The following is tip #2 from "20 tips on protecting and recovering Exchange data in 20 minutes," excerpted from the book, "Mission Critical Microsoft Exchange 2003" (Digital Press, a division of Elsevier, Copyright 2004). For more information about this book and other computing titles, please click here. Return to the main page for more tips on this topic.
The normal backup (also referred to as a full backup) is the fundamental unit of operation for most Exchange deployments. Regardless of the strategy you select for backup, the normal backup type will be part of your operational procedures. With a normal backup, both the database files and the log files are copied to tape. In addition, the log files are truncated or deleted once they have been copied to the backup media.
The truncation point for the transaction log files is the current database checkpoint location. The normal backup operation is also important to database integrity since only during a normal backup are the 4-KB database pages checked for corruption (they are also checked during copy backups and on-line database maintenance as well). This is accomplished by verifying each page read to make sure that the page number requested is the page the database engine received. Next, each page's CRC information (contained in the page header) is verified to ensure that the data contained in the page is valid. The normal backup is also important to the ESE Page Zeroing feature, which I will discuss later in this chapter. To restore from a normal backup, you only need to restore the complete set and allow the ESE database engine to replay any log files required for the database to be in a consistent state.
Similar to the normal backup is the copy backup. A copy backup differs in that it does not truncate or purge log files once they have been copied to tape. In addition, the copy backup does not update database backup context information contained in the database file header. Copy backups are very useful for archival purposes or other scenarios in which you want to back up your Exchange databases, but do not want to disrupt the normal backup schedule. A copy backup performs the same functions of integrity checking and page-zeroing (if enabled) as the normal backup.
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About the author: Jerry Cochran is a contributing editor for Windows IT Pro and Exchange & Outlook Administrator and a group program manager for Microsoft. He is the author of Mission-Critical Microsoft Exchange 2000 (Digital Press).