A synthetic backup job can cause data loss if the incremental backups within the backup definition have switched from using Windows Change Journal to the backup method for files called ‘Using catalogs’ to determine which changed files to back up.
Although a baseline full backup, an incremental backup and a synthetic full backup are completed successfully, the synthetic full backup may back up partial files only.
When this issue occurs, the bytes count of the synthetic full backup job is extremely smaller than source volume. (Figure 1)
When browsing the restore selection, some folders and files do not exist in the result of the Synthetic Full backup job. (Figure 2)
The following message is logged in the job log of the incremental backup jobs. However, the incremental backup job and the synthetic full backup job are completed successfully.
The Windows Change Journal is unavailable or incomplete. This resource will be backed up without using the Windows Change Journal.
A synthetic backup job definition is created in Backup Exec.
The full backup backs up all the files as expected.
One of the subsequent incremental backups fails to use Windows Change Journal and instead uses the backup method for files called ‘Using catalogs’ to determine which changed files to back up.
The synthetic backup that synthesizes the full backup and the subsequent incremental backups into a single set is much smaller in size than expected.
A hotfix is now available for this issue in the current version(s) of the product(s) mentioned in this article. Refer to the Hotfix link under Related Articles at the end of this article to obtain the hotfix needed to resolve the issue.
Backup Exec 2012 Rev 1798 Hotfix 213186 (TECH213186)
NOTE: After apply the hotfix the Backup Exec Remote agent must be updated on remote server where the Synthetic Backups are being performed.
New FULL Baseline Synthetic Backups must be performed.
Symantec strongly recommends the following best practices
1. Always run a backup job that includes all critical system components before you make any changes to your environment.
2. Always make sure that your environment is running the latest version and patch level.
3. Perform periodic "test" restores.
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Backup Exec 2012 with synthetic backup jobs in backup definitions