SQL Server Trace Flag 1118: Boost TempDB Performance & Reduce Contention

In the realm of SQL Server Optimization optimization, small tweaks can yield substantial results, especially when dealing with high-traffic components like TempDB. One such tweak involves the use of Trace Flag 1118, a powerful yet often underutilized tool that can significantly reduce contention and enhance TempDB efficiency. If your SQL Server environment struggles with TempDB bottlenecks, understanding this trace flag could be a game-changer.

TempDB is a critical system database in SQL Server, heavily utilized for temporary objects, sorting operations, and query processing. However, its default page allocation strategy can lead to contention on key system pages, slowing down performance under heavy workloads. Trace Flag 1118 steps in to alter this behavior, ensuring more streamlined allocations and minimizing conflicts, particularly in older SQL Server versions where such optimizations are not built-in.

Whether you’re managing a busy transactional system or a data warehouse with frequent temp table usage, knowing when and how to implement Trace Flag 1118 can make a noticeable difference. This blog post will explore the mechanics of this trace flag, its impact on TempDB performance, and the specific scenarios where it shines. Let’s uncover how this simple setting can help you tackle TempDB contention head-on.

Understanding SQL Server Trace Flag 1118: Enhancing TempDB Performance

When it comes to SQL Server Performance tuning, understanding and using trace flags can provide significant benefits. One particularly valuable trace flag is 1118, which can address contention issues in the TempDB database and improve performance in environments with heavy TempDB usage. Let’s dive into what Trace Flag 1118 does, when to use it, and how it can make a difference.

What Does Trace Flag 1118 Do?

Trace Flag 1118 modifies how SQL Server allocates pages in TempDB. By default, TempDB uses a mixed extent allocation strategy, where the first eight pages allocated to a new object can come from shared extents (extents shared by multiple objects). This can lead to contention on the Global Allocation Map (GAM) and Shared Global Allocation Map (SGAM) pages in TempDB, especially in systems with high concurrency.

When Trace Flag 1118 is enabled:

• All allocations are done using uniform extents. Each extent (8 pages) is allocated to a single object, avoiding shared extents.
• This reduces contention on the GAM and SGAM pages, particularly beneficial for TempDB, where many small temporary objects are frequently created and dropped.

When to Use Trace Flag 1118

Trace Flag 1118 is particularly effective in the following scenarios:

• High TempDB Usage: Environments where TempDB sees frequent object creation, such as temporary tables, table variables, or sorting operations.
• Contention on TempDB Pages: If you observe contention on the GAM or SGAM pages in TempDB (visible in tools like Database Health Monitor or through system views), enabling this trace flag can help.
• SQL Server Versions Prior to 2016: Starting with SQL Server 2016, uniform extent allocation is enabled by default for TempDB, making this trace flag unnecessary in most cases for newer versions.

How to Enable Trace Flag 1118

You can enable Trace Flag 1118 either at the session level (for testing) or globally. However, for TempDB, enabling it globally is the typical approach.

Enable Trace Flag 1118 for Testing (Session Level)

To test the impact of Trace Flag 1118, you can enable it for a single session:

DBCC TRACEON(1118, -1);-- Run your workload here to testDBCC TRACEOFF(1118, -1);    

Enable Trace Flag 1118 Globally

For a permanent configuration, you can add the trace flag to the SQL Server startup parameters:

1. Open SQL Server Configuration Manager.
2. Locate your SQL Server instance, right-click, and choose Properties.
3. Add -T1118 to the Startup Parameters.
4. Restart the SQL Server instance for the change to take effect.

Verify Trace Flag 1118 is Active

After enabling it, you can confirm the trace flag is active:

DBCC TRACESTATUS(1118);    

Impact of Trace Flag 1118 on TempDB

Benefits

• Reduced TempDB Contention: By avoiding shared extents, Trace Flag 1118 minimizes bottlenecks on the allocation pages in TempDB.
• Improved Performance: For workloads that heavily use TempDB, this trace flag can lead to noticeable performance improvements.

Considerations

• SQL Server Version: Starting with SQL Server 2016, uniform extent allocation for TempDB is the default behavior, so this trace flag might not be necessary.
• Global Impact: Enabling Trace Flag 1118 globally affects all databases, not just TempDB. However, its primary benefits are seen in TempDB.

Does Your TempDB Need Attention?

If you’re dealing with TempDB performance issues or contention on allocation pages, Trace Flag 1118 is worth considering. However, Performance Tuning often requires a broader approach. Tools like Database Health Monitor can help identify TempDB bottlenecks and provide recommendations for improvements.

Need Help with SQL Server TempDB Optimization?

At Stedman Solutions, we specialize in SQL Server Performance Tuning and optimization. Whether it’s troubleshooting TempDB contention, configuring trace flags, or improving overall SQL Server efficiency, Our Team of experts is ready to assist. Contact Us for SQL Server Help to us today at our Contact Us page, and let’s resolve your TempDB challenges together!

Summary for Trace Flag 1118

• Trace Flag 1118 as a performance tool for SQL Server TempDB.
• Modification of TempDB page allocation to uniform extents.
• Reduction of contention on GAM and SGAM pages.
• Relevance for high TempDB usage environments.
• Applicability mainly to SQL Server versions prior to 2016.
• Global impact on all databases despite TempDB focus.