SQL Server Error: Encountered SQL Server Error 5171- MDF is Not a Primary Database File [Resolved]

Are you encountering a "SQL Server Error 5171-MDF is not a primary database file" message on the SQL Database server? Don’t worry!!! here you will find all the appropriate solutions to resolve the error in SQL server.

SQL Server is one of the organizations' most widely deployed database servers. The database makes it easy to store and retrieve data from applications running on the same computer or other machines in the same network. Nonetheless, the SQL Server database that ends up corrupted due to some unfavorable conditions. This in turn also affects the database's availability and reliability. The level of corruption suffered by the server depends on the error found by the user and plays a crucial role in assessing the capacity for data recovery from compromised databases.

How “Error 5171 in SQL server” occur?

Due to some causes including viruses and other device infections, failure on shutting down the system, failing to add few files, server crash, failure of hardware and software, corrupted data, etc. these all causes show the occurrence of MS SQL Server error 5171. Then when you attached your .mdf files of the database then this error displays as “MDF is Not a Primary Database File” that creates a SQL Server 5171 error.

Causes

• Corruption of MDF file.
• Inappropriate entries of the registry.
• Infected by Virus.
• Due to Power failure.
• Due to damaged Drivers.

Data is stored as pages within MDF files, each page has a size of 8 KB. The MDF file's first page is referred to as the header page which includes essential database details such as file signature, file length, compatibility, etc.

In the rest of the pages, the actual data is stored. If the SQL Server does not understand the header page or other section, the whole MDF file will not be considered a valid file. This contributes to the 5171 error.

Let us consider two situations and use manual approaches to solve them.

Situation 1: The database corruption in mirrored databases

If you run SQL Server on your system and have some mirrored databases, at the time you use one of the mirrored databases, you need to set it online. You must execute the following commands to do this:
“ALTER DATABASE mydb SET online”

But "Microsoft SQL Server Error 5171" occurs instead of setting the mirrored database. So, to solve this move ahead-

Fix error 5171 in SQL server

1. Initially, set the principal database.
2. By using the “ALTER DATABASE MODIFY FILE” command, modify MDF file data.
3. By clicking on the Stop option, stop the currently running SQL server instance.

1. Copy the MDF and LDF files to a different folder.                                                                         
   
2. At last, again start the SQL Server and then attach MDF and LDF files.

Situation 2: Improper Upgradation of SQL Server

If you use SQL Server 2014 and want to move to SQL Server 2016, another scenario. And, after the successful installation of the new version has been completed, you try to repeatedly attach the MDF file. Therefore, MS SQL Server, this shows Error 5171.

Resolve 5171 error in SQL server-

By running the command "sp attach db" this condition can be eliminated. The SQL error "MDF is not a primary database directory" will be solved.

Professional Solution

If this SQL Server error still exists, you can go to repair the MDF File. Use the SQL Recovery software, that scan and restore MDF file without manual effort in the shortest possible time. This uses an advanced recovery algorithm that can retrieve lost data, removed or inaccessible items from the corrupted MDF file.

Final Thoughts

Here we described in detail the error of SQL Server Error 5171-"MDF is not a primary database File." All strategies have been mentioned above, depending on the circumstances or conditions. When manual methods are not working properly, SQL Recovery Software is another direct choice for getting rid of the mistake.