BA6992: The reverse-incremental log is corrupt and the backup chain could not be repaired¶
| Error code | Product | Applies to |
|---|---|---|
| BA6992 | BackupAssist | For BackupAssist 15.0.5 or later. |
Description¶
A System Protection backup that uses a reverse-incremental scheme keeps the newest backup as a full image and stores older backups as reverse differences from it. Each backup records the reverse-merge of the previous image in a small log file, so that if a backup is interrupted the next run can automatically resume or roll back the incomplete merge.
BA6992 is reported when that log for the previous backup is found to be corrupt or unreadable and the backup could not repair the chain by any automatic means - it could neither resume nor roll back the interrupted merge, nor rebuild the previous image from the snapshot data stored in the backup. When this happens the job cannot continue building on the existing chain.
Common causes:
- The connection to the destination was lost during the previous backup - for example a NAS or network share dropped while the backup was finishing.
- The destination ran critically low on free space during the reverse-incremental merge step.
- The source volume's shadow copy that the automatic repair needs was deleted or had expired before the next backup ran.
- An underlying storage or file-system error damaged the log or the backup files.
Resolution¶
Resolution 1 - Verify older restore points and re-seed the job (recommended)¶
- Before relying on them, verify the existing restore points for this job - restore a representative file or perform a test restore to confirm the older restore points are intact, as they may be incomplete after this failure.
- Re-seed the job by running it again so it creates a new full backup. The backup chain resumes from that new full image and subsequent backups run normally.
Resolution 2 - Address the underlying cause¶
So the condition does not recur, resolve what interrupted the previous backup: free up space on the destination, or stabilise the connection to a NAS or network destination (cabling, drivers, power management, or the device itself).
Resolution 3 - Contact technical support (advanced)¶
If the job repeatedly reports BA6992, or the older restore points do not verify, contact BackupAssist Support with the job's diagnostics before re-seeding so the cause can be confirmed.
Note on the backup report¶
This condition appears in the backup report as: The reverse-incremental log of the previous backup is corrupt and the backup chain could not be repaired. Older restore points for this job may be incomplete. Verify them before relying on them and contact support. To resume backups, the job must be re-seeded with a new full backup.
BA6992 is reported with an "Errors occurred" status. It is only raised when the log is corrupt and every automatic repair has failed - a backup that successfully resumes, rolls back, or rebuilds the previous image from its snapshot completes without this condition.
| Last updated | Created | Further assistance |
|---|---|---|
| 6th Aug 2026 | 6th Aug 2026 | BackupAssist Support page |