Wait Type LCK_M_RX_S_LOW_PRIORITY

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 locks to manage concurrency and ensure data consistency during transactions. When tasks are executed with lower priority, specific wait types such as LCK_M_RX_S_LOW_PRIORITY can occur. Understanding this wait type helps you diagnose and address performance issues, improving the efficiency of your SQL Server environment.

What is LCK_M_RX_S_LOW_PRIORITY?

The LCK_M_RX_S_LOW_PRIORITY wait type occurs when a session is waiting to acquire a Range-Exclusive Shared (RX_S) lock in low-priority mode. This lock is used during read operations on a range of data, allowing shared access for reads while preventing any modifications. In low-priority mode, the session waits until higher-priority locks are released before proceeding.

In simpler terms, this wait type means SQL Server is pausing a low-priority range-based read operation to avoid disrupting higher-priority tasks. While some waiting is expected, frequent or prolonged waits may indicate contention or inefficiencies in your workload.

Why Does LCK_M_RX_S_LOW_PRIORITY Happen?

Several factors can contribute to LCK_M_RX_S_LOW_PRIORITY waits, including:

• Long-running transactions holding higher-priority locks on the resource.
• High contention for specific tables, rows, or partitions being accessed.
• Inefficient queries or missing indexes causing longer execution times and lock durations.
• Concurrency challenges during peak usage, leading to overlapping transactions.
• Heavy workloads involving frequent range-based reads and writes to the same data.

Identifying and addressing these factors can help reduce contention and improve overall database performance.

How to Monitor LCK_M_RX_S_LOW_PRIORITY Waits

Monitoring LCK_M_RX_S_LOW_PRIORITY waits is critical for diagnosing their causes and minimizing their impact. The Database Health Monitor is an excellent tool for tracking this wait type. Its Historic Waits Monitoring feature provides detailed insights into when and how often these waits occur, their duration, and their effect on overall system performance.

Using Database Health Monitor, you can detect patterns in these waits and determine whether they stem from inefficient queries, blocking chains, or resource contention. This data allows you to take targeted corrective actions to optimize your SQL Server environment.

What Can You Do About LCK_M_RX_S_LOW_PRIORITY Waits?

If you notice frequent or prolonged LCK_M_RX_S_LOW_PRIORITY waits, consider these strategies:

• Analyze and resolve blocking chains using tools like Extended Events or Activity Monitor to identify and address conflicting transactions.
• Optimize queries to reduce execution time and minimize lock durations.
• Ensure indexes are properly designed to improve query efficiency and reduce contention.
• Partition large tables to limit the scope of range-based locks and reduce conflicts.
• Break long-running read operations into smaller tasks to lower blocking potential.
• Adjust transaction isolation levels to balance concurrency and data consistency requirements for your workload.
• Schedule low-priority range-based tasks, such as scans or reports, during off-peak hours to avoid conflicts with high-priority operations.

Implementing these steps can help you reduce contention and maintain efficient operations in your SQL Server environment.

Why Use Database Health Monitor?

The Database Health Monitor is a powerful tool for tracking SQL Server wait types, including LCK_M_RX_S_LOW_PRIORITY. Its Historic Waits Monitoring feature provides actionable insights into wait trends, helping you identify and resolve performance bottlenecks. With Database Health Monitor, you can ensure your SQL Server environment runs smoothly and efficiently.

Start using Database Health Monitor today to monitor and optimize your SQL Server’s performance, ensuring reliable and effective database operations!

Watch on YouTube

Find out more about our SQL Server Managed Services

Applies to

Related Waits

See Also

• More About LCK_M_RX_S_LOW_PRIORITY