Wait Type LATCH_NL

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 uses various wait types to indicate where processes may experience delays. The LATCH_NL wait type occurs when SQL Server threads are waiting for a non-locking latch on a specific resource. Non-locking latches are used for lightweight synchronization, ensuring that threads can safely access shared resources without causing contention. Understanding this wait type can help identify and resolve potential bottlenecks in your SQL Server environment.

What Is the LATCH_NL Wait Type?

The LATCH_NL wait type appears when a thread is waiting to acquire a non-locking latch. These latches are designed to synchronize access to in-memory structures, such as pages in the buffer pool, without locking them exclusively. Non-locking latches are generally very fast, but when they appear frequently or for long durations, it may signal underlying performance issues.

When Does LATCH_NL Appear?

This wait type typically appears in the following scenarios:

• High Concurrency – When many threads attempt to access shared resources simultaneously, leading to contention for non-locking latches.
• Buffer Pool Access – When SQL Server threads need to access or manage in-memory pages in the buffer pool.
• Internal Synchronization – During operations that require coordination between threads to ensure data consistency.
• Limited Resources – When CPU or memory resources are constrained, increasing the time required to acquire or release latches.

Why LATCH_NL Waits Matter

While non-locking latches are designed to be efficient, excessive or prolonged LATCH_NL waits may indicate resource contention or inefficiencies in query execution. Common causes include:

• High Workload – A large number of concurrent queries competing for shared resources can increase latch waits.
• Buffer Pool Contention – Insufficient memory allocated to the buffer pool may lead to frequent latch requests as pages are read and written.
• Inadequate Indexing – Poorly optimized queries that scan large datasets can increase latch activity.
• Resource Bottlenecks – Limited CPU or memory availability can slow latch operations.

How to Address LATCH_NL Waits

If LATCH_NL waits are affecting performance, consider the following strategies:

• Optimize Queries – Ensure queries are efficient and use indexes to minimize the amount of data being processed.
• Increase Memory Allocation – Allocate sufficient memory to the buffer pool to reduce contention for in-memory pages.
• Reduce Concurrency – Adjust workload distribution to avoid too many threads competing for the same resources simultaneously.
• Monitor CPU Utilization – Ensure that the server has adequate CPU resources to handle concurrent latch requests.
• Review Index Strategies – Implement proper indexing to improve query performance and reduce the need for large in-memory operations.

Monitoring LATCH_NL 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, diagnose bottlenecks, and take proactive steps to optimize your SQL Server environment.

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

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Applies to

Related Waits

See Also

• More About LATCH_NL