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How to repair corrupt SQL Database?

Avatar Ruchika Srichand Updated On - 15 Jun 2020

Repairing corrupt SQL Server Database can be a tedious task if you don’t know the right technique. There is manual technique available to repair corrupt SQL database but a professional and authentic third-party software is always the best approach to do it. There are plenty of software available online for the purpose but finding the best one is again a big task. Before knowing about the SQL recovery solutions, you should know about SQL Server and reasons of its corruption.

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What is SQL Server?

SQL Server is a database management system largely used for storing and retrieving data by other applications. Developed by Microsoft, SQL Server uses three types of files to store and manage data – Primary Files (MDF), Secondary Files (NDF) and Log Files (LDF).

  • Primary SQL Server database files have .MDF extension. Each database has one primary file and it store user data and objects including Indexes, Columns, Views, Functions, Values, Tables, Keys, Stored Procedures, Triggers, Default Values, etc. MDF files also store the startup information for the database.
  • Secondary files are optional and have .NDF extension. You can create unlimited number of NDF files as per your requirement. Commonly used to spread data across multiple disks, NDF files can be used to store user data as well.
  • Log files are basically the backup files of SQL Server database. They are used to restore the database in case of corruption. Log files have .LDF extension and store log information. Every database has at least one log file.

Reasons of SQL Database corruption

SQL Server database can be corrupted due to various reasons. MDF files are the primary database files holding the user data and its corruption can corrupt the entire database. There are multiple reasons that can cause MDF corruption such as:

  • Storage media corruption where MDF files are stored
  • Storing SQL database in compressed folders
  • Changes in SQL Server account
  • Accidental data deletion
  • File header corruption
  • Bugs in disk drivers
  • Network failure when database is in working condition
  • Hard disk failure, sudden power failure, unexpected system shutdown, virus attacks are some of the reasons that can cause MDF corruption.

In case of MDF corruption, SQL database becomes inaccessible. If you try to access the corrupt database, you might get different error messages. Some most common error messages are:

  • Corruption on data pages
  • Msg 823 error in SQL Server / Msg 824 in SQL Server / Msg 825 (read retry) in SQL Server
  • Error 9004 in SQL Server
  • SQL Server Table Corruption Error
  • Metadata Corruption Error
  • SQL Server Page Level Corruption

And, there are several other error messages you might get while trying to open a corrupt SQL database. If you’re a database administrator, you need to act immediately to prevent any kind of data loss. Read on to know the solutions to restore corrupt SQL database.

How to detect the corruption in SQL Database?

The main job of the Database Administrator is to keep the database highly secure and available. When there is corruption in database files, then sometimes it may not show any symptoms of error but the data remains unavailable. That’s why the administrator should employ some methods that check the health of the database to find any errors or corruption.

  1. Run the database backup along with CHECKSUM
  2. When the Administrator is running the database backup process, then the CHECKSUM command should also be included with the backup command. The CHECKSUM command will check the database for any corruption and stop the backup process if it finds any.

    BACKUP DATABASE XYZ
    TO DISK = ‘E:\Database Backup\XYZ.bak’
    WITH CHECKSUM;

    Run the command and see the results.

  3. Run the DBDC CHECKDB command
  4. DBDC is the command to run the routine checkup of the database and it detects several issues affecting the the database.

    DBCC CHECKDB ;

    The command will check the physical and logical integrity of all the database objects like tables, triggers, relationships, dependencies, and if it finds any problem, then it will be shown in the result with the error message. The error message will clearly show the details like why it showed the error and stopped the process from finishing.

How to repair corrupt SQL Database?

There are few manual solutions to repair corrupt SQL database but they do not guarantee the database recovery.

You can use the log files (NDF) of SQL Server to restore the database. However, log files are not sufficient enough to recover the database in many corruption cases. Sometimes, backup files also get corrupted if the corruption is severe.

Another way to repair the corrupt SQL database is using the database console commands i.e. DBCC CHECKDB and DBCC DEBREPAIR. They can be useful to fix minor SQL database corruption issues but they aren’t very much efficient though for all corruption cases. And, performing database console commands require certain technical knowledge which might be confusing for non-technical users.

Thus, using an authentic third-party software is the best way to repair and recover corrupt or damaged SQL Database. Kernel for SQL Database Recovery is the best software available to fix database corruption errors.

Kernel for SQL Database Recovery

Kernel for SQL Database Recovery is probably the best software to deal with all kinds of SQL database corruption issues effectively. The software is extraordinarily programmed to fix all minor and major MDF (primary database files of SQL Server) file corruption issues with accuracy. Ensuring effortless database recovery in almost no time without making any data loss, the software offers some really high-end features. In fact, the good and most remarkable aspect about the tool is its ability to restore all SQL database objects including Tables, Columns, Indexes, Functions, Values, Keys, Views, Rules, Triggers, Stored Procedures, Checks, Default Values, User data types etc. Adding to that, it even provides complete support to restore multiple MDF files at the same time. No matter whether the size of database is big or too big, the tool easily repair MDF file of any size.

Follow the below-mentioned steps to recover from corrupt SQL database:

Step 1: Start Kernel for SQL Database Recovery software and click the Browse button to select database which you want to repair and select the SQL database version.

select the SQL database version

There are two recovery mode which you can choose as per severity of corruption in database file –

Standard scan – A standard scan is useful for minor corruption.

Advanced scan – Use advanced scan in case standard scan is not able to remove the error or the database is showing “Out of Memory” message.

Step 2: After the scanning process, the software displays all the recovered database objects for preview before saving as shown below.

preview recovered database

Step 3: Hit on the Save button and choose one of the saving modes as desired and click OK.

choose saving modes

Step 4: Finally, your corrupt SQL database is repaired and saved successfully.

successfully recover data

Moreover, the tool has got SQL Server mode and Batch File mode to save the recovered objects directly in SQL Server and Batch file of recovered database respectively. And, the best part is its availability in free trial version. The trial version of Kernel for SQL Database Recovery tool is absolutely free. Trial version can recover the database objects but doesn’t allow saving, and so to overcome the limitation, you would require to buy the licensed version.

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Conclusion:

In this blog, we have discussed all about SQL database and its corruption. In the first part we discussed what SQL server is, and how an SQL database may become corrupt. We also tried to mention all the error notifications that a user may face while facing the corruption. This may help the user to identify corruption from the next time. We have also mentioned the ways with which you can easily detect the database corruption. Lastly, we discussed the solutions with which you can fix the SQL database corruption. We mentioned the best, the quickest and the safest way to deal with SQL database corruption – Kernel for SQL Database Recovery tool. The tool has a user-friendly interface and comes with a trial version. Hope this blog was helpful. Let us know in comments about your queries and concerns.

TechNet Moderator Reviews on Kernel for SQL Database Recovery