About reverting Microsoft SQL Server block-based backups

Protector can revert blocked-based backups to restore databases captured at a previous point in time. When reverting, Protector will revert all disks which are part of the block-based backup. It is not possible to revert just a single database of a block-based backup.

Tip: If you want to restore a single database from a backup, mount the database and copy the files manually.

Protector offers two revert types. The following table summarizes the benefits and disadvantages of each option:

	Pro	Contra
Offline	Supports multiple databases. Supports system databases.	Instance and all databases are temporarily offline during revert. It is not possible to apply transaction logs.
Online	Instances and other databases remain online. User has the option to apply transaction logs manually.	Online revert does not support system databases.

Offline Revert

Offline Revert can revert both user and system databases, as well as multiple databases at the same time.

During the revert, the instance and databases on the instance will be offline, making them inaccessible for users. An offline revert will detach the user database(s) which are part of the backup and revert the data on disk. For backups containing only user databases, Protector can then attach selected databases.

Note:

Reverting System databases

System databases capture the configuration of the instance. Reverting them will change the configuration of the instance to what it was at the point in time of the backup. This includes user accounts, permissions, and the list of attached databases. As a result, user databases reverted together with system databases may be attached after the revert.

The following table illustrates the status of disk, instances, and databases after a successful revert.

Table. Status after offline revert
Backup content	Disk	Instance	Reverted database(s)	Other database(s)
User database(s)	reverted	online	Depends on user selection. Options are: Detached Attached and online	Unchanged. Same as before the revert.
System database(s)	reverted	online	online	Depends on the state that is captured in the system database(s) at time of block-based backup.
Mix of system and user databases	reverted	online	System databases will be online. State of user databases depends on the state that is captured in the system databases at time of block-based backup.	Depends on the state that is captured in the system database(s) at time of block-based backup.

Online Revert

When performing an online revert, the instance as well as other databases will remain online and accessible to the user.

In addition, the user can choose if Microsoft SQL server should recover the database automatically to the point in time captured by the backup or if the user wants to apply transaction logs.

These benefits come with the additional restriction that the backup and the disks may only contain a single user database. When using online revert for multiple databases, each database must have its own set of disks. Furthermore, the databases must be backed up and reverted individually.

Reverting Clustered SQL Server instances

Protector supports reverting databases for instances using traditional clustered disks. It is not possible to revert Cluster Shared Volumes (CSV)

Prerequisites for reverting Microsoft SQL Server block-based backups

The following prerequisites must be met to revert a block-based Microsoft SQL Server database backup.

A block-based backup of a Microsoft SQL Server is available.
The backup must not be a backup from an Availability Group.
Credentials for the SQL Server instance are available. Please refer to Microsoft SQL Server User Privileges for more details.
The SQL Server node which was used to create the backup is available and online.
All nodes of the target instance are up and running.
Note: Reverting Microsoft SQL Server Availability Group backups is not supported.

Force Revert

Protector will not perform reverts in case it detects an enhanced data loss potential. If, for example, the snapshot contains multiple databases and only a single database was selected for backup, a regular revert will not be possible. Reverting the backup will revert the complete disk, which will not only affect the database selected for backup but the other databases sharing the same disks as well.

In these cases, Protector will not perform a revert unless the user specifies the force revert flag in the SQL Server Revert Wizard. Once selected Protector will ignore all safety measures and attempt the revert.

Warning: Forcing a revert is dangerous and has increased risk for data loss. Only use it when you understand why it is required and what the consequences will be. In most cases, it is a better option to mount the block-based backup and copy the data manually.