SQL Server Wait Types: Key Issues and Troubleshooting ( Part 13 of 16 )

SQL Server Wait Types: Key Issues and Troubleshooting

Summary

Managing wait types is critical for optimizing SQL Server performance. Here’s a detailed look at some notable wait types and how to address them:

1. ASYNC_NETWORK_IO Waits :

- Occur when SQL Server waits for a client application to consume data.

- May indicate network throughput inefficiencies or client applications processing data row by row.

- Troubleshooting : Review network topology and client implementations.

2. THREADPOOL Waits :

- Signify worker thread starvation, where SQL Server lacks enough workers to handle client requests, rendering it unresponsive.

- Common triggers: long blocking chains, insufficient memory, and heavy, often nonoptimized load.

- Troubleshooting : Investigate the root causes and use a Dedicated Admin Connection (DAC) for immediate intervention. Ensure DAC remote access is enabled during server provisioning.

3. BACKUPIO and BACKUPBUFFER Waits :

- Occur when SQL Server experiences insufficient throughput for reading from or writing to backup files.

- Troubleshooting : Analyze and optimize the backup process and infrastructure.

4. Preemptive Waits :

- Happen when SQL Server calls external functions using a preemptive execution model.

- Most are generally ignorable, but pay attention to authentication-related, OLEDB, and I/O-related preemptive waits.

- Troubleshooting : Address specific external function issues as necessary.

In the next chapter, we’ll shift focus to detecting inefficiencies in database schema and indexing.

Troubleshooting Checklist

1. Review Network Topology and Client Implementation :

- When encountering a large number of ASYNC_NETWORK_IO waits, examine the network and client-side data consumption patterns.

2. Investigate THREADPOOL Waits :

- Look into potential causes like long blocking chains, memory issues, and nonoptimized load. Ensure sufficient worker threads are available.

3. Review Backup Strategies :

- Analyze your disaster recovery and backup strategies, tuning the backup process to address BACKUPIO and BACKUPBUFFER waits.

4. Analyze Columnstore Indexes :

- Check the size of delta stores and the state of rowgroups if you encounter HTBUILD or batch-mode execution-related waits.

5. Troubleshoot Preemptive and OLEDB Waits :

- If these waits are prevalent, investigate and address the underlying issues.

By understanding and addressing these wait types, you can significantly improve your SQL Server’s performance and reliability. Stay tuned for the next chapter, where we’ll delve into detecting and optimizing inefficiencies in database schema and indexing. Happy troubleshooting!