The following is tip #6 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.
At the start of Exchange's backup operation several important operations occur.
Two important API calls are initiated by the backup application (this could be Windows/NT Backup or a third-party backup product such as Legato, Veritas, or CA) at this point to begin a backup operation. HrESEBackupPrepare is called to establish an RPC connection to the information store process (STORE.EXE). Also, the HrESEBackupSetup API call is made and will specify which storage groups (ESE instances) will be involved in the backup operation. ESE responds to these API calls by performing several operations. First, when a full backup operation is initialized, ESE begins by flushing all dirty pages in the ESE cache (IS buffers) to disk and halting the checkpoint. The checkpoint will not advance until the backup operation is complete. If the backup is a not a full backup (i.e., differential, incremental, or copy), the checkpoint is allowed to advance, since the backup operation will not be touching the databases.
Next, ESE will create patch files for each of the databases backed up. Patch files are used in special circumstances (transactions that require page splits and/or merges) during backup operations to ensure database integrity.
If you are running Exchange 2000 SP2, patch files are not used, since Microsoft has figured out how to avoid this requirement in the SP2 release.
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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).