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In Exchange Server, circular logging is disabled by default. In circular logging, Exchange overwrites individual transaction log files after the log files data has been committed to the database. This keeps transaction log from expanding. Thus, circular logging saves hard disk space.
By the term “circular,” we mean that the deletion of log files in rotational basis once the disk space limit is reached – in a LIFO (last-in, first-out) queue manner.
What happens when
- Circular logging is disabled: If circular logging is disabled, each log file goes into the transactional log database and so there is no limit on the maximum size of the database (no limit exists).
- Circular logging is enabled: While circular logging is enabled, the maximum size of the transactional log files is limited to 1 megabyte (MB). It is implemented by overwriting the previous log files automatically once the maximum limit is reached. Thus, transaction log database does not grow any further.
- Without a complete set of transactional log files, it is impossible to recover new data. So, circular logging is not recommended in production environments.
- While doing backups (incremental as well), enabling circular logging on Exchange database is not recommended.
- Using Exchange Management Console
- Using Exchange Management Shell
Enable circular logging in Exchange 2010 using Exchange Management Console with below few steps.
- Start Exchange Management Console
- Choose Organization Configuration, expand it and then click Mailbox
- On Database Management tab, select the database to configure
- Under database name, in action pane, click Properties
- Click Maintenance tab > select Enable circular logging check box > click OK
For Exchange 2010, you can enable circular logging by executing the following command:
Note: To make the changes to circular logging settings effective, perform any of two – Restart the Microsoft Exchange Information Storage Service, or Dismount and mount the databases.
You may encounter a condition where database storage space is filling up continuously. Once you reach a certain threshold point of storage, there could be a failure in mounting Exchange Database. Now, before going to enable circular logging to free up space in your database, you must make a copy of log and database. This must be done to have a backup of the database and to replay the logs again when required.
Can third-party tools help after Exchange data loss?
In case of a data loss, there are many alternative solutions for Exchange Server recovery. Kernel for Exchange Server is one of the best solutions to repair corrupt Exchange database files (log files not required). EDB to PST converter can also extract data from Exchange backup files.