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Smart Way to Fix Log File Corruption in SQL Server

Alphy Thomas | Modified: 2019-10-15T06:17:35+00:00 | SQL Server|

User Query 1:  “Hello friends! We are dealing with log file corruption in SQL Server. We have tried several manual methods but could not get any effective results. We have completely run out of approaches that can be implemented. Can anyone tell us the solution on how to fix corrupt log file in SQL Server? Help me out experts!”

User Query 2:  “I came across an issue where my log file is corrupted of SQL Server version 2008. My database is not accessible and I am unable to view the database content. I restarted the SQL services but still I am not able to access the database. If anyone knows the solution on how to fix log file corruption in SQL Server and what causes corrupt logs, please help me out.”

Are you facing log file corruption in SQL Server and do not know how to fix them. This post is for you as we will discuss how to fix corrupt log files in SQL Server.

SQL Server is commonly used system to manage relational database. However, SQL Server users bump into several issues where the most severe ones are corruption issues. One such issue is the SQL Server Log File Corruption. In case of corrupted log file, SQL Server database recovery may fail. So it is important to know how to fix log file corruption in SQL Server to avoid these problems.
In this write-up, we will discuss how users can remove corruption from the log files. We will also see what causes log file corruption in SQL Server database.

SQL Server Log File Corruption – Potential Reasons

Log files get corrupted due to various reasons. Here are some of the basic reasons for this corruption.

  • Sudden System Shutdown: If the system is abruptly closed without shutting down the database properly, log files can get damaged.
  • Storage Size Overflow: In case of file size exceeds in log files, it can get corrupt and cause a lot of problems.
  • Problems in Hard Drive: The database and all its components are stored in hard disk drive. In such a situation, the hard-drive gets corrupt, then the log file may get damaged too.
  • Virus / Malware Attack: Like every other component of our system, SQL log file can get affected by different virus and malware. This type of infection can lead to Log file corruption also.
If you are facing corruption issues in MDF & NDF file too, then try one shot solution – SysTools SQL Recovery Software. It easily repairs both primary and secondary database file and export them into SQL Server also. Moreover, one can also download the free version of tool and check out all its features.

 

Download Free SQL Recovery

How to Fix Corrupt Log File in SQL Server?

Step 1: Once you find out that the log files are damaged, you need to look out for the hardware issues that may have caused it. For that, you need to analyze the event logs of Windows system and application. If you identify any hardware problem or disk issues, contact the hardware vendor to fix it immediately because such corruption issues may recur.

Step 2: The next thing you can do is to restore a database backup, but has to be the last known good backup. Here you have to apply three backups sequentially: last complete backup, last differential backup taken after applying complete backup and all transaction log backups taken after applying differential backup. Thus, the database transactional consistency will be retained and the recovery will be done soon.

Step 3: If database restoration from the backup file is not available, database rebuilding has to be done. We need to perform this step because it is not possible to repair corrupt log file. To rebuild, follow these steps:

a. ) First, change the database into emergency mode and then use sp_detach_db command to detach the database. Here is the complete syntax to do this:

b.)  Now, you have to rename or delete the corrupt log files. Then, use this syntax to rebuild and attach the log files:

Step 4: If all these steps fail, then you have to go for the ultimate one and that is to run DBCC CHECKDB command with Repair command. This step is not recommended at all because it may result in data loss. It should only be implemented when users have no other choice. Before running the command, make sure that the database is in emergency mode.

Conclusion

SQL Server log file corruption can take place at any time and it can create a lot of problems to SQL Server users. If users are facing such type of corruption, try to find out the cause of corruption. Afterward, they can follow the steps mentioned in this post. Here, we have discussed simple solutions on how to fix when log file is corrupted in SQL Server.

Frequently Asked Questions –

Q – How to find the whether Log file is corrupted in SQL Server ?

A – If the database recovery process gets failed in SQL Server, then it might be a case of corruption in Log file.

Q – How to rebuild corrupted SQL Server Log file ?

A – First of all, bring the database in Offline mode and change the name of the corrupted Log file associated with it. Now, run the following command.

ALTER DATABASE [original_log_file_name] REBUILD LOG ON
(NAME= logicalname, FILENAME='C:\Program Files\Microsoft SQL Server\MSSQLn.MSSQLSERVER\MSSQL\DATA\file_name.ldf')

Q – How to Fix Corrupted MDF & NDF file?

A – To recover damaged primary & secondary database file, try the SysTools SQL Recovery Software.

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