More Than 15000 Sleeping Sessions In SQL Server 2014

by ADMIN 53 views

Introduction

SQL Server 2014 is a powerful database management system that provides high-performance capabilities. However, like any other complex system, it can be prone to performance issues if not properly configured or maintained. One common issue that can affect the performance of SQL Server 2014 is high CPU utilization. In this article, we will explore the issue of high CPU utilization in SQL Server 2014 and discuss possible causes and solutions.

The Problem of High CPU Utilization

High CPU utilization can be a significant problem in SQL Server 2014, as it can lead to slow query performance, increased latency, and even system crashes. In the scenario described, the CPU utilization is going to 100% regularly, and when checking the system activity using SP_who2, it is showing around 20,000 sessions, most of which are sleeping and utilizing the CPU. This suggests that there is a significant number of processes competing for CPU resources, leading to high CPU utilization.

Possible Causes of High CPU Utilization

There are several possible causes of high CPU utilization in SQL Server 2014. Some of the most common causes include:

  • Resource-intensive queries: Queries that are not optimized or are poorly written can consume a significant amount of CPU resources, leading to high CPU utilization.
  • High concurrency: When multiple users are accessing the database simultaneously, it can lead to high CPU utilization as the system tries to manage the increased load.
  • Deadlocks: Deadlocks occur when two or more processes are blocked, waiting for each other to release resources. This can lead to high CPU utilization as the system tries to resolve the deadlock.
  • System configuration issues: Incorrect system configuration, such as inadequate memory or disk space, can lead to high CPU utilization as the system tries to compensate for the lack of resources.

Analyzing the Issue Using SP_who2

To analyze the issue of high CPU utilization, we can use the SP_who2 system stored procedure. This procedure provides detailed information about the current system activity, including the number of sessions, CPU utilization, and memory usage. By analyzing the output of SP_who2, we can identify the processes that are consuming the most CPU resources and take corrective action to resolve the issue.

Identifying Sleeping Sessions

In the scenario described, most of the sessions are sleeping and utilizing the CPU. This suggests that there is a significant number of processes that are waiting for resources or are in a blocked state. To identify these sleeping sessions, we can use the following query:

SELECT session_id, status, cpu, physical_io, memory_usage
FROM sys.dm_exec_sessions
WHERE status = 'sleeping'

This query will return a list of sessions that are currently sleeping and utilizing the CPU. We can then analyze the output to identify the processes that are consuming the most CPU resources and take corrective action to resolve the issue.

Resolving the Issue

To resolve the issue of high CPU utilization, we need to identify and address the root cause of the problem. Some possible solutions include:

  • Optimizing queries: We can optimize queries to reduce CPU utilization by rewriting them to use more efficient algorithms or by indexing the tables to reduce the number of rows that need to be scanned.
  • Reducing concurrency: We can reduce concurrency by implementing measures such as connection pooling or by limiting the number of concurrent connections.
  • Resolving deadlocks: We can resolve deadlocks by identifying the processes that are causing the deadlock and taking corrective action to resolve the issue.
  • Configuring system resources: We can configure system resources such as memory and disk space to ensure that the system has adequate resources to handle the workload.

Conclusion

High CPU utilization is a common issue in SQL Server 2014 that can lead to slow query performance, increased latency, and even system crashes. By analyzing the issue using SP_who2 and identifying the root cause of the problem, we can take corrective action to resolve the issue. Some possible solutions include optimizing queries, reducing concurrency, resolving deadlocks, and configuring system resources. By following these steps, we can ensure that our SQL Server 2014 system is running efficiently and effectively.

Additional Tips and Best Practices

Here are some additional tips and best practices to help you optimize your SQL Server 2014 system:

  • Monitor system activity: Regularly monitor system activity using tools such as SP_who2 to identify potential issues before they become major problems.
  • Optimize queries: Regularly optimize queries to reduce CPU utilization and improve query performance.
  • Implement connection pooling: Implement connection pooling to reduce the number of concurrent connections and improve system performance.
  • Configure system resources: Configure system resources such as memory and disk space to ensure that the system has adequate resources to handle the workload.
  • Regularly back up the database: Regularly back up the database to ensure that data is safe in case of a system failure.

Q: What are the common causes of high CPU utilization in SQL Server 2014?

A: The common causes of high CPU utilization in SQL Server 2014 include:

  • Resource-intensive queries: Queries that are not optimized or are poorly written can consume a significant amount of CPU resources, leading to high CPU utilization.
  • High concurrency: When multiple users are accessing the database simultaneously, it can lead to high CPU utilization as the system tries to manage the increased load.
  • Deadlocks: Deadlocks occur when two or more processes are blocked, waiting for each other to release resources. This can lead to high CPU utilization as the system tries to resolve the deadlock.
  • System configuration issues: Incorrect system configuration, such as inadequate memory or disk space, can lead to high CPU utilization as the system tries to compensate for the lack of resources.

Q: How can I identify the processes that are consuming the most CPU resources?

A: To identify the processes that are consuming the most CPU resources, you can use the following query:

SELECT session_id, status, cpu, physical_io, memory_usage
FROM sys.dm_exec_sessions
WHERE status = 'sleeping'

This query will return a list of sessions that are currently sleeping and utilizing the CPU. You can then analyze the output to identify the processes that are consuming the most CPU resources.

Q: What is the difference between a sleeping session and a blocked session?

A: A sleeping session is a session that is waiting for resources or is in a blocked state, but is not actively executing a query. A blocked session, on the other hand, is a session that is actively executing a query, but is waiting for a resource to become available.

Q: How can I resolve deadlocks in SQL Server 2014?

A: To resolve deadlocks in SQL Server 2014, you can use the following steps:

  1. Identify the deadlock: Use the following query to identify the deadlock:
SELECT * FROM sys.dm_exec_sessions WHERE session_id IN (SELECT session_id FROM sys.dm_exec_sessions WHERE blocking_session_id IS NOT NULL)
  1. Analyze the deadlock: Analyze the output of the query to identify the processes that are causing the deadlock.
  2. Take corrective action: Take corrective action to resolve the deadlock, such as rewriting the query or indexing the tables.

Q: How can I optimize queries to reduce CPU utilization?

A: To optimize queries to reduce CPU utilization, you can use the following steps:

  1. Rewrite the query: Rewrite the query to use more efficient algorithms or indexing.
  2. Index the tables: Index the tables to reduce the number of rows that need to be scanned.
  3. Use query optimization tools: Use query optimization tools, such as SQL Server Query Optimizer, to identify and optimize queries.

Q: How can I reduce concurrency in SQL Server 2014?

A: To reduce concurrency in SQL Server 2014, you can use the following steps:

  1. Implement connection pooling: Implement connection pooling to reduce the number of concurrent connections.
  2. Limit the number of concurrent connections: Limit the number of concurrent connections to reduce the load on the system.
  3. Use asynchronous queries: Use asynchronous queries to reduce the load on the system.

Q: How can I configure system resources to reduce CPU utilization?

A: To configure system resources to reduce CPU utilization, you can use the following steps:

  1. Increase memory: Increase memory to reduce the load on the CPU.
  2. Increase disk space: Increase disk space to reduce the load on the CPU.
  3. Configure system settings: Configure system settings, such as the number of CPU cores and the amount of memory allocated to each core, to optimize system performance.

By following these steps, you can reduce CPU utilization and improve system performance in SQL Server 2014.