This step-by-step article explains how to turn on or turn off the circular logging feature. You can control circular logging at the storage group level, which allows each storage group to have a different policy for logging.
Circular logging allows Exchange Server to overwrite transaction log files after the data that the log files contain has been committed to the database. However, if circular logging is enabled, you can recover Exchange Server data only up until the last full backup.
Microsoft Exchange 2000 Server Standard Edition, Microsoft Exchange Server 2003 Enterprise Edition, Microsoft Exchange Server 2003 Standard Edition, Microsoft Windows Small Business Server 2003 Premium Edition, Microsoft Windows Small Business Server 2003 Standard Edition