Move Mailbox functionality promotes contents of .stm files (329067)


The information in this article applies to:

  • Microsoft Exchange Server 2003 Enterprise Edition
  • Microsoft Exchange Server 2003 Standard Edition
  • Microsoft Exchange 2000 Server
This article was previously published under Q329067
Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry

SUMMARY

Microsoft Exchange 2000 Server and Microsoft Exchange Server 2003 Internet protocol (IP) client computers that are using Internet Message Access Protocol 4 (IMAP4), Post Office Protocol 3 (POP3), and WebDAV-based clients, such as Microsoft Entourage 2004, fully use the streaming store (.stm) file to read and write data. If you use the Move Mailbox functionality in Active Directory Users and Computers to move data, the data is promoted into the .edb file. Therefore, clients that use POP3, IMAP4, and WebDAV to access their mailboxes may experience performance issues after you move their mailboxes between databases or servers. For clients that use POP3 or IMAP, after the user logs on, message sizes must be calculated and MAPI-to-MIME conversion occurs in memory and on the disk of the server. For clients that use WebDAV, the client performance issue is seen during a full re-synchronization of a mailbox. For example, this may occur in Microsoft Entourage 2004. In extreme cases, very large temporary files may be created on the Exchange server when this behavior occurs in POP3, IMAP4, or WebDAV scenarios.

MORE INFORMATION

If you are moving hundreds or thousands of mailboxes, you can use either of the following methods to prevent performance issues from occurring:
  • Make sure that the TMP/TEMP environment variables point to a very fast RAID 0+1 spindle set (up to 12 disks for large mailbox servers). For standalone mailbox servers, Microsoft recommends that you adjust the system environment TMP/TEMP variables. For server clusters, Microsoft recommends that you configure the variables for the service account under which the server cluster is running.
  • Add the Compatibility registry value, which informs the store to use approximate instead of exact calculations for message sizes. The following sections describe this procedure in more detail.

Add the Compatibility registry value for POP3 users

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

The Compatibility registry value for POP3 users limits the size of messages that can be converted from MAPI to MIME format. The registry value does this when an Entourage user accesses a folder in the Moved mailbox. This process prevents large messages from being automatically converted when a folder is accessed by the user. Therefore, the effect on performance that occurs when a large message is converted is reduced.

Users who have messages that are larger than the limit that is set in the value can be helped by using this registry subkey. Users who do not have messages that are larger than the set limit will not notice improvement in performance.

For example, when you set the value to 200 MB, messages that are larger than 200 MB are not automatically converted from MAPI to MIME format when an Entourage user accesses a folder in the Moved mailbox. Messages that are larger than 200MB are converted when the user accessed that specific message in a folder.

Because large files are converted when they are accessed, the effect on performance is spread over time. Eventually, all the content of Moved Entourage mailboxes are converted to MIME content (.stm) as the files are accessed.

Note When a user tries to work with a message that is larger than the set value, the user's computer performance may be affected. Additionally, an oversized message may cause performance issues on the server side. This may affect other users.
  1. Start Registry Editor.
  2. Locate and then click the following key in the registry:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\ POP3svc\Parameters

  3. On the Edit menu, click Add Value, and then add the following registry value:

    Value name: Compatibility
    Data type: REG_DWORD
    Radix: Hexadecimal
    Value data: 0xfffffffe

  4. Exit Registry Editor.

Add the Compatibility registry value for IMAP4 users

  1. Start Registry Editor.
  2. Locate and then click the following key in the registry:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\ IMAP4svc\Parameters

  3. On the Edit menu, click Add Value, and then add the following registry value:

    Value name: Compatibility
    Data type: REG_DWORD
    Radix: Hexadecimal
    Value data: 0xfffffffe

  4. Exit Registry Editor.
For more information about this issue, click the following article number to view the article in the Microsoft Knowledge Base:

317722 Client latencies occur when Exchange 2000 converts mail from MAPI to MIME format

Add the Compatibility registry value for WebDAV clients such as Entourage

Add this registry key to at least those Exchange 2003 front-end and back-end servers that Entourage users use to connect to their Exchange mailboxes.
  1. Start Registry Editor.
  2. Locate and then click the following key in the registry:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeWEB\DAV

    Note By default, the DAV key is not in the registry. You will have to create it yourself.
  3. On the Edit menu, click Add Value, and then add the following registry value:

    Value name: MaximumResponseSizeInBytes
    Data type: REG_DWORD
    Radix: Decimal
    Value data: value

    Note To calculate a value for the Value data field, determine the size of the largest message that you want the users to be able to send and receive. For example, if you decide to limit message size to 50 megabytes (MB) and under, you would use the following calculation:

    1024 * 1024 * 50 = 52428800 (Decimal) = 3200000 (Hexadecimal)

    Enter the results of this calculation in the Value data field. In this example, you would enter 52428800 (Decimal) or 3200000 (Hexadecimal). Remember that the configurable range for this registry key is 1 MB to 1 gigabyte (GB).
  4. Exit Registry Editor.
To put this registry key into effect under Internet Information Services (IIS), restart the Exchange Application Pool. Then, if an Entourage user tries to work with a message that is larger than the value in the Value data field, the user may experience performance issues. An oversize message may also cause performance issues on the server side. This may affect other users.

Note This registry key only works for Exchange Server 2003. It does not work for Exchange 2000 Server.
Modification Type:MajorLast Reviewed:7/24/2006
Keywords:kbinfo KB329067
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