Wait Type PREEMPTIVE_COM_RELEASEROWS

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 provide valuable insights into where processing delays might be happening. One specific wait type, PREEMPTIVE_COM_RELEASEROWS, occurs when SQL Server waits for an external COM (Component Object Model) operation to complete as it releases resources or rows of data. This wait type can appear in environments where SQL Server interacts with external applications or data sources via COM components. In this post, we’ll break down what PREEMPTIVE_COM_RELEASEROWS means, when it happens, and what it could tell us about your SQL Server environment.

What Is the PREEMPTIVE_COM_RELEASEROWS Wait Type?

The PREEMPTIVE_COM_RELEASEROWS wait type happens when SQL Server is waiting for an external COM operation to release resources or rows of data. COM (Component Object Model) is a Microsoft technology that allows different applications and components to communicate with each other. SQL Server might use COM objects to perform tasks such as retrieving or releasing data from linked servers or using OLE DB providers to connect to external sources.

When SQL Server interacts with these external systems, it sometimes needs to release rows of data it has retrieved or processed. If SQL Server is waiting for the external system to complete this release operation, it goes into preemptive mode—meaning that SQL Server hands control to the operating system and waits for the external task to finish. This is why this wait type is called PREEMPTIVE_COM_RELEASEROWS.

When Does PREEMPTIVE_COM_RELEASEROWS Appear?

The PREEMPTIVE_COM_RELEASEROWS wait type generally appears in environments where SQL Server interacts with external data sources or applications through COM components. Some common scenarios include:

• Linked Server Connections – When SQL Server retrieves or releases data from a linked server (such as another SQL Server instance or an external database), it may experience PREEMPTIVE_COM_RELEASEROWS waits if the linked server is slow to respond.
• OLE DB Providers – SQL Server may use OLE DB providers to connect to non-SQL Server data sources. If SQL Server is waiting for the provider to release data rows, it can lead to PREEMPTIVE_COM_RELEASEROWS waits.
• External Data Source Operations – Any data operation that relies on COM components to connect to external data sources, such as some BI tools or ETL processes, may produce this wait type as SQL Server waits on the external system to complete its tasks.

While some PREEMPTIVE_COM_RELEASEROWS waits are normal in SQL Server environments with external dependencies, frequent or prolonged waits may indicate potential issues with the external system or connection.

Why PREEMPTIVE_COM_RELEASEROWS Waits Matter

Although occasional PREEMPTIVE_COM_RELEASEROWS waits are expected when SQL Server interacts with external data sources, prolonged or frequent waits can slow down SQL Server performance. High wait times in this category can mean that SQL Server is spending too much time waiting on the external system to release data, which can delay other queries and processes.

Common causes for high PREEMPTIVE_COM_RELEASEROWS waits include:

• Slow External Systems – If the external system or data source that SQL Server is interacting with is slow, it can cause longer waits.
• Network Latency – When data is being accessed over a network, high latency can lead to increased wait times for SQL Server.
• Resource Constraints on External Components – Limited resources, such as CPU or memory on the external system, can cause delays as SQL Server waits for rows to be released.

How to Address PREEMPTIVE_COM_RELEASEROWS Waits

If you are seeing frequent or prolonged PREEMPTIVE_COM_RELEASEROWS waits, here are a few strategies to improve performance:

• Optimize Linked Server Usage – Limit the frequency of linked server queries, or optimize queries to reduce dependency on external data sources.
• Monitor Network Performance – If data is accessed over a network, ensure that network latency is minimized for better data transfer performance.
• Increase Resources for External Systems – Ensure that the external system has adequate CPU, memory, and disk resources to process and release data efficiently.
• Limit OLE DB or COM Component Usage – If possible, minimize the use of OLE DB or COM components for data access to reduce dependency on external COM operations.

Conclusion

The PREEMPTIVE_COM_RELEASEROWS wait type in SQL Server occurs when the server is waiting for an external COM operation to release rows of data. Although some waits of this type are normal, frequent or high wait times can indicate issues with external systems or network performance. By optimizing linked server usage, monitoring network performance, and ensuring that external systems have adequate resources, you can help reduce PREEMPTIVE_COM_RELEASEROWS waits and improve SQL Server efficiency.

For expert SQL Server performance tuning and help with optimizing external integrations, Stedman Solutions offers managed services designed to keep your SQL Server environment running smoothly and efficiently.

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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_COM_RELEASEROWS