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On a Microsoft Exchange Server 2007 server, you create many Offline Address Books (OABs). After that, you may notice that the Microsoft Exchange File Distribution service uses lots of memory and processor time on a computer that has Microsoft Exchange Server 2007 Client Access Server (CAS) role installed. When this occurs, the Exchange 2007 CAS computer responds slowly and does not perform as expected.
Note The exact number of OABs that causes the problem depends on the server resources. For example, this problem may occur if there are more than 12,000 OABs. Typically, this problem occurs in a hosting environment.
When Exchange Server 2007 processes OABs, the Exchange 2007 server uses temporary objects. However, those temporary objects are not controlled well. This may cause the size of the temporary objects to grow larger than expected on the computer.
To resolve this problem, install Update Rollup 6 for Exchange 2007 Service Pack 1. For more information about Update Rollup 6 for Exchange Server 2007 Service Pack 1, see the following Exchange Help topic: