Microsoft KB Archive/269439

= XADM: Synchronization of .ost Files Does Not Work When the Antivirus API Is Enabled =

Article ID: 269439

Article Last Modified on 10/26/2006

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APPLIES TO


 * Microsoft Exchange Server 5.5 Service Pack 3

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This article was previously published under Q269439



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
If Exchange clients attempt to synchronize the .ost files when third-party software that uses the new antivirus application programming interface (API) is installed on the Exchange Server computer, the clients may experience slow synchronization, synchronization time-outs, or inability to complete the synchronization process.



CAUSE
This issue can occur because when the antivirus API is in use, each message that contains an attachment must be scanned before the message is released to a client by the Exchange Server information store. If the scanning queue contains messages that contain many attachments or several large attachments, the client may time out while it waits for the server to release the message that contains the attachment.



RESOLUTION
To determine whether you are experiencing the issue that is described in this article, disable the antivirus API by either disabling the third-party software or changing the Enable value in the registry. To change the Enable value, you need to edit the registry:

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

WARNING: When you disable the antivirus API and subsequently re-enable the antivirus API, all attachments are resubmitted to the third-party software to be scanned.  Start Registry Editor (Regedt32.exe). Locate the Enabled value under the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\VirusScan

 On the Edit menu, click DWORD, type 0, and then click OK. Quit Registry Editor.

After you change the Enabled value, allow up to two minutes for the change to take effect, and then test .ost synchronization.

If .ost synchronization finishes normally, re-enabled the antivirus API by changing the Enabled value back to 1.

Although the performance of the antivirus API is bound by the third-party software implementation, you can add or change the OpenRetryDelay value in the registry to try to resolve this issue. This value is the time interval in milliseconds that the information store pauses before it attempts to reopen attachments that are currently being scanned when those attachments are requested by the client. If you set this value too high, you may cause client time-outs, and if you set this value too low, you may cause additional processing overhead by the information store. If this value is not present in the registry when the antivirus API is in use, it has a hard-coded default value of 500 milliseconds.

IMPORTANT: Although the following procedure uses a value of 250 milliseconds, this value may not be the correct value in every case. Choose this value based upon your particular environment.  Start Registry Editor (Regedt32.exe).</li> Locate the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\VirusScan

If the VirusScan key is not present, the antivirus API is not in use or has never been enabled on the Exchange Server computer.

</li> Locate the OpenRetryDelay value under the preceding key in the registry. If the OpenRetryDelay value is not present, go directly to step 5.</li> On the Edit menu, click DWORD, type 250, select a Radix of Decimal, and then click OK.</li> If the OpenRetryDelay value is not present, add it; on the Edit menu, click Add Value, and then add the following registry value:

Value Name: OpenRetryDelay

Data Type: REG_DWORD

Radix: Decimal

Value: 250

</li> Quit Registry Editor.</li> Restart the information store service to make the changes take effect.</li></ol>

If you do not notice any improvement after you change this value, contact the third-party software representative for assistance in further improving performance of the antivirus scanning process.

Additional query words: Anti-Virus AVAPI Sync timeout vapi

Keywords: kbprb KB269439

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