How to configure quota settings for named properties and for replica identifiers in Exchange Server 2003 and in Exchange Server 2007

This article links to information about how to configure quota limits for the number of named properties (also named named props) and replica identifiers (also named replids) that can be created for a Messaging Database (MDB) in Microsoft Exchange Server 2003 and in Microsoft Exchange Server 2007.

You can configure a quota on the named properties and the replica identifiers resources to help minimize the damage from an attack on the Exchange Server 2003 computer. Without a limit on the number of named properties and of replica identifiers that can be created, an attack that is directed at an Exchange Server 2003 computer and that is meant to fill up the named properties and the replica identifiers tables to their maximum of 32,000 entries could make the computer unresponsive to client requests. These quotas minimize the effect of this kind of attack.

By default, Exchange Server 2003 has a hard quota of 16,000 named properties or replica identifiers for each MDB. You can override this setting by adding the following registry values to the registry key for each MDB (private or public) where you want to configure these settings. After you change these registry settings, you must unmount, and then remount the database before these changes become effective:

• Value name: Named Props Quota
  Value type: REG_DWORD
  Value data: positive integer between 1 and 0x7FFF
• Value name: Replids Quota
  Value type: REG_DWORD
  Value data: positive integer between 1 and 0x7FFF

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. To add the registry keys for each MDB, follow these steps:

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate the following registry subkey, where <servername> is the name of the Exchange Server 2003 computer, and where <Private-GUID> is the name of the private or public MDB where you want to configure one or more of the quotas:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<servername>\<Private-GUID>
3. In the navigation pane, right-click Private-GUID, point to New, and then click DWORD Value.
   • To configure the Named Props Quota setting:
     1. In the New Value #1 box, type Named Props Quota, and then press ENTER.
     2. Right-click Named Props Quota, and then click Modify.
     3. In the Value data box, type a positive integer between 1 and 0x7FFF, and then click OK.
   • To configure the Replids Quota setting:
     1. In the New Value #1 box, type Replids Quota, and then press ENTER.
     2. Right-click Replids Quota, and then click Modify.
     3. In the Value data box, type a positive integer between 1 and 0x7FFF, and then click OK.
4. Exit Registry Editor.
5. Start Exchange System Manager, unmount the database where you configured one or more quotas, and then remount the database.

After you configure one or more quotas, the following symptoms occur:

• A Warning event is logged when a named property or a replica identifier is created and the quota threshold is reached. This warning threshold is 20 entries less than the quota (quota minus 20). The named property or the replica identifier is successfully created, and one or both of the following event ID messages are logged in Windows Event Viewer:

  Event ID: 9666
  Type: Warning
  Category: General
  Source: msgidNamedPropsQuotaWarning
  Description: The number of named properties created for database "%1" is close to quota limit.%nCurrent number of named properties: %2%nQuota limit for named properties: %3%nUser attempting to create the named property: %4%nNamed property GUID: %5%nNamed property name/id: %6%n%n%n
  
  For more information, click http://www.microsoft.com/contentredirect.asp.

  Event ID: 9668
  Type: Warning
  Category: General
  Source:msgidReplidsQuotaWarning
  Description:The number of replica identifiers created for database "%1" is close to quota limit.%nCurrent number of replica identifiers: %2%nQuota limit for replica identifiers: %3%nUser attempting to create the replica identifier: %4%n%n%n
  
  For more information, click http://www.microsoft.com/contentredirect.asp.

• An Error event is logged when you try to create a named property or a replica identifier if the quota limit is met. In this case, the call to create the named property or the replica identifier is unsuccessful, and one or both of the following event ID messages are logged in Windows Event Viewer:

  Event ID: 9667
  Type: Error
  Category: General
  Source: msgidNamedPropsQuotaError
  Description: Failed to create a new named property for database "%1" because the number of named properties reached the quota limit (%2).%nUser attempting to create the named property: %3%nNamed property GUID: %4%nNamed property name/id: %5%n%n%n
  
  For more information, click http://www.microsoft.com/contentredirect.asp.

  Event ID: 9669
  Type: Error
  Category: General
  Source: msgidReplidsQuotaError
  Description: Failed to create a new replica identifier for database "%1" because the number of replica identifiers reached the quota limit (%2).%nUser attempting to create the replica identifier: %3%n%n%n
  
  For more information, click http://www.microsoft.com/contentredirect.asp.

Note For named properties, Messaging Database external interface (MDBEIF) clients are permitted to create new property identifiers (also named prop IDs) at startup without being subject to quota limitations. This occurs during the call to the EcAcceptClientsExternalInterface function.

Upgrade Scenario

An issue may occur when you upgrade a Microsoft Exchange 2000 Server that has a MDB with more than 16,000 named properties to Exchange Server 2003. In this case, a client may experience the following symptoms:

1. The client logs on to the newly upgraded Exchange Server 2003 computer by using Microsoft Office Outlook Web Access.
2. The client (whose mailbox is located on a store with more than 16,000 named properties) opens Calendar and creates a new calendar appointment.
3. The client tries to save the appointment.

In this case, the client receives a message that states that the action cannot be performed. An event is logged on the Exchange Server 2003 computer that indicates the specific user who tried to create the named property and the property name.

Recovery Scenario

If all replica identifiers are exhausted in a public folder store because of an attack by a user or because an Exchange Server 2003 client is malfunctioning, there is no typical method that is available to recover the replica identifiers or to increase the size of the replica identifiers table. To resolve this issue, replicate all content that is specific to the problem server to another server (replicate off). Remove the public MDB, and then enable the content to be replicated back from another server.

To resolve an issue in which all replica identifiers are exhausted in a private store because of an attack by a user or because an Exchange Server 2003 client is malfunctioning, move all mailboxes on this store to a different server, remove the private store on the source (problem) server, and then move all the users back to the original server.

For more information, visit the following Microsoft Web sites: