A Quick Overview of Differential Backups in SQL Server

Learn all about differential backups; their working, and when to put them to use.

Differential Backups In SQL ServerSQL Server databases are the ones which are not used for storing any ordinary data. All the medium, small, as well as the enterprise level organizations that make use of this software, also give equal importance and emphasis to the backups of these databases. Backing up SQL Server databases is one of the most important things you need to do when using them. And when it comes to backing up SQL Server data, there are three broad types of database backups: Full backups, Differential Backups, and Log Backups. In this article we will limit our focus to just Differential Backups.

What are Differential Backups how do they work?

Differential BackupsDifferential backups, as the name suggests are the kind of backup option to take care of the differences between a full backup to another backup. A differential backup is the one that takes into account all the changes that have been made to the database after the full backup. So from the time of the last full backup, to the time of the differential backup, all the changes that have been made will be backed up. And after you have made a differential backup, and plan to take another differential backup, then it will incorporate all the changes from the first differential backup, and the ones done after it. It thus renders the first differential backup as useless.

To understand the working of these backups, you first need to understand the concept of extents. One single extent consists of eight, 8KB pages, thus equalling to 64KB. Everytime some changes have been made, a flag is activated that informs SQL Server about the changes that were made after the full backup, and need to be incorporated. Incase of full backups, these flags are deactivated. Everytime you make a differential backup, it will include all extents to which changes have been made. When restoring backups, you should restore just the full backup and the latest differential backup.

Why is it Important to use Differential Backup, and when should you use them?

Differential backups can be taken more regularly than full backups, they are important because they do not take up great amount of space and successfully store all the recent changes that have been made to the database. Differential backups, along with consuming less space also take up less amount of time, this is one of the reason why they are, and should be frequently used.

If you are running the database in Simple recovery model, you can opt for running differential backup, as well as full backup. Although this will not allow point in time recovery, but you will still be able to restore recent data. For complete data safety, invest in a tool to fix corrupt sql.

If you are running the database in Bulk-logged or full recovery model, you can still make use of differential backups, for the purpose of limiting the transaction logs that will require storage. When you are restoring backup, you will have to restore only that transaction log that was created after the last differential backup.

Author Introduction:

Victor Simon is a data recovery expert in DataNumen, Inc., which is the world leader in data recovery technologies, including repair accdb and sql recovery software products. For more information visit https://www.datanumen.com/

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