TempDB Troubles: Identifying and Resolving TempDB Contentions

Author

This blog post was authored by Pinal Dave from SQLAuthority.

Introduction

The tempdb system database is a global resource in Microsoft SQL Server, used for numerous tasks like storing temporary tables and procedure results or as a workspace for sorting and grouping operations. Due to its heavy usage, tempdb can often become a bottleneck, leading to performance issues known as tempdb contentions. In this post, we’ll unravel the common issues surrounding tempdb, discuss native solutions for these contentions, and explore how SQL Diagnostic Manager (SQL DM) provides superior monitoring capabilities to streamline tempdb performance management.

Common TempDB Issues

Tempdb contention, one of the most common issues, occurs when multiple tasks try to allocate pages from tempdb simultaneously. This contention can cause a slowdown in SQL Server performance, affecting all operations that require tempdb. For example, a heavy reporting workload might generate numerous temporary tables simultaneously, leading to tempdb contention and slow report generation.
Another typical issue is the misconfiguration of tempdb, such as improper sizing or incorrect placement of tempdb files. These misconfigurations can lead to inadequate space or disk I/O issues, negatively impacting SQL Server performance. If tempdb fills up due to insufficient space, it can cause operations to fail, leading to application errors and unhappy users.

Built-in SQL Solutions

SQL Server provides native solutions to tempdb contentions and performance problems. While less comprehensive and user-friendly than SQL DM, these tools can provide valuable insights and help you start addressing tempdb issues.

sys.dm_db_file_space_usage

One such tool is the sys.dm_db_file_space_usage dynamic management view (DMV), which provides disk space usage information for tempdb. This DMV can help you identify when tempdb is running out of space and take action before it becomes a problem.
Here’s a sample query:

SELECT SUM(user_object_reserved_page_count) AS user_object_pages,
SUM(internal_object_reserved_page_count) AS internal_object_pages,
SUM(version_store_reserved_page_count) AS version_store_pages,
SUM(mixed_extent_page_count) AS mixed_pages
FROM sys.dm_db_file_space_usage;

This query returns the number of pages used by user objects, internal objects, version store, and mixed extents in tempdb.

Multiple TempDB Data Files

To help alleviate tempdb contention, SQL Server recommends creating multiple tempdb data files. The number of files should generally match the number of logical CPUs, up to eight. Multiple tempdb files can reduce contention by spreading the workload across multiple files, but keeping the files the same size is essential to ensure even usage.
Here’s an example of how to add a tempdb file:

ALTER DATABASE tempdb
ADD FILE (
NAME = tempdev2,
FILENAME = ‘path\to\your\location\tempdb2.ndf’,
SIZE = 512MB,
FILEGROWTH = 256MB);

This command adds a new tempdb file named ‘tempdev2’ with an initial size of 512MB and a growth increment of 256MB. It’s essential to set the initial size large enough to prevent frequent file growths, which can impact performance.

sp_who2 and DBCC SQLPERF(logspace)

Other native tools like sp_who2** and DBCC SQLPERF(logspace) can also be useful for monitoring tempdb. The sp_who2 stored procedure can help identify which sessions are using tempdb, while DBCC SQLPERF(logspace) provides information about the log space usage for all databases, including tempdb.

SQL DM: Outperforming with Superior Monitoring

While SQL Server’s native tools provide valuable insights, SQL DM enhances tempdb performance monitoring by providing a more user-friendly and comprehensive solution.

SQL DM provides real-time tempdb monitoring, presenting an easy-to-understand graphical view of tempdb space and performance information. This feature enables database administrators to spot and diagnose tempdb issues quickly.

Moreover, SQL DM offers customizable alerts for tempdb performance issues. For instance, you can set an alert when tempdb usage reaches a certain threshold. These proactive alerts can help you avoid tempdb contention before it impacts your SQL Server performance.
Furthermore, SQL DM’s tempdb contention monitoring feature provides insights into specific contention types, such as allocation page or catalog contention. This detailed information lets you pinpoint the root cause of tempdb issues and promptly take appropriate action.

Conclusion

Tempdb contentions, if not addressed promptly, can significantly degrade SQL Server performance. While SQL Server’s native tools offer some relief, the superior monitoring capabilities of SQL Diagnostic Manager provide a more comprehensive and user-friendly solution. Real-time tempdb monitoring, customizable alerts, and specific contention monitoring ensure you have all the tools to keep your tempdb and SQL Server performing optimally. This results in smoother database operations, fewer disruptions to business operations, and a better experience for end users.

Experience for yourself how SQL DM can help you identify and resolve tempdb contentions by downloading a free, 14-day trial (a credit card is not required).

About the Author

Pinal Dave is an SQL Server Performance Tuning Expert and independent consultant with over 21 years of hands-on experience. He holds a Masters of Science degree and numerous database certifications. Pinal has authored 13 SQL Server database books and 53 Pluralsight courses. To freely share his knowledge and help others build their expertise, Pinal has also written more than 5,600 database tech articles on his blog at SQLAuthority.