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NetVault Plug-in for SQL Server 12.2 - User Guide

Introducing NetVault Backup Plug-in for SQL Server Planning your SQL Server deployment Installing and removing the plug-in Configuring the plug-in Backing up data
Defining a backup strategy Understanding snapshot-based backups Reviewing the compression features Performing Online VDI backups Performing VSS backups in SQL Server Example of creating a full VDI backup of an AlwaysOn Availability Group on Windows
Restoring data Using the CLI with the plug-in Troubleshooting

Incremental Transaction Log backup for Online VDI

Incremental Transaction Log backups are supported by:

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SQL Server versions: Windows - 2008 and later; Linux - 2017 and later
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Recovery Models: Full or Bulk-Logged Only

SQL Server Transaction Logs are essential to data recovery and must be backed up regularly. With Transaction Log backups, you can recover the database to a point-of-failure or specific point.

An Incremental Transaction Log backup captures all the transaction logs including those logs generated since the last Full Database/File or Filegroup, Differential Database/File or Filegroup, or Incremental Transaction Log backup. An Incremental Transaction Log backup should not be performed in the following conditions:

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Until a Full Database or Full File and Filegroup backup has been created because the transaction log contains changes made to the database after the last backup was created.
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After the transaction log has been manually truncated, until a Full Database or Differential Database backup has been performed. Microsoft strongly recommends against manually truncating transaction logs.

Tail-Log backup for Online VDI

Tail-Log backups are supported by:

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SQL Server versions: Windows - 2008 and later; Linux - 2017 and later
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Recovery models: Full Only

A Tail-Log backup captures the transaction logs that have not yet been backed up and is the last backup restored in a restore sequence. SQL Server requires you to back up the tail of the log before restoring a database that is attached to the SQL Server Instance. Therefore, a Tail-Log backup is the first step in most restore sequences.

A Tail-Log differs from an Incremental Transaction Log in the following ways:

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You can try to run a Tail-Log backup even if the database does not start, for example if the database is damaged or is offline. If the database is damaged, a Tail-Log backup succeeds only if the log files are undamaged, the database is in a state that supports Tail-Log backups, and the database does not contain any bulk-logged changes.
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A Tail-Log might contain incomplete metadata if the database is damaged because some of the metadata normally available for log backups may be unavailable in a Tail-Log backup. However, the captured log is complete and usable.

A Tail-Log's data might not be fully self-contained if the database is not online and undamaged at the time of the Tail-Log backup. Transactional data from a Tail-Log is always complete and usable, but if the Tail-Log backup is initiated while the database is damaged or offline, metadata might be only partially captured. If this issue occurs, a recovery from the Tail-Log leaves the “backupfilegroup” table missing some information about filegroups, and the “has_incomplete_metadata” column of the “backupset” table is set to 1.
 
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WARNING: Because Tail-Log backups place the databases in Offline Mode, only perform a Tail-Log backup if you are preparing to perform a restore and recovery. Tail-Log backups should not be used as a substitute for regular or unplanned Incremental Transaction Log backups.
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If you are working with an AlwaysOn Availability Group, use SQL Server Management Studio to remove the primary and secondary databases from the group before completing a Tail-Log backup. After the databases are removed from the group, their status changes to Restoring, and they are owned by the SQL Server Instance assigned the Primary Role in the group. To complete the Tail-Log backup, select the databases under the SQL Server Instance.

Full File and Filegroup backup for Online VDI

Full File and Filegroup backups are supported by:

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SQL Server versions: Windows - 2008 and later
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Recovery models: All

A Full File and Filegroup backup backs up all the data in one or more files or filegroups. A complete set of Full File and Filegroup backups is equivalent to a Full Database backup.

Full File and Filegroup backups have the following advantages over Full Database backups:

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With a Full File and Filegroup backup, you can back up and restore the files in a database individually. This process can speed up the recovery process as you can restore only damaged files without restoring the rest of the database.
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Full File and Filegroup backups increase the flexibility in dealing with large databases that contain data with varying update characteristics. For example, consider the following recommendations:
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Back up frequently modified data often.
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Back up infrequently modified data less often.
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Back up read-only data once.

The primary disadvantage of Full File and Filegroup backups is the risk that a media failure can render an entire database unrecoverable if a damaged file lacks a backup.

By default, file backups contain enough log records to roll forward the file to the end of the backup operation. Under Simple Recovery Model, the Full File and Filegroup backups are restricted to read-only secondary filegroups. You can create a file backup of a read/write filegroup, but before you can restore the read/write file backup, you must set the filegroup to read-only and take a differential read-only file backup.

Differential File and Filegroup backup for Online VDI

Differential File and Filegroup backups are supported by:

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SQL Server versions: Windows - 2008 and later
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Recovery models: All

A Differential File and Filegroup backup captures only the data changed since the last file backup. These backups are fast because the Database Engine tracks changes made since the file was last backed up, eliminating the need to scan the file.

For Simple Recovery Model databases, Differential File backups provide a faster, space-saving way to create backups of current files. Differential File backups also reduce recovery time for Full Recovery Model databases by reducing the number of transaction logs that must be restored.

Differential File and Filegroup backups should be considered when:

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You are backing up some files much less frequently than others.
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Your files are large and the data is updated infrequently, or the same data is updated repeatedly.
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