XADM: Importing CAL File with Outlook Causes High Store.exe CPU Utilization

When you import a CAL file using a Microsoft Outlook client and you select either Replace Duplicates With Items Imported or Do Not Import Duplicate Items, the import process becomes progressively slower as each appointment is processed in the CAL file, and the information store CPU utilization gradually increases. After the import process is complete, the Outlook client will observe slow calendar operations (slow to create or modify appointments, and reminder notifications are slow to appear).

The Outlook client is using an inefficient process during the CAL file import to determine when duplicate items exist. This causes the information store to create structures in the database that impact the performance of operations involving the Calendar folder.

The structure created is a view (also called a filter, restricted view, or simply a restriction). A restriction can be thought of as a semi-permanent "search" query applied to a folder. The creation of a restriction is normal, but should be used sparingly because the information store caches restrictions that are created. When you create or modify a message in a folder that contains restrictions, the information store attempts to determine if any of the restrictions for that folder apply to the message. As the number of restrictions increases, the CPU overhead for processing the restrictions increases.

The creation of restrictions can be viewed by enabling maximum logging for the category of Views under MSExchangeIS - Private in Exchange Admin. With logging enabled, an Event ID 1167 will be logged with the creation of each new restriction; for example:

The following workarounds can be used to avoid or correct this condition as specified.

• If possible, select "Allow Duplicates to Be Created;" this option is selected in the Import Wizard. From the File menu, choose Import, and select the appropriate file type. After you specify the correct filename to import, you will have the option to "Allow Duplicates to Be Created;" this option is listed in a dialog box under "File to Import."
  
  -OR-
• Run ISINTEG -FIX -PRI. This causes the cached restrictions to be discarded, thereby restoring normal performance of the Calendar folders.
  
  -OR-
• Lower the value of the Aging Keep Time. The Information Store discards cached restrictions that are unused after the Aging Keep Time has been reached (default is eight days). Lowering the value causes the Information Store to discard these restrictions sooner.
  
  For additional information on the Aging Keep Time, please see the following article in the Microsoft Knowledge Base:
  
  159196  (http://support.microsoft.com/kb/159196/EN-US/ ) XADM: Tasks Controlled by the IS Maintenance Schedule
  
  -OR-
• The Information Store will discard all cached restrictions if the "Reset Views" registry value is specified with a value of 0x1 (during the next IS Maintenance process).
  
  For additional information, please see the following article in the Microsoft Knowledge Base:
  
  159196  (http://support.microsoft.com/kb/159196/EN-US/ ) XADM: Tasks Controlled by the IS Maintenance Schedule
  
  -OR-
• Move a user mailbox to another server in the Exchange Server site. Cached restrictions are not moved when the user data is moved.
  
  -OR-
• Obtain the fix mentioned below. This causes the Outlook client to use a different process to query for duplicates. This new process does not cause the creation of cached restrictions.

Microsoft has confirmed this to be a problem in Microsoft Outlook version 8.01, 8.02, and 8.03.

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.