Microsoft Office Outlook 2003 introduced Cached Exchange Mode as the default e-mail profile. However, Outlook 2003 does not maintain a persistent connection to a global catalog server. This connection behavior affects the look up of e-mail addresses and the name resolution functionality in Outlook 2003 in Cached Exchange Mode. Therefore, Outlook 2003 in Cached Exchange Mode uses the Offline Address Book to look up e-mail addresses and for name resolution.
Issues that you experience when you run Outlook 2003 in Cached Exchange Mode
If you use Outlook 2003 in Cached Exchange Mode with an online store and a local Offline Address Book, network traffic to the Microsoft Exchange Server and to global catalog servers is significantly reduced.
However, the advantages of running Outlook 2003 in Cached Exchange Mode also presented some new issues for Exchange Server and for Active Directory administrators before the release of Exchange Server 2003 SP2.
The following is a list of some of the issues that you experience when you ran Outlook 2003 in Cached Exchange Mode before the release of Exchange Server 2003 SP2:
- Unexpected full Offline Address Book downloads - You perform an Offline Address Book download for one client. However, a full Offline Address Book download on every Outlook 2003 in Cached Exchange Mode client in the Exchange Server organization occurred. This behavior uses a significant amount of network bandwidth in some environments.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
839826
High network usage occurs while Outlook clients download the offline Address Book from Exchange 2003 at the same time
- Sort locale mismatch - You want to consolidate the remote servers from remote sites to a single server that is in a central site. Before the release of Exchange Server 2003 SP2, this process required that you build both browse and name resolution indexes on the server that has a single locale. Therefore, all remote sites end up having the Offline Address Book with the same sort locale.
- Name resolution fails - You want to use the first name of a contact to locate them in the Offline Address Book. However, the display names are set in the "LastName, FirstName" format in the Offline Address Book. If the Offline Address Book files do not have the firstname attribute indexed, you cannot use the first name of a contact to locate them in the Offline Address Book.
Configuration
The following is a list of the configuration limitations of Offline Address Book version 4:
- If you upgrade to Exchange Server 2003 SP2, the server will generate the new Offline Address Book version 4 files. However, if you have not installed Outlook 2003 SP2 on the client computers, Outlook 2003 cannot locate the Offline Address Book version 4 files. Therefore, Outlook 2003 continues to download the earlier versions of Offline Address Book files.
- If you upgrade to Outlook 2003 SP2 while you continue to use versions of Microsoft Exchange Server that are earlier than Exchange 2003 SP2, the clients will continue to download the earlier versions of Offline Address Book files.
Changes to the server-side architecture
The underlying server-side architecture of the Offline Address Book generation process is not changed with Offline Address Book version 4. The OABGen process continues to generate the Offline Address Book files. Additionally, the OABGen process continues to be posted to a public folder by using the same hierarchy as the versions of the Offline Address Book that are earlier than Offline Address Book version 4.
However, the following server-side architecture changes do occur in Offline Address Book version 4:
- The Offline Address Book files are located in a folder that is named OAB Version 4.
- Full Offline Address Book posts use a new file that is named the Data.oab file. The Data.oab file contains all the Offline Address Book recipient data.
- A full Offline Address Book is not added to the public folder if the generation of the differential Offline Address Book fails for any reason. This behavior minimizes the chances of clients unintentionally downloading a full Offline Address Book.
Additionally, this behavior occurs in Offline Address Book version 4 and earlier versions of Offline Address Book. Therefore, you do not have to have Outlook 2003 SP2 installed. However, you must have Exchange Server 2003 SP2 installed because it is the program that generates the Offline Address Book files. - Offline Address Book updates (full or differential) are not generated if there are no changes that are required in a differential update. Exchange Server will update properties of the existing Offline Address Book files. Exchange Server does this so that the Offline Address Book files do not expire prematurely.
However, Exchange Server will not update the sequence number of the Offline Address Book. Therefore, Microsoft Outlook clients do not download any Offline Address Book files if the client sequence number matches the server sequence number. - Addition or removal of Parent Distinguished Names (PDNs) in Active Directory directory services no longer causes full Offline Address Book downloads.
- If there is a template change on the server, Exchange Server will include the new template in a differential Offline Address Book instead of the full Offline Address Book. This behavior is possible because the client builds the Offline Address Book indexes.
- Differential Offline Address Book posts use a new file that is named the Binpatch.oab file. The Binpatch.oab file will contain the incremental changes from the previous day.
- Both the Data.oab and the Binpatch.oab files use BinPatch (Binary Delta Compression) technology. This is the same technology that is used by Microsoft Windows Server Update Services (WSUS) to download new software updates to workstations and to servers. This new process allows for the full Offline Address Book size to be reduced by approximately 35 percent (%).
BinPatch takes two binary files that have lots of similarities, and then it produces another highly compressed file named the �patch file�). This patch file can be used to convert the original file to the new one. In the Offline Address Book, the BinPatch process generates a compressed file that can be applied to the original Offline Address Book file.
This process produces the new, updated Offline Address Book file. Because the data in the patch file is not based on the structure of the data in each data file, the resulting Offline Address Book files exactly match the Offline Address Book files that you would generate with a full Offline Address Book download.
Changes to the client-side architecture
The client-side architecture does not change much after you install Outlook 2003 SP2. The following client-side architecture changes do occur in Offline Address Book version 4:
- Outlook 2003 will perform a full Offline Address Book download by downloading the Data.oab file from the server after the initial installation of Offline Address Book version 4. After that, Outlook 2003 only downloads one or more of the Binpatch.oab files from the Exchange Server server.
The number of Binpatch.oab files that are downloaded is a function of the sequence number that is stored on the Outlook client. The highest sequence number of the Offline Address Book files is stored on the server.
Note If your Outlook 2003 profile is currently in non-Unicode mode, you are using Offline Address Book version 2. In this scenario, your Outlook client is not automatically upgraded to Offline Address Book version 4. If you want to upgrade to Offline Address Book version 4, you must create a new Outlook profile. The new Outlook profile should automatically be in a Unicode mode profile. By default, this new Outlook profile will download Offline Address Book version 4 if it is available. - Because Outlook 20003 automatically downloads Offline Address Book version 4 as soon as it is available on the Exchange Server, you must consider staggering your Outlook 2003 SP2 deployment.
If you do not stagger your Outlook 2003 SP2 deployment, you may affect the network in a negative way because of the number of full Offline Address Book version 4 downloads that will occur at the same time.
If staggering the Outlook 2003 SP2 update is not an option, you can also use the Offline Address Book throttling mechanism that is available in Exchange Server .
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
867623
Throttling full offline Address Book downloads to limit the effect on a LAN in Exchange Server 2003
- For an Outlook client to update its Offline Address Book, the client must download all the Binpatch.oab files from the server to upgrade to the latest version. After this process is complete, the client applies these Binpatch files to the Data.oab file. The end-result is the same as if you had downloaded the full Offline Address Book.
- Before the release of Offline Address Book version 4, Outlook 2003 used a default threshold of 1/8 to determine when the program should perform a differential Offline Address Book download or a full Offline Address Book download.
If you are using Outlook 2003 SP2 and Offline Address Book version 4, this threshold has been increased to 50 percent. Outlook 2003 calculates a percentage ratio of the total size of all the compressed differential Offline Address Book files on the server to the current total size of the compressed full Offline Address Book on the server. If the percentage ratio exceeds the threshold value, Outlook 2003 performs a full download instead of a differential download. - Offline Address Book browse and ambiguous name resolution (ANR) indexing will be based on the locale language and country settings of the client and not on the server. With Offline Address Book version 4, the client generates the locale specific indexes for the Offline Address Book version 4 Data.oab file regardless of what locales are on the server.
- Because the client is now responsible for generating the Offline Address Book indexes, there may be a small increase in the time that is required for the complete Offline Address Book download+extraction cycle.
- Memory requirements for the Offline Address Book are higher than they were for earlier versions of the Offline Address Book. If Outlook 2003 detects an issue that occurs because of low memory, the program will automatically modify the download mechanism so that the memory requirements for index generation are optimized.
