Exchange Database Corruption and Torn Writes
Exchange Server maintains databases for data and log files for holding transactions. Each database contains .edb and .stm as two of its files, while the most important is .edb that contains mailboxes. If Exchange Server database gets corrupted, EDB Repair becomes need of the hour. However, if it results due to some unexpected event and database and log files are intact, through Soft Recovery user can replay the transaction logs on the database and get consistent database.
The application uses different log files like E00.log, E0000000.log, Res1.log and Res2.log. Specifically if the incomplete write operation is of E00.log, it is termed as torn write. This write is caused by operating system crash, unexpected failure, database end process or using any termination utility. If the file is healthy and issue is only torn writes, we can replay it on database and get the database repaired. But if it is damaged or issue is other than torn writes, replaying it will result as an entry in the application log like given below:
Event Type: Error
Event Source: ESE98
Event Category: Logging/Recovery
Event ID: 465
Date: 12/9/1999
Time: 2:48:48 PM
User: N/A
Computer: Computer_Name
Description: Information Store (2428) Corruption was detected during soft recovery in log file E:\exchsrvr\THIRD\E00123ab.log. The failing checksum record is located at position 8189:328. Data not matching the log-file fill pattern first appeared in sector 8195.
In such cases, database rejects the log file data and so replaying damaged log file doesn’t cause any further harm to database. To test the damage of E00.log file, eseutil /ml command can be used. However in these cases where torn writes can’t repair the damaged database (either due to factors other than torn writes or damaged E00.log), we can try any of these EDB Recovery solutions:
· In case of damaged log file, its backup copy can be restored from a recent server backup or online backup.
· We can remove all log files which are newer to the damaged log file and restore Exchange database from backup. In this case, the log file data will be lost.
· If the problem persists, a user can use /p option of Eseutil utility to perform Hard Recovery after restoring the database from online backup. The process deletes all corrupted pages from database.
· If all solutions fail, probably because of backup unavailability, we can use third party EDB Repair tools to scan and repair damaged EDB files and extract user mailboxes. The software can also be used to recover data to replace Hard Recovery process. Such recovery tools end the risk of data loss due to their read-only nature.
Stellar Phoenix Mailbox Exchange Recovery is advanced EDB Recovery software. It supports Exchange Server 2003, 2000 and 5.5. The software extracts individual mailboxes as PST files, which can be used with MS Outlook. This EDB Repair Software is compatible with Microsoft Windows XP, 2003 and 2000.
About the Author:Albert Boris, For more information, visit: http://www.edb-repair.com/
Article Source: ArticlesBase.com - Exchange Database Corruption and Torn Writes