How To Fix MS SQL Server Error 18456? Causes And Solutions

What Causes Microsoft SQL Server Error 18456?

SQL Server error 18456 is an error of authentication failure, which means that a login has failed. This error may be caused by several factors, including:

• The most frequent cause is typing an incorrect password or username.
• If SQL Server is configured to Windows Authentication Mode only, it will reject connections using SQL Server authentication. 
• The administrator may have disabled the login account. 
• The account could also be locked due to repeated failed login attempts.
• Login might lack the necessary permission to read from the database.
• A SQL Server instance can be terminated, blocking any attempts to login.
• Database corruption occasionally leads to authentication failure.
• Incorrect server configurations or network setup could prevent login.

SQL Server Error 18456 generally occurs due to authentication-related problems. Finding out the precise cause by examining the error log and fixing the problem will normally resolve the issue.

What is Error 18456 of SQL Server?

SQL Server Error 18456 is an authentication failure error that arises when a login attempt to the SQL Server instance fails. The complete error message typically appears as:

Login failed for user ‘username’. (Microsoft SQL Server, Error: 18456)

This error means that SQL Server was not able to verify the user and therefore denied database access. It does not specify the exact reason, but the cause can be related to various authentication issues.

How Do I Fix Error 18456 in SQL Server?

To correct Error 18456 in SQL Server, which generally points to a failure in authentication, you’ll have to troubleshoot the root cause. Below are the standard steps to fix the problem:

1. Verify Credentials (Username/Password)

The most frequent source of error 18456 is the use of incorrect login information, including a wrong username or password.

Solution:

1. Always double-check your username and password you used to log in.
2. Make sure the password is typed in properly, including case sensitivity, since SQL Server passwords are case-sensitive.
3. If you are not sure, reset the login password. To reset the password:

ALTER LOGIN [username] WITH PASSWORD = ‘newpassword’;

Note: Make sure you are using the right account type (SQL Server or Windows Authentication).

2. Check SQL Server Authentication Mode

SQL Server can be configured to Windows Authentication Mode (Windows logins only) or Mixed Mode (both SQL Server and Windows logins). When SQL Server is in Windows authentication mode, SQL Server login credentials (SQL Server authentication) will fail, and Error 18456 will be generated.

Solution:

1. First, download and open SQL Server Management Studio (SSMS).
2. After that, connect SSMS to the valid account server.
3. Next, right-click the server in Object Explorer > Properties.
4. Under the properties option, go to the Security page.
5. Here, set server authentication to SQL Server and Windows authentication mode (mixed mode).
6. Re-start the SQL Server service to effect the change.
7. If doubtful, follow this query to determine the authentication mode:

SELECT SERVERPROPERTY(‘ProductLevel’);

3. Check Account Status

Sometimes, the login account may become disabled, hindering login access.

Solution:

1. You may verify the login status through the following SQL command:

SELECT name, is_disabledFROM sys.sql_loginsWHERE name = ‘username’;

2. If the account is disabled, you can enable it by running:

ALTER LOGIN [username] ENABLE;

3. Confirm that the account status is correctly set in SQL Server.

4. Check for Account Lockout

Accounts may become locked if there are repeated failed login attempts. This is a security feature to prevent brute force attacks.

Solution:

1. To verify whether the account is locked, examine the SQL Server logs for login attempts or account lockout-related errors.
2. If the account is locked, you can unlock it by executing:

ALTER LOGIN [username] WITH PASSWORD = ‘newpassword’;

3. Make sure that the number of permitted login attempts is sufficient and well set to prevent lockouts.

5. Ensure Correct Permissions

A login can lack the appropriate permissions to use the particular database, and that can cause Error 18456.

Solution:

1. Verify whether the user possesses the necessary permissions to connect to the database and the server.
2. Assign the user to the proper roles through:

EXEC sp_addrolemember ‘db_owner’, ‘username’;

3. Verify that the login is mapped to the database. Map the login to the database manually if necessary:

USE [database_name];CREATE USER [username] FOR LOGIN [username];

SQL Server Error 18456 can be due to various reasons, which most often involve authentication, permissions, or server configurations. By thoroughly checking credentials, authentication modes, account status, permissions, and SQL Server settings, you may fix the error. Always investigate error logs for further information, and correct any existing server or database issues to facilitate a smooth workflow.

6. Automated Software to Fix MS SQL Server Error 18456

MS SQL Error 18456 usually indicates an authentication problem due to incorrect login credentials. However, it may also signal MDF file corruption. The MDF file is essential for storing data, tables, and queries. To fix MDF file corruption, use a reliable SQL Database Recovery Tool. These tools efficiently repair and recover corrupted MDF files. They offer a user-friendly interface for all technical skill levels. Additionally, they maintain data integrity and preserve the database hierarchy. This ensures no data is lost during the repair, allowing quick restoration of your database. Besides this, the software also helps you recover MDF file data in case you repair SQL Database 2008.

Simple Steps to Fix Error 18456

1. First, download and run the SQL Database Recovery Tool on your PC.
2. After that, choose the Open option to pick up the corrupted MDF files.
3. Next, browse them from your local storage.
4. Later, select the recovery mode based on your level of corruption.
5. Now, preview the corruption of the MDF file.
6. Next, for SQL Server Authentication, enter the account credentials and verify the database connectivity.
7. At last, tap on the OK button to fix error 18456.

The steps mentioned above don’t need tech-savvy to make them simple. In addition, you can save time and effort using this software.

Conclusion

In summary, resolving MS SQL Server Error 18456 is a critical task that needs attention. This blog has given an efficient solution to fix MS SQL server error 18456 with no downtime. There is no guarantee that the manual method can certainly recover your SQL data. Therefore, it is not suitable for individuals. But with the assistance of trustworthy utilities, users can prevent data loss and maintain database integrity.