Tips to Recover Data from Exchange Database Corruption and The Role of Exchange Built-in Utilities

26 Jan

Exchange Server is designed using standard database technology. The entire system is dependent on an embedded database system for processing information. Despite being fault-tolerant and transactional-consistent, the Exchange databases may develop inconsistencies due to several unsuspected events, such as system crashes or hardware failures. As a consequence, all data stored on the Exchange Server becomes inaccessible to the users.

The problem of database corruption may surface in two ways, i.e. ‘Physical’ and ‘Logical‘. Physical corruption is a more serious concern than logical database corruption, as the latter is related to hardware failure and requires you to restore from backup. On the contrary, logical corruption is seen more often at the database level, i.e. database engine failure. It can also happen at the application level, i.e. in mailboxes, messages, attachments, and folders.

Physical corruption is easily detected by performing online backups. During the process, the database engine calculates a checksum for each 4 KB page in the database file read from the disk. If this checksum does not match with the checksum stored on the page, it throws an error indicating physical corruption. An occurrence of ‘-1018’ error indicates that you have a crappy hardware, either a bad disk or a bad disk controller. In such cases, you should perform restoration from the last good backup.

Logical corruption in Exchange databases implies an issue with the Information Store or the database engine. You should carefully examine each error, as any negligence may result in serious damage to data. The Eseutil utility and Isinteg utility can be used to repair or fix logical database corruption. You can run Eseutil against ESE database (.EDB) files, streaming (.STM) files, and log (.LOG) files in a Storage Group within the Information Store. Eseutil can be accessed from the following folder in Exchange Server 2000 and in Exchange Server 2003:

C:\Program Files\Exchsrvr\Bin

Besides repair, Eseutil can also be used for carrying out offline defragmentation and integrity checks in Exchange Server. The Repair mode of Eseutil is used to fix corruption, while the recovery and restore modes replay transaction log files into your database.

The Isinteg utility is used to rectify issues at the application level. The tool sees an Exchange database as a group of mailboxes and different items in these mailboxes. It can repair data and existing relationships between these items or entire mailboxes.

In case the above built-in Exchange tools fail to repair database corruption, you should opt for professional Exchange Server recovery software. These tools comprehensively scan the corrupt Exchange database to retrieve every piece of inaccessible information, including emails, contacts, calendars, tasks, appointments, etc.

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