Less Than Seven Days of Log Space Left

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2006-04-13

The Microsoft Exchange Server Analyzer Tool estimates the time that remains before the transaction log drive space on an Exchange Server storage group will be full. The Exchange Server Analyzer estimates the time for the log drive to reach capacity by checking the timestamps on transaction log files on the drive. When the Exchange Server Analyzer finds that less than seven days remain before the log drive becomes full, the Exchange Server Analyzer displays an error.

The drive housing the log files for the Exchange Server databases is running out of disk space.

When log drive runs out of drive space, the following problems can occur:

  • The database will not start or will shutdown.

  • The database will go into a dirty shutdown and become inconsistent.

  • Users will be unable to access mail and or public folders.

The log drive space may become full because circular logging is disabled. Therefore, transaction log files are left on the drive until a full or incremental online backup that uses Exchange Server-aware backup software is performed.

In versions of Exchange Server earlier than Exchange 2003, databases may not be able to reach Clean Shutdown state before they stop. Two reserve transaction log files, Res1.log and Res2.log, are converted to ordinary transaction logs in a disk space emergency.

In Exchange Server 2003, optimizations were implemented so that the databases can be shut down cleanly until the reserve log files are exhausted. When a database has not been shut down cleanly, it is very important that the last several transaction logs associated with the database not be deleted. These transaction logs still contain information that must be applied to the database to restore it to consistency. If you delete these log files, the database cannot be started again until you have repaired or restored it.

If all databases in a storage group are in a Clean Shutdown state, the removal of all transaction logs will not prevent the databases from starting. However, if you remove the transaction logs, this will invalidate previous backups. This removal does not mean that previous backups cannot be restored. It does mean that you will not be able to roll a restored database forward past the point at which the log files were deleted.

The log space wizard in the Exchange Server Analyzer will analyze the existing transaction log files and help you move the ones that are no longer needed by the database. The log space wizard will also make sure that even if all databases are in a Clean Shutdown state, the current log file is not removed. If the current log file is not removed, the previous backups will remain valid.

To regain log drive space, you should remove unnecessary log files. The following actions are recommended.

To regain log drive space when log drive space is full or nearing capacity

  • Take an Exchange-aware online streaming backup or Volume Shadow Copy Service (VSS) backup of the database. For more information about VSS backup, see "Best Practices for Using Volume Shadow Copy Service with Exchange Server 2003" (http://go.microsoft.com/fwlink/?LinkId=56571).


    The preferred method for clearing unnecessary log files is to take an online streaming backup or a VSS backup.

  • If the database shuts down because it is about to run out of log drive space, you can use the Exchange Server Analyzer log space management wizard. You can use the wizard to move excess log files. Alternatively, you can manually move excess log files before you remount the database.

    To manually remove log files, follow the procedures and recommendations in Microsoft Knowledge Base article 240145, "How to remove Exchange Server transaction log files" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=240145).