When was the last time you backed up Exchanage? Also, are the log files on the same volume that the database files are?
Basically what happens is that once a backup is complete typically the what ever program performed the backup will send a request to remove the database's transaction logs.
It's expected behavior with transaction logs to get truncated after certain type of Exchange backups...
Backup type |
Description |
---|---|
Backs up the databases (*.edb), transaction logs (*.log), checkpoint files (*.chk), and then truncates the transaction logs for a specific database. |
|
Backs up the database, transaction logs, and checkpoint files. Copy backups do not truncate the transaction logs for the database. |
|
Backs up the transaction logs to record changes since the last full or incremental backup, and then truncates the transaction logs. |
|
Backs up the transaction logs to record changes since the last full or incremental backup, and does not truncate the transaction logs. |
Reference: Types of backup operations for Exchange 2013 - https://msdn.microsoft.com/en-us/library/office/aa579157(v=exchg.150).aspx