XFOR: Many DAT Files in the Mtadata Directory

Article translations Article translations
Article ID: 178021 - View products that this article applies to.
This article was previously published under Q178021
This article has been archived. It is offered "as is" and will no longer be updated.
Expand all | Collapse all


When you look in the Microsoft Exchange Server Mtadata directory, you may find a large number of .dat files, for example, DB000123.DAT. Many of these files are only 1 byte in size. This is also true, even if the Exchange Server message transfer agent (MTA) does not have any messages in the queues held for delivery.


This is by product design. In Microsoft Exchange Server 5.5, the MTA creates DAT files for all messages. After the messages have been delivered, instead of deleting the DAT files themselves, the data is deleted from the DAT files and the files are reset to 1 byte. The DAT files can be reused for future messages. This is done to enhance the performance of the MTA because creating and deleting files is a time consuming process. The number of .dat files will reflect the maximum number of messages in the queue at any one time.


Article ID: 178021 - Last Review: February 24, 2014 - Revision: 3.3
  • Microsoft Exchange Server 5.5 Standard Edition
kbnosurvey kbarchive kbusage KB178021

Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from smallbusiness.support.microsoft.com