There are three types of recovery models for SQL Server: simple recovery, complete recovery and large-capacity log recovery. 1. The simple recovery model is suitable for small changes or testing environments and does not support point-in-time recovery; 2. The complete recovery model is suitable for production environments and supports recovery to any point-in-time recovery; 3. The large-capacity log recovery model is used to reduce the log volume of large-scale operations and is an optimized version of the complete mode. The selection basis includes data change frequency, recovery requirements and business scenarios. Reasonable selection and cooperation with backup strategies can ensure data security.

The recovery model of SQL database determines the management method of transaction logs and the ability to recover data. If you are responsible for maintaining the database, or need to develop backup and recovery strategies, it is necessary to figure out the differences between different recovery models.

What is a recovery model?

SQL Server provides three recovery models: simple recovery, complete recovery, and large-capacity log recovery. The main difference between them is how the transaction log is logged and retained, which in turn affects which type of recovery operations you can perform.

• Simple recovery model : suitable for development or testing environments, does not support point-in-time recovery.
• Complete recovery model : suitable for production environments, supporting complete transaction log recovery, including to a specific point in time.
• Large-capacity log recovery model : It is an optimized version of the complete mode, mainly used to reduce the log volume of certain large-scale operations (such as batch import).

Which model to choose depends on your business needs, the frequency of data changes, and the requirements for recovery.

Scenarios and restrictions apply to simple recovery models

The biggest feature of the simple recovery model is that the transaction log will be automatically truncated after each checkpoint, and there is no need to manually manage log backups.

This sounds convenient, but it also means that you can only restore to the state of the last full or differential backup, and you cannot achieve more accurate time points.

Suitable for using simple recovery models:

• The database has little change and can accept data loss for one day or even longer.
• No frequent log backup is required.
• In a test/development environment, redoing data is more important than restoring.

But if you are dealing with systems such as bank transactions and e-commerce platforms that require high data integrity, this model is not suitable.

The complete recovery model is the first choice for production environments

The complete recovery model records all transaction operations and keeps the transaction log until you have done a log backup. This means you can restore to any point in time, even if a failure occurs after the last full backup.

To fully utilize the advantages of this model, you need to make regular full backups, differential backups and transaction log backups.

For example:

• Make a complete backup every day at 2 a.m.;
• Make a differential backup every hour;
• Make a transaction log backup every 15 minutes.

In this way, even if there is a problem, the data can be restored to a state of a few minutes before the accident occurs. Of course, this also means you have to manage more backup files and make sure the backup chain keeps cracking.

Where is the large-capacity log recovery model used?

The large-capacity log recovery model is actually designed to deal with those "one-time" large-scale operations. For example, when importing a large amount of data, rebuilding indexes, or loading a data warehouse, you do not want to make the transaction log too large, and you also want to maintain a certain recovery ability.

It does not record every row of details of these operations, but records in a minimal way, reducing log space usage. However, it should be noted that if a large batch of operations performed in this mode is not done for log backup, some operations may not be fully restored.

Therefore, it is generally recommended to switch to this mode only when performing a specific task, switch back to the complete recovery model after completion, and immediately make a log backup to re-establish the recovery chain.

Overall, choosing the right recovery model will allow you to lose a few strands of hair in the event of a failure. Simple models are easy to deal with but high risk, complete models are complex but flexible, while large-capacity models are a temporary measure in special times. Only by making reasonable choices based on your system needs and cooperating with a good backup strategy can you truly ensure data security.

Basically that's it.

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