Wait Type LCK_M_UIX_ABORT_BLOCKERS

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.

In SQL Server, wait types are used to identify delays that occur when tasks are waiting for resources or specific events to complete. The LCK_M_UIX_ABORT_BLOCKERS wait type is related to locks and occurs when a process is waiting for an Update-Intent-Exclusive (UIX) lock but is configured to abort blockers that prevent the lock from being acquired. This blog post will explain what this wait type means, when it occurs, and how you can address it in your SQL Server environment.

What Is the LCK_M_UIX_ABORT_BLOCKERS Wait Type?

The LCK_M_UIX_ABORT_BLOCKERS wait type occurs when a transaction is trying to acquire a UIX lock on a resource, but another process is blocking the lock. In these cases, the transaction is configured to abort the blocking process if necessary. This type of lock is typically seen in scenarios involving schema modifications or data updates where SQL Server ensures that only one process can update a specific resource at a time.

The presence of this wait type indicates that SQL Server is managing contention for a resource while attempting to minimize disruption to other transactions.

When Does LCK_M_UIX_ABORT_BLOCKERS Appear?

This wait type can appear in the following scenarios:

• Schema Modifications – When altering a table or index and other transactions are accessing the same resource.
• High-Concurrency Environments – When multiple transactions are competing for resources, leading to contention.
• Deadlock Prevention – When SQL Server uses the abort strategy to handle blocking processes and ensure progress.
• Transactional Updates – During data updates that involve multiple steps requiring fine-grained locks.

Why LCK_M_UIX_ABORT_BLOCKERS Waits Matter

While some occurrences of LCK_M_UIX_ABORT_BLOCKERS waits are expected in high-concurrency environments, frequent or prolonged waits can indicate performance issues or inefficiencies. Common causes include:

• Blocking Transactions – Long-running transactions or poorly optimized queries holding locks can delay other processes.
• Insufficient Indexing – Lack of proper indexing can lead to more locking and contention during updates or schema changes.
• Large Transactions – Operations that touch many rows or resources can cause prolonged locks, increasing contention.
• Poor Lock Granularity – Locks at higher levels (e.g., table-level instead of row-level) can create unnecessary blocking.

How to Address LCK_M_UIX_ABORT_BLOCKERS Waits

If this wait type is causing delays in your SQL Server environment, consider these strategies:

• Optimize Queries – Ensure queries are well-optimized to reduce the number of locks required and the duration of those locks.
• Implement Proper Indexing – Create and maintain indexes to minimize the resources involved in updates or schema modifications.
• Break Up Large Transactions – Divide large transactions into smaller units to reduce contention and the scope of locks.
• Use Appropriate Isolation Levels – Review and adjust transaction isolation levels to balance concurrency and consistency for your workload.
• Monitor Blocking – Use SQL Server tools like sys.dm_tran_locks and sys.dm_exec_requests to identify blocking processes and address the root causes.

Monitoring LCK_M_UIX_ABORT_BLOCKERS Waits

To monitor and analyze this wait type, use SQL Server’s sys.dm_os_wait_stats to track wait statistics. You can also use tools like the Activity Monitor or Extended Events to capture details about blocking processes and lock contention. Tools like Database Health Monitor provide powerful visualizations and analytics for monitoring wait types and identifying performance bottlenecks.

Managing lock contention and resolving wait types like LCK_M_UIX_ABORT_BLOCKERS is essential for ensuring a smooth-running SQL Server environment. Stedman Solutions offers expert managed services and performance tuning to help you optimize your database operations. Our Database Health Monitor tool provides real-time insights into wait statistics and system performance, making it easy to keep your SQL Server environment efficient and reliable. Contact us today to learn how we can support your SQL Server needs!

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Applies to

Related Waits

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• More About LCK_M_UIX_ABORT_BLOCKERS