The log files are critical to Exchange's recoverability. But that is exactly the wrong thing to do when it comes to Exchange transaction logs.

The intuitive thing to do if a drive is full is to delete files to free up space. In looking over cases opened with Microsoft Product Support Services (PSS), we discovered that a surprising percentage of Exchange disaster recovery cases are triggered by an Exchange log drive filling up. This post will explain best practices for managing log drive disk space and tell you how to determine which log files you can safely move if your log drive does fill up. Remove only log files that are older than the current checkpoint.

Do not remove all the log files, even if the databases have been shut down cleanly.

Move them to a different drive so that you can get them back if they are needed. There are two basic rules to follow when freeing up space on a log drive: Before you can re-mount any of the databases, you must free up some space on the transaction log drive.

If the drive fills up, all Exchange databases in an affected storage group will dismount.

Most Exchange administrators keep Exchange transaction log files on a dedicated drive. Every change made to an Exchange database must first be written in a transaction log file.

Disk drive full but no files