The MAPI Restrict operation is used to select items that match particular criteria. The server creates a view that is, effectively, a table with associated criteria called a restriction. If the view that has a matching restriction already exists, the server uses the existing view to satisfy the user request. Using this view is relatively inexpensive; however, creating a new view is relatively expensive. By default, the store caches only 11 views for each folder. If the server is asked to create a twelfth view, it deletes the oldest cached view and create a new view. Views add overhead to all actions on items that match the views restriction.

Client applications use the MAPI operations SeekRow or FindRow to move the cursor between rows in a view. SeekRow specifies how many rows to move the cursor, and is very low-cost in terms of CPU time. FindRow is quite expensive because it moves the cursor to the first item in a non-materialized (won't be cached) view that matches the restriction criteria, and then discards the view after the client application is finished with the action. The ultimate CPU cost of FindRow depends on the complexity of the restriction, and how many rows the store has to review before finding the first item that matches the criteria and so is loosely correlated with the number of items in the folder.

The high cost that can occur with Restrict and FindRow makes these good candidates for running cached mode which would get the cost off the server. Be aware that, sometimes, the high CPU percentage consumed by these may just be caused by shared calendars, in which case cached mode won’t help. High consumption of percentage of CPU time by these operations could indicate a lot of view creation, expensive views, or large folder item counts.