Troubleshooting “Invalid backup chain detected” Messages
SQL Backup Master 6.3 includes a new feature called backup chain validation that is responsible for generating “invalid backup chain detected” messages. This article describes the goal and function of this feature.
Introduction
The goal of backup chain validation is to warn users when other third-party applications could potentially interfere with the SQL Server backup chain. Specifically, when a differential or transaction log backup is started, SQL Backup Master analyzes SQL Server’s backup history table and checks to see if the most recent backup was also created by SQL Backup Master.
If a possible conflict is detected, SQL Backup Master writes an “invalid backup chain detected” message to the log. Such messages can be logged as warnings (default) or errors, depending on backup job settings.
Note that copy-only database backups are ignored during backup chain validation, as they don’t interfere with the SQL Server backup chain. See below for details.
Why does it matter?
Why is it a potential problem if another software tool is also taking SQL Server backups?
In some cases, it won’t be. If a third-party software tool is taking copy-only SQL Server backups, those will not interfere with the backup chain so SQL Backup Master won’t warn about them. If you need to occasionally take a backup outside of SQL Backup Master (i.e. via SQL Server Management Studio, etc.) then creating a copy-only backup is a good option.
However, some third-party products will create snapshot backups (via Volume Shadow Copy Service) that will invalidate the backup chain. A broken backup chain can then trigger other backup errors or interfere with future restore efforts.
Troubleshooting
SQL Backup Master makes it easy to see if another software tool is taking snapshot database backups.
To start, select the Reporting tab in the main product window and select the Backup history report. Starting at around the time when SQL Backup Master logged the “invalid backup chain detected” message, look for preceding report entries with the Is Snapshot field set to True.
You can also look for report entries with a Backup set field that is not set to “SQL Backup Master backup”.
Solutions
If you’ve used the information above to determine that snapshot database backups are triggering this message, there are several possible solutions.
One option is to disable the SQL Writer system service, which VSS (Volume Shadow Copy Service) uses to create SQL Server database snapshots. To do so, Run services.msc, find the SQL Server VSS Writer service, stop it, and configure it to start up manually.
Another possible option is to determine which third-party backup solution is taking SQL Server database snapshots and configure it not to do so. For example, if you’re using Azure Backup you may wish to avoid using the SQL Server backup agent. Other Virtual Machine or cloud-based solutions may have backup features that can be similarly configured.
Finally, if you determine that the “invalid backup chain detected” messages logged by SQL Backup Master are not relevant for your environment, you can ignore them (if they’re configuring as warnings) or disable them entirely in the Database tab of the backup job settings window.
Once the problem is resolved, we recommend taking a manual full backup of any affected databases in SQL Backup Master to reset the backup chain.