the final configuration elements that allow this Outlook download process to take place.

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