The Symantec Backup Exec for Windows Servers Advanced Open File Option (AOFO) uses advanced open file and image technologies designed to alleviate issues that are sometimes encountered during backup operations, such as protecting open files and managing shortened backup windows.

When a job is submitted for backup with the AOFO selected, a snapshot of each volume is created, providing a point-in-time record of the data. When creating a snapshot, Backup Exec uses advanced snapshot technologies to momentarily suspend write activity to a volume so that a snapshot of the volume can be created.

If the files selected for backup reside on more than one volume, by default Backup Exec creates a snapshot for each volume that contains data to be backed up. For example, if the data to be backed up resides on a single volume, a single snapshot is created. If data resides on four volumes, four snapshots are created. After creating a snapshot, the data is backed up from the snapshots, and then the snapshots are deleted.

During the backup, files can be open and data can be changed. Depending on the snapshot provider that you are using, open files are handled using different methods.

See Best practices for using the Symantec Volume Snapshot Provider.

The following graphic shows how AOFO works.

The illustration represents the following:

1 - A backup begins for volume C on a Windows server using AOFO.

2 - A snapshot is taken of volume C, that provides a point-in-time record of the data.

3 - After the snapshot is taken, the backup job starts and the data from volume C is written to tape.

During the backup job, files can be opened, and data can change. AOFO allows data to change by making a copy of the original data, named a cache file. The snapshot tracks the data changes, as illustrated in the cache file diagram.

For example, an open file such as a Microsoft Word document contains the data A, B, and C in blocks 1, 2, and 3.

i - During the backup job, "B" changes to "D" in block 2.

ii - The original data in block 2 is copied to a cache file. In this case, "B" is the original data.

iii - The changed file is now the most current file.

When the snapshot comes to a changed block, it replaces the changed block with the original data from the cache file. The snapshot sends the point-in-time data to Backup Exec. The data is then written to tape or disk.

When the backup is complete, the snapshot is deleted.

Symantec strongly recommends that Backup Exec database agents be used to back up databases. Backup Exec database agents provide selective restores of data and more integration with the database application while preventing backups of partial transactions. Agents also enable backups on a database that is spread across multiple disk volumes.

When you select AOFO for a volume-level backup of Microsoft SQL or Exchange servers but do not use the database agents, the SQL or Exchange databases are excluded from the backup.

When you select AOFO for backup of an Oracle server, databases are backed up automatically. To avoid duplicate backups of the database files, manually exclude the database files from the backup job.

You can use AOFO on the same volume as a database to provide open file support for other applications. AOFO provides generic protection for flat files when Backup Exec agents are not used, and provides protection for Microsoft Outlook PST files.

AOFO is not available for use with Extensible Firmware Interface (EFI) system partition backups.