SQL Error 5171: MDF is not a primary database file.

Applies to: Error 5171 in MS SQL Server 2017, 2016, 2014, 2012, 2008, and others.

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SQL Server error 5171: MDF is not a primary database file.

If you receive this error message, it means that you've encountered database error 5171 on your SQL Server:

"ABC.mdf is not a primary database file. (Microsoft SQL Server, Error: 5171)"

Error 5171 is a common issue encountered by many SQL Server administrators when attempting to log in to SQL or while restoring an MS SQL database. This error can also occur when the 'TempDB' database fails to create or when an MDF file cannot be attached to a database.

To resolve this error, you should first investigate the cause to determine the appropriate solution:

• MDF file is corrupted or not recognized
• Invalid registry entries
• Virus infection
• Power failure
• Damaged drivers

If error 5171 is due to the last four reasons, it is suggested to modify registry entries, remove viruses, restart SQL, check power connections, and update drivers. If the issue lies with the MDF database file, continue reading to find two solutions to resolve this problem.

Solution 1: Repair the MDF file using a SQL Recovery Tool

This error in SQL occurs when the MDF file is corrupted or records saved in the MDF file are lost.

A quick and secure solution is to repair the MDF file using a reliable SQL Recovery tool. Make sure that when you search for such a tool online, you opt for one offered by an experienced company. Additionally, it should be risk-free, 100% clean, and backed by a strong technical support team.

Equipped with vast experience in data recovery, the company recently launched SQL Recovery software to assist SQL Server administrators.

With it, you can easily repair a damaged database, restore MDF files, and even recover deleted records in SQL. Follow the steps below to fix a corrupted MDF file:

Step 1: Stop the MS SQL Server service

Press the "Windows Key + R" and type in services.msc.

Locate and double-click on "SQL Server (Instance Name)"

In the Properties window, click Stop to stop SQL Server, and then click Apply to confirm.

Step 2: Run the SQL Repair Tool. On the main interface, click on 'Browse' (two dots) to select the corrupt MDF/NDF file. Thereafter, click on 'Repair' to start the analysis of your MDF/NDF file.

If you know where the file is located, click Browse to locate the database.

If you do not know the location, click Search to search for the .mdff or .ndf file.

Step 3: Once the scan is complete, all database objects will be displayed on the left pane. Select the database objects that you need to repair and click on 'Export'.

Select Database Objects

Step 4: Choose the method to export your database data: “Export to Database” or “Export as SQL script.” If you choose “Export to Database,” you will need to provide server information, log in to your account, and select the target database, which can be either new or existing.

Step 5: Before you click OK, you need to restart SQL Server now.

Press the "Windows + R" keys and type services.msc.

Locate and double-click "SQL Server (Instance Name)"

In the Properties window, click Start to restart the SQL Server service, and then click OK to confirm.

Step 6: Click on 'OK' to save the repaired file to the SQL database of your choice.

After saving the repaired MDF file, restart SQL Server and log in with your password. After this, you should be able to access your MDF data and run SQL Server normally.

Solution 2: Manually Resolve SQL Server Error 5171

Alternatively, you can manually resolve this error using Microsoft SQL Server Management Studio:

Step 1: Run Microsoft SQL Server Management Studio and verify that the database is online.

If the database is offline, run the following command: ALTER DATABASE mydb SET ONLINE.

Step 2: Modify the information for the MDF file by using the ALTER DATABASE MODIFY FILE statement.

Before you continue, back up the SQL Server database.

Step 3: Right-click the running instance of SQL Server, and then choose Stop.

Step 4: Copy the MDF and LDF files to another directory.

Step 5: Then, restart the SQL Server and attach the MDF and LDF files.

Tips for Securing Your SQL Database

After resolving the SQL database error 5171, it's also crucial to know practical tips on how to protect your SQL Server databases. You may find these suggestions helpful:

1. Avoid Inappropriate SQL Server Upgrades

Avoid frequent upgrades of SQL Server. If a version is running fine on your server machine, leave it be. If you have upgraded and are running into an error such as 5171, you can run the sp_attch_db command to resolve the issue.

Scheduling Backups of SQL Server Databases

Automated SQL Server backup software - Todo Backup Advanced Server tool helps you create full backups for large SQL Server databases with ease.

3. Repair Corrupted SQL Server Database Instantly

In case of corruption in SQL Server database, apply SQL recovery tool to repair the database file and instantly retrieve all valuable data.

Conclusions

Though Error 5171 in SQL Server can be a frustrating and intricate issue, there are several steps you can take to resolve it. Some common solutions involve using SQL recovery software, such as the MS SQL Recovery tool, or manually fixing SQL errors. You may also need to consult with a database expert for additional guidance and support. Above all, remain calm, do your research, and act promptly to recover your data efficiently. With the right tools and strategies, the SQL Server Database Error 5171 should not hinder your access to crucial data again.

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