Wait Type SQLTRACE_BUFFER_FLUSH

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 wait types to give administrators a detailed look at where delays may occur during processing. The SQLTRACE_BUFFER_FLUSH wait type is tied to SQL Trace, a legacy feature used to capture and log database activity. This wait type appears when SQL Server is writing trace data from memory to disk. Understanding this wait type can help you manage trace sessions and their impact on system performance.

What Is the SQLTRACE_BUFFER_FLUSH Wait Type?

The SQLTRACE_BUFFER_FLUSH wait type occurs when SQL Server’s SQL Trace subsystem is flushing buffered trace data to a file. Trace data is first captured in memory buffers for efficiency and then written to disk periodically. This wait indicates that a process is paused while trace data is being transferred from memory to storage.

This behavior is expected when SQL Trace is running and actively capturing a large volume of events or when the storage system is underperforming.

When Does SQLTRACE_BUFFER_FLUSH Appear?

Common scenarios where SQLTRACE_BUFFER_FLUSH waits occur include:

• Active Trace Sessions – When SQL Trace is capturing high levels of database activity.
• Large Trace Data Volumes – In busy environments where significant amounts of trace data need to be written to disk.
• Slow Disk Performance – When the storage system is not able to handle the write operations efficiently.

Why SQLTRACE_BUFFER_FLUSH Waits Matter

SQLTRACE_BUFFER_FLUSH waits are usually harmless in small doses but can signal inefficiencies if they occur frequently or for extended durations. High wait times may indicate issues such as:

• Excessive Trace Data – Capturing unnecessary events or large amounts of data can lead to frequent flush operations.
• Disk I/O Bottlenecks – Slow or overburdened storage systems may delay data flushing.
• Outdated Trace Usage – Using SQL Trace instead of Extended Events, which is more efficient, can contribute to performance overhead.

How to Address SQLTRACE_BUFFER_FLUSH Waits

If this wait type is affecting performance, consider the following strategies:

• Switch to Extended Events – Replace SQL Trace with Extended Events, a modern and efficient alternative for monitoring and diagnostics.
• Optimize Trace Sessions – Limit the number of events and columns being captured in trace sessions to reduce the volume of data being logged.
• Upgrade Storage Performance – Use faster disks or dedicated storage for trace files to minimize delays during buffer flush operations.
• Reduce Trace Activity – Avoid running trace sessions continuously unless absolutely necessary. Use them selectively for diagnostics and troubleshooting.
• Monitor Trace Overhead – Regularly review the impact of trace sessions using sys.traces and ensure they are configured efficiently.

Monitoring SQLTRACE_BUFFER_FLUSH Waits

To track SQLTRACE_BUFFER_FLUSH waits, use SQL Server’s sys.dm_os_wait_stats to analyze occurrences and durations. Combine this with views like sys.traces to evaluate active trace sessions and their configurations. Tools like Database Health Monitor make it easier to visualize wait types and understand their impact on overall system performance.

Stedman Solutions specializes in helping businesses optimize their SQL Server environments. Whether you need assistance transitioning to Extended Events, improving disk performance, or addressing wait types like SQLTRACE_BUFFER_FLUSH, we can help. Our Database Health Monitor provides valuable insights into wait statistics and system health, and our managed services deliver expert support to keep your SQL Server running efficiently. Contact us today to learn more about how we can support your SQL Server needs.

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Applies to

Related Waits

See Also

• More About SQLTRACE_BUFFER_FLUSH