This article was previously published under Q178021
This article has been archived. It is offered "as is" and will no longer be updated.
When you look in the Microsoft Exchange Server Mtadata directory, you mayfind a large number of .dat files, for example, DB000123.DAT. Many of thesefiles are only 1 byte in size. This is also true, even if the ExchangeServer message transfer agent (MTA) does not have any messages in thequeues held for delivery.
This is by product design. In Microsoft Exchange Server 5.5, the MTAcreates DAT files for all messages. After the messages have been delivered,instead of deleting the DAT files themselves, the data is deleted from theDAT files and the files are reset to 1 byte. The DAT files can be reusedfor future messages. This is done to enhance the performance of the MTAbecause creating and deleting files is a time consuming process. The numberof .dat files will reflect the maximum number of messages in the queue atany one time.