MS Exchange Server uses a logging mechanism to record all changes to the Exchange database. These changes are stored in Exchange database transaction logs. If your database becomes corrupt, the transaction logs are used to restore the database to a consistent state. These files ensure a high level of recoverability. When some of these log files go missing or get accidentally deleted, the Exchange database may fail to mount.

For instance, you may see the following event in your Application log after your database failed to mount on the server:

Event ID: 455 Description: eseutil (4724) Error -1811 (0xfffff8ed) occurred while opening logfile drive_letter:\Program Files\Exchsrvr\MDBDATA\E00.log.

The above problem may surface if you have installed antivirus software in your system that has quarantined or deleted the current Exchange log file.

In order to work around the issue, you need to check the configuration of the antivirus software. Ensure that the software does not scan the Exchange Server directories. Also, check the log files of the software. This will help you identify if the log file was quarantined or deleted.

You can recover your log file using any of the following methods:

I. The log file was quarantined:

• You need to recover the log to the folder having production log files. • Start your Exchange Information Store service. If no other log file is missing or deleted, then the database will certainly mount. If you have other files missing, then look for them in the quarantine folder of the antivirus program. If you still can’t locate the files, then use the next method.

II. The log file was deleted:

In this case, you will require restoring the Storage Group and then playing the log files. Follow the given procedure for restoring the database:

• Transfer all the corrupt or inconsistent databases to a backup folder. • If there is a new E00.log file, then move it to the backup folder. Further, move E00.chk file to the same backup folder. • Copy the remaining log files and paste them in your backup folder. • Change the name of ‘E00*.log’ to ‘E00.log’. • Now, restore the database from this backup and then try replaying the log files to bring it back to a consistent state. The database can now be easily mounted, but does not contain the ‘E00.log’ file. • Start the Exchange Information Store service.

If your Exchange database fails to mount after using the aforementioned workarounds, take help of professional Exchange Server recovery software.

This guest post is written by Axel Culver who is working for http://www.stellarservertools.com/, a site that offers Exchange Recovery tools. These tools repair Exchange databases and restore individual user mailboxes to Outlook PST files. They support MS Exchange 2010, 2007, 2003, 2000 and 5.5.