Wait Type PREEMPTIVE_OS_LOGONUSER

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a "wait" and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.

SQL Server wait types provide valuable insights into where processes encounter delays. The PREEMPTIVE_OS_LOGONUSER wait type occurs when SQL Server is executing an external operation related to user authentication. Specifically, it happens when SQL Server calls the Windows API to authenticate a user login. Understanding this wait type is important for troubleshooting login-related delays and ensuring efficient user authentication.

What Is the PREEMPTIVE_OS_LOGONUSER Wait Type?

The PREEMPTIVE_OS_LOGONUSER wait type occurs when SQL Server relinquishes its internal scheduling to let the operating system handle a logon user request. This process is preemptive because SQL Server waits for the external Windows API to complete the operation before proceeding. If this wait type appears frequently or for extended durations, it may signal underlying issues with authentication or the operating system.

When Does PREEMPTIVE_OS_LOGONUSER Appear?

This wait type is typically encountered in the following scenarios:

• User Login Authentication – When SQL Server authenticates a user via Windows Authentication.
• Linked Server Connections – When a query involves authentication to a linked server using Windows credentials.
• High Login Activity – In systems with many simultaneous user logins, increasing authentication load.
• Domain Controller Issues – When the domain controller or Active Directory is slow to respond to authentication requests.

Why PREEMPTIVE_OS_LOGONUSER Waits Matter

Some PREEMPTIVE_OS_LOGONUSER waits are expected in environments using Windows Authentication. However, excessive or prolonged waits may indicate performance bottlenecks. Common causes include:

• Slow Domain Controller Response – Delays in communication with the domain controller can increase authentication time.
• High Authentication Load – A large number of concurrent authentication requests can overwhelm the system.
• Network Latency – Slow network connections between SQL Server and the domain controller can cause delays.
• Misconfigured Linked Servers – Poorly configured linked server settings can lead to unnecessary authentication calls.

How to Address PREEMPTIVE_OS_LOGONUSER Waits

To reduce the impact of this wait type, consider the following strategies:

• Optimize Domain Controller Performance – Ensure that domain controllers are adequately resourced and responsive to authentication requests.
• Reduce Authentication Overhead – Use connection pooling to minimize the number of authentication requests in high-traffic environments.
• Improve Network Connectivity – Ensure a reliable and low-latency network connection between SQL Server and the domain controller.
• Check Linked Server Configurations – Validate that linked server connections are configured correctly to avoid unnecessary authentication operations.
• Enable Kerberos Authentication – Use Kerberos for more efficient authentication in environments requiring secure logins.

Monitoring PREEMPTIVE_OS_LOGONUSER Waits

To track and analyze this wait type over time, use the Historic Waits Monitoring feature in Database Health Monitor. This tool provides detailed insights into wait statistics, helping you identify trends and diagnose login-related bottlenecks. Regular monitoring allows you to proactively address authentication delays and maintain system performance.

Stedman Solutions specializes in SQL Server performance tuning and troubleshooting. Whether you’re experiencing PREEMPTIVE_OS_LOGONUSER waits or other SQL Server challenges, our Database Health Monitor provides powerful insights, and our managed services deliver expert support to keep your SQL Server environment running smoothly. Contact us today to learn how we can help improve your SQL Server performance and reliability.

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Applies to

• SQL Server 2016
• SQL Server 2017
• SQL Server 2019
• SQL Server 2022

Related Waits

See Also

• More About PREEMPTIVE_OS_LOGONUSER