Database Fails to Start when Circular Logging is Enabled
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robertsmike
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Description
Circular logging is a Exchange Server feature that implements recycling of logs. Exchange Server writes the data to be committed to the database in transaction logs before actually writing it. If circular logging is enabled and four logs have been filled, it assumes that the first log as committed and thus, recycles the logs in order to save disk space. But it comes with a major flaw that prevents disaster recovery.
For example, you observe an unexpected shutdown with an Exchange database. After this, when you try to start it, an 'JET_errFileNotFound' error is displayed with a numerical value, such as 4294965485, -1811 or 0xfffff8ed. When you view the application event log, it shows events 1120 and 5000.
Cause
Events 1120 and 5000 generally show database inconsistency that prevent the database to start. You should see their description for the exact reason.
One probable cause could be that circular logging is enabled and error lies in checkpoint file, usually Edb.chk file. Now, if a process blocks the Edb.chk file for a considerable period of time and prevents Exchange to update it, the file may get deleted before it could be updated. Thus, the checkpoint gets lost if the database suffers an unexpected stop. When you restart the server, the Edb.chk file points to a log file that doesn't exit anymore and hence, the database doesn't start.
Solution
If the exact cause is known and the errors are occurring only because of Edb.chk file, delete it and database service. But if the cause is different, the database might get damaged.
It is suggested to use Exchange Repair products in case if no good backup is there. Exchange Repair tools are high-end and safe database repair utilities that can repair and restore a corrupted Exchange database.
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