Trouble in Opening MDF File because it Says SQL Error 5171? - A guest Post by Andre Williams

MS SQL Server is the most widely used and deployed database server in organizations. But, there are times when the SQL Server database gets corrupted due to various reasons. Error messages like SQL Error 1571 are also frequent with SQL Server. Let’s learn more about the SQL error 1571, its reasons and solutions.

Symptoms of SQL Error 5171:
With SQL Error 5171, you may face failures while logging in to SQL Server, restoring SQL database files, creating a tempdb database, and attaching MDF files successfully to the SQL Server database. Instead you will receive an error saying – “.mdf is not a primary database file. (Microsoft SQL server 5171)”

Possible Reasons for SQL Error 5171:
MDF file saves data in the form of pages, and each page occupies space of 8KB. The initial first page is the header page containing important database details such as signature, file size, compatibility, and much more. Rest all the other pages stores the actual data.
When the header page or related page of the file does not get recognized by the SQL Server database, it results in the SQL Error 1571 as the entire MDF is not considered to be a valid file.

Solution to Fix SQL Error 5171:
There are multiple reasons due to which SQL Error 5171 occurs. Some scenarios are mentioned below with their possible fix solution.

Scenario 1:
Usage of a mirror database in MS SQL Server by a user encounters the Error 5171, when database is set online by executing ALTER DATABASE command

Scenario 2:
When the SQL Server is upgraded to a latest or newer version, there are possible chances of Error 5171. As, you will have to first detach the database and then upgrade it to the new version. Hence, when you will try to attach it back to the MS SQL Server, it will fail to do so and error 5171 might encounter.

Below mentioned are the possible solutions for this error:

Method 1: For database mirroring
Step 1: First set, the principal database
Step 2: Use ALTER DATABASE MODIFY FILE command to modify the information.
Step 3: Now, stop the SQL server instance.
Step 4: Copy MDF and LDF files in a separate directory
Step 5: Now, restart SQL Server and attach the database files

Method 2: For attaching the database
Step 1: To troubleshoot the error, use the sp_attach_db command
Step 2: The command will attach the detached database files after upgrading is completed.
Please note: This method will work only in the case where you have used the sp_detach_db command to detach the database

Method 3: Automated Method to FIX SQL Server Error 5171
The above methods can easily remove the SQL Error 5171. However, if you still face the error after trying the above workaround methods, then you can opt for the automated solution. You can use Kernel for SQL Database Recovery tool, one of the most recommended methods by the database experts. The tool smoothly repairs and recovers all the database objects of corrupt or inaccessible MDF and NDF files. It flawlessly recovers large-sized MDF and NDF files.

Final Words:

You can always opt to use the manual methods for SQL recovery if you are an experienced database professional. But if you’re a naïve user of SQL database and you are not skilled enough to understand the errors of the database, then we suggest you restore your database files with the help of the automated solution.  

Hope the solutions help you to resolve the issues related to MS SQL Server. If you have any queries, please mention in the comments. We will get back to you with a possible resolution.

About Andre Williams

Andre Williams, with more than three year's experience in SQL related technologies, contributes articles, blogs, and how-to tips regularly.

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