Troubleshoot Azure backup conflict with SQL database backup chain | Cannot perform a differential backup because current backup does

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This Article guide to resolve,

SQL Database backup failure due to AZURE VM Backup or Cannot perform a differential backup because current backup does not exist

This article has step by step process of

Troubleshoot Azure backup conflict with SQL database backup chain

What is AZURE VM Backup?

Azure Backup provides independent and isolated backups to guard against unintended destruction of the data on your VMs. Backups are stored in a Recovery Services vault with built-in management of recovery points. Configuration and scaling are simple, backups are optimized, and you can easily restore as needed.

As part of the backup process, a snapshot is taken, and the data is transferred to the Recovery Services vault with no impact on production workloads.

How Azure Snapshot Backup work?

  1. Azure VMs that are selected for backup, Azure Backup starts a backup job according to the backup schedule you specify.
  2. During the first backup, a backup extension is installed on the VM if the VM is running.
    1. For Windows VMs, the VMSnapshot extension is installed.
    1. For Linux VMs, the VMSnapshotLinux extension is installed.
  3. For Windows VMs that are running, Backup coordinates with Windows Volume Shadow Copy Service (VSS) to take an app-consistent snapshot of the VM.
    1. By default, Backup takes full VSS backups.

Troubleshoot SQL Server database backup – Azure Backup or Cannot perform a differential backup because current backup does

If you are taking AZURE VM Backup for your Azure VM for SQL Server using VSS Services. It will impact your SQL Server differential backup and you will receive below error in your SQL job.

Cannot perform a differential backup for database “database name”, because a current database backup does not exist.

Perform a full database backup by reissuing BACKUP DATABASE, omitting the WITH DIFFERENTIAL option

This job fails because, AZURE VM Backup takes FULL VM snapshot.

SQL Server consider this as FULL Back up and start new backup chain which cause differential backups to fail. We will receive error like

Cannot perform a differential backup because current backup does not exist.

when Azure VM backup (Recovery Vault) Azure VM backup break the backup chain generated in our weekly full back up, because of that differential backup doesn’t work.

Troubleshoot Azure backup conflict with SQL database backup chain or cannot perform a differential backup because current backup does not exist

To resolve this issue, you need to add ITEM in your server registry to take AZUMRE VM Copy only backup.

Post adding this SQL server consider AZURE VM backup as copy only and does not break SQL full backup chain generate by our backup policy.

#Run this in PowerShell window.
New-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\BcdrAgent" -Name "USEVSSCOPYBACKUP" -Value "True" -PropertyType "String"

Post adding this value in registry it will look like. If you want to do this on multiple servers’ best way to push this registry change through Group Policy(GPO).

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