Problem: You experience performance problems when you are working with items in a large .ost (Offline Folder File) or in a large .pst (Personal Folder File) in Outlook 2007. When you perform the same operations on the large .pst or .ost file in earlier versions of Outlook, the same performance problems do not occur. You may see this behavior in the following ways:
- Outlook 2007 responds slowly when you are composing or replying to an email message.
- When you select a new folder, Outlook 2007 is slow to display the contents of the folder.
- The All Mail Items search method returns search results slowly.
These problems may occur if the .pst or .ost file is larger than 2 GB. To accommodate new features, Outlook 2007 introduced a new data structure for .pst and .ost files. In this new structure the frequency of writing data to the hard disk increases as the number of items in the .pst or .ost files increases. Additionally, the performance problems are more pronounced when the .pst or .ost file is larger than 4 GB.
Note: You cannot create a .pst or .ost file without this new Outlook 2007 data structure.
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