- Even though you can select a no details Offline Address Book download in Outlook 2003, you will always receive a full details download. The Offline Address Book version 4 architecture does not support a no details download. This behavior may increase the local Offline Address Book data if you are currently using a no details Offline Address Book download on your clients.
Administration
There are several new registry values that you can use to configure or to control Offline Address Book version 4 downloads. Before you use any one of these registry settings in a production environment, you should thoroughly test them in a lab environment.
Restricting access to earlier versions of the Offline Address Book
By default, Outlook 2003 will look for Offline Address Book version 4 on the Exchange Server after you install Outlook 2003 SP2. If Outlook 2003 finds Offline Address Book version 4, the program will download that version of Offline Address Book. This behavior occurs regardless of the version of the Offline Address Book that Outlook 2003 was using the day before. However, if Outlook 2003 cannot locate Offline Address Book version 4 on the Exchange Server, the program will fallback to the highest version of the Offline Address Book that it finds on the Exchange Server.
Registry information
Use the following registry information to keep Outlook 2003 clients from falling back to an earlier version Offline Address Book
If you do not want your Outlook 2003 clients to fallback to an earlier version Offline Address Book, add the registry data to one of the following registry subkeys.
Use this registry subkey if you are applying a registry policy (GPO)HKEY_CURRENT_USER\Software\Policies\Microsoft\Exchange\Exchange Provider
OAB v4 Only
Use this registry subkey if you are not applying a registry policy (GPO)
HKEY_CURRENT_USER\Software\Microsoft\Exchange\Exchange Provider
:OAB v4 Only
Values:
- 0: This is the default registry value. Microsoft Outlook performs the same fallback logic as it does today for Unicode mode if you use this value. Outlook will try to get the latest version of the Offline Address Book that is available currently on the server. Additionally, this value means that no registry key is present or is used for any other value than a value of 1.
- 1:
Outlook will only use Offline Address Book version 4 when you use this value. This behavior occurs regardless of what other Offline Address Book versions are present on the server. If Offline Address Book version 4 is not present on the server when you use this value setting, Outlook will not use an Offline Address Book. Instead, Outlook uses the online version of the global address list.
Use the following registry information to control the threshold at which a differential update is not used
The following registry data determines whether Outlook 2003 performs a full download or a differential download of the Offline Address Book.
Use this registry subkey if you are applying a registry policy (GPO)HKEY_CURRENT_USER\Software\Policies\Microsoft\Exchange\Exchange Provider
HKEY_CURRENT_USER\Software\Microsoft\Exchange\Exchange Provider
: OAB v4 Full Download Threshold
Values:
The value number is in hexadecimal between 1 and 64. This behavior is interpreted as a percentage value. Note, 64 hexadecimal = 100 decimal.
Outlook 2003 calculates a percentage ratio of the total size of all the compressed differential files on the server to the current total size of the compressed full Offline Address Book on the server. If the percentage ratio exceeds the threshold value, Outlook performs a full download instead of a differential download.
Registry information to use the Random Retry timer (Full downloads only for Offline Address Book versions 2, 3a, and 4)
Outlook 2003 SP2 introduces a new registry policy setting. This new registry policy setting lets you disperse full Offline Address Book download requests to randomly start between 1 hour and a specified number of hours.
If the registry policy is set [GM1] [GM1] and a full Offline Address Book download is required, Outlook 2003 performs the full Offline Address Book download in a random time between 1 hour and the number of hours that you specify in the registry.
Use this registry subkey if you are applying a registry policy (GPO)
HKEY_CURRENT_USER\Software\Policies\Microsoft\Exchange\Exchange Provider
HKEY_CURRENT_USER\Software\Microsoft\Exchange\Exchange Provider
: Max Full OAB Download Wait
Values: Integer value >= 1
Note The registry settings only apply if Outlook already has a usable Offline Address Book. If Outlook does not have a usable Offline Address Book, the registry settings are ignored until you have a usable Offline Address Book.