How to Restore SQL Server Database from bak File

This article provides a comprehensive guide on restoring a SQL Server database from a bak file. It covers the common problems faced during restoration, their causes, and various solutions. Additionally, it recommends software tools and answers frequently asked questions.

Nene Aly

By Nene Aly / Updated on March 5, 2024

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Restoring a SQL Server database from a bak file is a critical process for database administrators. This article aims to guide you through the step-by-step process of restoring a database and provide solutions to common problems encountered during the restoration.

Problem: Database Restoration Failure

One of the most common problems faced during the restoration of a SQL Server database from a bak file is the failure of restoration. This can occur due to several reasons:

Cause 1: Incorrect Backup File

One possible cause of restoration failure is using an incorrect or incompatible backup file format. If the backup file was created using a different SQL Server version or compression settings, it may not be compatible with the current SQL Server instance.

Cause 2: Insufficient Disk Space

If the disk space on the server is insufficient to restore the database, the restoration process may fail. This can happen if the backup file is significantly larger than the available free space.

Cause 3: Database Corruption

Database corruption can also lead to restoration failures. If the backup file itself is corrupted or contains corrupted data, the restoration process may not complete successfully. This can happen due to various reasons, such as hardware failures or software issues.

Solution 1: Verify Backup File Compatibility

To ensure successful restoration, it is essential to verify the compatibility of the backup file. Follow these steps:

  1. Check the SQL Server version of the backup file
  2. Confirm that the current SQL Server instance is of the same version or higher
  3. If the versions are different, upgrade the SQL Server instance or obtain a compatible backup file
  4. Ensure that the backup file compression settings match the restoration settings
  5. If necessary, decompress the backup file before restoration

Solution 2: Free Up Disk Space

If disk space is a concern, follow these steps to free up space:

  1. Delete unnecessary files or move them to another storage device
  2. Check for large temporary files and delete them
  3. Resize the existing database files to reclaim unused space
  4. Consider adding additional storage devices or expanding existing ones
  5. If possible, move the backup file to a different server with sufficient disk space

Solution 3: Repair Corrupted Backup File

If the backup file itself is corrupted, you can attempt to repair it using the following steps:

  1. Restore a previous known good backup file
  2. Use third-party database repair tools to fix the backup file
  3. Verify the integrity of the backup file using SQL Server tools like DBCC CHECKDB
  4. Attempt to repair the backup file using built-in SQL Server repair functions
  5. Consult with a database recovery specialist if all else fails

Recommendation: SQL Backup and Restore Software

A highly recommended software tool for SQL Server database backup and restoration is AOMEI Backupper. This software offers various features:

  • Pro: Easy to use interface with intuitive backup and restoration workflows
  • Pro: Supports multiple compression options to reduce backup file size
  • Pro: Allows scheduling of automatic backups to ensure data integrity
  • Con: Paid software with a limited free trial version

To use AOMEI Backupper:

  1. Download and install AOMEI Backupper from the official website
  2. Launch the software and connect to your SQL Server instance
  3. Select the database you want to back up
  4. Choose the backup destination and compression options
  5. Initiate the backup process and save the bak file

FAQ (Frequently Asked Questions)

Q: How long does it take to restore a SQL Server database?

A: The time required to restore a SQL Server database depends on several factors, such as the size of the database, hardware specifications, and overall server performance. Larger databases may take longer to restore.

Q: Can I restore a SQL Server database on a different server?

A: Yes, you can restore a SQL Server database on a different server as long as the target server has the necessary SQL Server version and required disk space. You may also need to adjust file paths and configurations accordingly.

Q: What is the difference between a bak file and an mdf file?

A: A bak file is a backup file created using SQL Server's native backup functionality. It contains a compressed version of the database backup, including both the schema and the data. On the other hand, an mdf file is the primary data file of a SQL Server database that stores the actual data and database schema.

Q: How can I automate the SQL Server database restoration process?

A: You can automate the SQL Server database restoration process by creating scheduled jobs or using third-party software tools like SQL Backup Master. These tools offer features to schedule regular backups and automate the restoration process.

Q: What should I do if the restoration process fails?

A: If the restoration process fails, you should assess the error message provided by SQL Server and troubleshoot accordingly. Refer to the SQL Server documentation, online forums, or seek assistance from database administrators to identify and resolve the specific issue.

Q: Can I restore a SQL Server database without a backup?

A: Unfortunately, you cannot restore a SQL Server database without a backup. Having a valid backup is essential for restoring a database in case of data loss, corruption, or other disasters.

Q: How can I check the integrity of a SQL Server backup file?

A: You can use SQL Server's built-in DBCC CHECKDB command to check the integrity of a backup file. Execute the following command: DBCC CHECKDB ('C:pathtobackup.bak'), replacing the file path with your actual backup file path.

Technical Terms

1. SQL Server: A relational database management system (RDBMS) developed by Microsoft, used to store, retrieve, and manage data in various applications.

2. Database Restoration: The process of recovering a database from a backup to its original or preferred state after a data loss or corruption event.

3. Bak File: A file extension representing a compressed backup file in SQL Server, containing a copy of the database in a specialized format.


1. Regularly schedule database backups to prevent data loss.

2. Verify the backup file before restoration to ensure compatibility and integrity.

3. Keep sufficient free disk space available for storing the backup files and restored databases.


Restoring a SQL Server database from a bak file is a crucial task for ensuring data integrity and consistency. By following the step-by-step solutions provided in this article and using recommended software tools like AOMEI Backupper, you can overcome common restoration problems and successfully restore your databases.

Nene Aly
Nene Aly · Editor