https://ilantz.wordpress.com/2011/10/26/how-to-manually-purge-exchange-server-logs-clean-and-easy/

This example will show you how to purge the logs for a database that is located on Drive D. we will “fake backup” drive D and this will trigger the logs to be purged.

  1. Open Command prompt
  2. Launch Diskshadow
    1. Add volume d:
    2. Begin Backup
    3. Create
    4. End Backup
  3. At this step you should notice the following events in the application log indicating that the backup was indeed successful and logs will now be deleted.

Here’s some screenshots from the process:

Diskshadow commands for the example