Within Full Recovery, it is only the data in the system since the last Log backup that is lost. This is because the log is truncated after each checkpoint (an automated process that cleans up memory and transactions within SQL Server). Within Simple Recovery, all the data since the last Full or Differential backup will be lost. The RPO more or less defines the amount of information that the business could tolerate losing. You may need to work with the business to define the Recovery Point Objective (RPO). It is the requirements of the business that determine whether you need the Full or Simple Recovery model. I’m going to focus on the two primary models within this article. The overriding majority of people use either the Simple or Full-Recovery Model. While the Bulk-logged Recovery Model can somewhat reduce the size of logs, the limitations it places on point-in-time recovery make it less viable for most databases on most systems. The log can only be truncated with a log backup operation. Point-in-time recovery is possible as long as no minimally logged operations are in any of the required log backups.įull: All transactions are written to the log. No point-in-time recovery is possible.īulk-logged: All transactions are written to the log except certain types of minimally logged operations such as BULK INSERT and INSERT INTO. After a checkpoint, all committed transactions are automatically removed from the log, also known as truncating the log. Simple: All transactions are written to the log. The methods of transaction log management are controlled by the database Recovery Models. Recovery ModelsĪll backups within SQL Server are affected by transactions and transaction log management. In order to get started with SQL Server backups, you first need to first understand the recovery models offered by SQL Server. This article will ensure that you have the information you need to get backups in place on your systems but there’s even more to learn about the processes within SQL Server that underlie the backup. However, database backups present a very complex topic. Most of the fundamental backup mechanisms and some of the more advanced ones are covered in this article. These are far outside the scope of this article. There are some large scale systems that will need to work with non-standard backup mechanisms such as SAN snapshots. For this reason, you should, in most circumstances, use the native backup processes or, third party tools that work directly with the native processes such as Red Gate SQL Backup. Simply copying the files that define a database will not deal with transactions and can lead to serious data corruption. This copy will be created in such a way as to deal with transactions that are ‘in flight,’ that have not yet been completed.
They are a very specific type of copy that is aware of the transactional nature of SQL Server. The same applies to SQL Server database backups to an extent, but database backups are not simply a file copy. BackupsĪ backup is nothing more than a copy that is created as a type of insurance policy in the event that the original goes away. However, the solution to the business problem is through technical means, the various backup processes offered by SQL Server 2014. That issue makes backups a fundamental business problem, not a technical one. Inappropriate, missing, or untested backups can actually cause the entire business to fail.
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Getting SQL Server backups right is the single most important thing that a data professional can do for the business they work for. SQL Server 2014 Backup Basics - Simple Talk
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