SQL Server Wait Stats Tool

What are wait stats in SQL Server?

SQL Server wait stats are an integral component of your SQL Server management. The job of wait statistics is to show your server’s threads and their status in the scheduler and how many threads at a given time are waiting in the waiter list. With a complete understanding of your thread inventory, you can identify trends in wait times and detect sources of common issues with resource deficiency. In short, SQL Server wait stats show you different measurements of your SQL Server performance—which threads are waiting, how long they’re waiting, and what wait type is associated with each thread.

SQL Server management tools can associate specific threads with their wait types. Once you identify wait stats and wait type, you can pinpoint the root cause of downtime with maximum precision.

For IT admins, wait statistics in SQL Server management offer an effective way to identify the root cause of downtime for troubleshooting. As any admin knows, application downtime is a costly inefficiency for your client’s enterprise. By using current and historical wait stats in SQL Server, you can troubleshoot bottlenecks and minimize downtime, saving you time, money, and hassle.

How to check wait stats in SQL Server?

To analyze wait stats, SQL Server management requires more than only an understanding of your current SQL Server waits. Even though autonomous resources offer insight into your SQL Server wait resources, effective troubleshooting means you understand overall trends—not merely current wait types and wait times.

There are plenty of wait types SQL Server tools consistently get wrong, like CXPACKET wait types. Due to the incomplete nature of traditional SQL Server monitoring tools, sophisticated SQL Server wait stats analysis requires a more comprehensive understanding of SQL Server client statistics.

The optimal approach to SQL Server performance troubleshooting is a tried-and-true methodology utilizing wait statistics, performance monitor queues, and other relevant performance metrics.

SolarWinds SQL Sentry provides a tool for identifying wait stats resource consumption, combined with historical trends. Intuitive data visualization and custom intervals help you streamline your analytics and gain a bird’s-eye view into SQL Server wait time trends.

What are wait types in SQL Server?

Wait types help you determine a more specific bottleneck on a SQL Server—such as schema locking issues, plan cache memory pressures, or backup I/O problems—instead of simply generic locking, memory, or I/O issues you might identify through other methods. The promise of wait stat analysis is—you now have an excellent way to quickly determine where the strongest pressures are building up on specific resources within SQL Server.

When your application uses resources from the SQL Server relational database, SQL Server executes requests using threads. A thread executes code to communicate with the SQL Server on a tight schedule. If these threads are unable to execute their required commands due to a lack of server resources, they must wait to complete the query until they have enough resources to continue.

Within your SQL Server, a tool called a scheduler serves as the mechanism for moving individual threads through the SQL Server to retrieve data and complete a query. The scheduler serves several important purposes within your SQL Server, with each thread’s major life cycle occurring within your schedule. The scheduler contains the SQL Server processor, which contains threads before and during their execution of the desired code.

Before a thread executes code, the scheduler houses all the threads waiting to execute their respective codes. This runnable queue isn’t an inherent source of downtime since the threads typically move through the queue at the correct speed determined by the scheduler.

There are plenty of cases in which threads are unable to move through the runnable query on time due to a lack of resources. When a thread can’t execute code as scheduled because of insufficient resource availability, it gets stuck on the waiter list.

The scheduler typically contains a constant backup of threads on the waiter list unable to move forward for various reasons. For optimal wait statistics, SQL Server management tools can help identify the causative relationship between threads in your waiter list, and the resource deficiencies causing the bottleneck.

Each resource deficiency potentially causing a wait time is called a wait type. In short, a wait type is the reason why your thread is unable to move forward through the scheduler and properly execute its code.

There are hundreds of wait types, each of which provides unique insight into the causes of bottlenecks. Some common wait types include:

• PAGEIOLACH_EX waits indicate buffering, along with other PAGEIOLACH_* wait types like PAGEIOLACH_SH.
• OLEDB waits indicate a thread is waiting for a response from the OLE DB before it can continue.
• CXPACKET waits indicate your thread has been slowed due to parallel queries.
• And many more.

In a wait type-based SQL Server wait stats tool, like SQL Sentry, your wait type library provides a complete record of wait types for fast and easy identification. Once your SQL Server analytics tool has identified the wait type of a thread, you can understand which resources are limited, and you can troubleshoot the bottleneck.

How to monitor SQL Server wait stats in SQL Sentry

With a user-friendly format, SolarWinds SQL Sentry provides a highly intuitive way to visualize SQL wait time stats without combing through mountains of code to get there. Simply log onto your SQL Sentry dashboard, view wait stats for specific threads or wait types, and identify where you need to troubleshoot issues.

Other key features of SQL Sentry include:

• Baseline detection: SQL Sentry allows you to view the baseline wait times of different threads within the runnable queue so you can distinguish planned from unplanned wait times.
• Actionable details: With SQL Sentry, you can understand the factors which might influence SQL Server wait times outside of SQL Server itself. Actionable details provide essential background information for potential troubleshooting.
• Parallelism: To identify wait times for parallel threads, SQL Sentry includes SQL Server CXPACKET analytics. SQL Server CXPACKET tools help you understand the wait times of each parallel thread and not over account for wait times due to parallelism.
• And more.

On top of high-precision SQL Server wait time analytics, SQL Sentry also provides customizable graphs, charts, and displays for a more effective solution to SQL Server analysis. With custom features, high-precision server analytics, and an intuitive UI, SolarWinds SQL Sentry helps you identify SQL Server wait times for minimum downtime and maximum resource capacity.