Log Backup In Sql Server

Log Backup In Sql Server – In the previous articles in this series (see TOC below), we discussed the basic concept of SQL Server transaction, the internal structure of the SQL Server transaction log, and finally the best practices for managing the virtual log file and VLFs. In this article, we will examine the relationship between the SQL Server transaction log and three database recovery models.

A recovery model is a database property that defines how the SQL Server engine treats database transaction logs.

Log Backup In Sql Server

Log Backup In Sql Server

SQL Server has three recovery models: full, bulk-logged, and simple recovery models. To gain a deeper understanding of these recovery models, we discuss each recovery model separately as it relates to the SQL Server transaction log.

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The recovery model of the newly created database is the same as the recovery model of the system database. You can change the recovery model of an existing database using SQL Server Management Studio from the Options page of the Database Properties window.

Log Backup In Sql Server

To do this, right-click on the database and select “Properties”. From the Database Properties window, go to the Options page and select a new database recovery model from the Recovery Model drop-down list as shown below:

When a database is configured with a simple recovery model, the SQL Server engine stores SQL transaction logs in a transaction log file for a short period of time while a transaction is active. After SQL Server writes transaction log entries from the buffer cache to the SQL transaction log file on disk, the log is truncated when a checkpoint operation is performed to commit transactions. For more information about checkpoints, check Database checkpoints.

Log Backup In Sql Server

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A database with a simple recovery model supports only two types of backups, full backups and differential backups, excluding SQL Server transaction log backups. Administering and managing databases with the simple recovery model You can consider the advantages of the simple recovery model, which deals with trunking and automatic reuse of SQL transaction log files.

This scenario is not always true, as the inability to back up the SQL Server transaction log for a database means that a database with a simple recovery model is more likely to experience data loss because corrupted data the database cannot be restored with normal. Recovery model for a specific time. Instead, you can only restore a full backup or a time-lapse differential backup.

Log Backup In Sql Server

For example, the last full backup was taken today at 12:00 PM, the last differential backup was taken at 12:00 PM, and the database crash occurred at 6:00 PM. All database changes made in the last 6 hours will be lost. This large amount of data loss is unacceptable for mass transaction production systems. In some cases, this is acceptable for databases designed for read-only or with minimal changes to data, unless you increase the frequency of full or differential backup operations, which in most cases is possible due to backup performance it’s not. Additional benefits.

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On the other hand, because SQL transaction logs are not stored in a SQL Server transaction, a database with a simple recovery model does not participate in high availability and disaster recovery solutions such as log shipping, database mirroring, and Always-Available Groups. A log file after a transaction.

Log Backup In Sql Server

If the database is configured with a full recovery model, the SQL Server engine keeps the transaction logs in the SQL transaction log file inactive until the transaction is committed and the checkpoint operation is performed and the SQL transaction log is backed up. .

On the administrative side, additional effort is required to monitor and manage the size of the SQL transaction log file and prevent it from running out of space or filling up disk. This can be done by automating the SQL transaction log backup management plan to prune the inactive portion of the SQL transaction log and include it in a full backup strategy with full and differential backup jobs. For more information about managing the SQL transaction log, check Managing SQL Server transaction logs.

Log Backup In Sql Server

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If you keep an open mind, you will see that there is a great benefit behind this extra effort. Placing transaction log entries into a SQL transaction log file allows us to create high availability and disaster recovery solutions through database mirroring, log shipping, or always-on availability groups.

In addition, backup files created from a complete backup strategy plan, including full, differential, and SQL transaction log backups, and scheduled based on the company’s disaster recovery plan, can be easily used for point-in-time database recovery. In time, in case of database failure or corruption. With proper planning of the combination of the three backup types, any chance of data loss can be minimized or completely avoided, making it the best choice for production environments.

Log Backup In Sql Server

In the example discussed earlier, the last full backup was taken at 12:00 PM, the last differential backup was taken at 12:00 PM, and the last hourly SQL transaction log backup was taken at 6:00 PM. If a database crash occurs at 6:05 p.m., by restoring the last full backup, the last differential backup, and the SQL transaction log backup between 12:00 and 6:00 p.m., the data loss is only there will be changes made in the last 5 years. 6 hours of non-data loss minutes are accepted as follows in a production environment:

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The third recovery model in SQL Server is the least commonly used, publicly documented recovery model. This is a special-purpose recovery model in which SQL Server Engine treats transaction logs exactly as described in the full recovery model, except for the procedure followed to log bulk insert and edit operations.

Log Backup In Sql Server

When configuring a database with a bulk-logged recovery model, the SQL Server engine uses minimal logging methods to log bulk data change and insert operations. Minimal logging means logging only the data necessary for transaction recovery, without support for rollback time, which provides the best performance and consumes the least amount of space during large-scale batch operations. These bulk operations include bulk insert, select, and index rebuild operations.

It is not recommended to store the database in the mass-recorded recovery model for long periods of time. There can be a very short transition period from the full recovery model to the mass delayed recovery model when you plan to perform bulk operations, and then switch to the full recovery model when the bulk operation is complete. To avoid data loss, backup the SQL transaction log directly before switching from a full recovery model to a bulk log and another after switching from a bulk log to a full recovery model It is recommended to take a backup of the SQL transaction log. This way, you can minimize data loss by ensuring that the least number of transaction logs are logged, including bulk transactions that are logged.

Log Backup In Sql Server

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The figure below shows the steps that should be followed to achieve the best performance during batch operations and to minimize the possibility of data loss in case of any database corruption issue:

Once you understand the relationship between the SQL Server transaction log and recovery models, you’re ready to move on to the next article, where we explain the relationship between the SQL Server transaction log and different types of high availability and disaster recovery solutions. Follow the news, stay informed; Stay with us!

Log Backup In Sql Server

Ahmed Yaseen is a Microsoft Big Data Engineer with deep knowledge and experience in SQL BI, SQL Server Database Administration and Development.

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He is a Microsoft Certified Solution Expert in Data Management and Analytics, a Microsoft Certified Solution Expert in SQL Database Management and Development, an Azure Developer Associate, and a Microsoft Certified Trainer.

Log Backup In Sql Server

© 2023 Quest Software Inc. All rights reserved. | GDPR | Terms of Use | Confidentiality To understand the importance of backing up and restoring SQL Server, imagine a situation where one of your colleagues creates an SQL statement without a clause and executes it. This will erase all data.

If such a query is executed in a test environment, any luck if it is run in a production environment? A disaster has struck your organization, and all management and customers rush to the IT staff to solve the problem.

Log Backup In Sql Server

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In this situation, SQL Server backup and recovery is a crucial aspect of any DBA’s career. It could be the difference between winning and losing your job. For a DBA, when the database is corrupted and the data is deleted, deleted or the database is offline, it is very important to restore the database to a normal state without any errors or corruptions.

It is not

Log Backup In Sql Server

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