About backing up all or only uncommitted Exchange transaction log files with snapshot backups

Article:HOWTO71969  |  Created: 2012-02-09  |  Updated: 2012-02-14  |  Article URL http://www.symantec.com/docs/HOWTO71969
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About backing up all or only uncommitted Exchange transaction log files with snapshot backups

The Back up option for log files during full backups determines how many log files are backed up during a full or user-directed snapshot backup. You can adjust this setting in the host properties for the Exchange client.

Note:

In NetBackup 7.0, the default option is now Back up all log files (including committed log files). If you previously changed this setting for a client, your selection remains the same. For new installations of NetBackup, the default is changed to Back up all log files (including committed log files). For upgrade installations where you did not change this setting for a client, the default is changed to Back up all log files (including committed log files)

If you select Back up only uncommitted log files NetBackup only backs up and catalogs the transaction log files that were not committed to the Exchange database at the time that the snapshot was taken. Exchange requires these uncommitted log files during the recovery of the Exchange database to make the database consistent. If Back up all log files (including committed log files) is selected, all of the log files that exist on the snapshot volume are backed up and cataloged.

Back up only uncommitted log files is not recommended for replicated environments. See the following TechNote:

http://www.symantec.com/docs/TECH88101

When you back up only the uncommitted log files, the advantage is that less space is needed on the storage unit for the transaction logs. When you back up all of the log files, the advantage is that a consecutive set of log files is maintained. A previous full backup can use these log files for rolling forward. These options do not affect the ability to recover the current full or user-directed type backup. These options do affect the ability to roll forward from a previous full or user-directed type backup.

For example, consider if a full backup is performed, followed by two differential backups, followed by another full backup. If Back up all log files is specified, all of the log files exist in backup images. The first full backup, the log files from the two differential backups, and the log files from the second full backup can be restored. The existence of all the log files allows for a roll-forward recovery. If you select Back up only uncommitted log files, a gap exists in the sequence of transaction logs that are in the backup images. From the full backup, you can restore only as far as the time that is covered in the two differential backups.

For more information on how to configure the client host properties, see the following topic:

See Configuring host properties for Exchange clients.


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