Summary: Use DBCC TRACESTATUS to identify active global trace flags and learn how to enable performance-tuning flags like TF 3226, 6534, and 7745.
Managing Global Trace Flags in SQL Server
Ever wondered which global trace flags are active in your SQL Server environment? Trace flags are frequently used to temporarily set specific server characteristics or to switch off a particular behavior. You can easily discover which flags are currently active using the following command:
-- Check status of all global trace flags
DBCC TRACESTATUS (-1);
This command reveals all currently enabled global trace flags. For instance, you might encounter some common ones used in production environments:
- TF 3226: Suppresses "backup successful" messages in the SQL Server Error Log. This is a must-have for servers with frequent log backups to keep the error log readable.
- TF 6534: Enables native code execution for spatial data types, which can significantly boost performance for GIS-heavy workloads.
- TF 7745: Prevents Query Store data from being written to disk during a failover or shutdown, prioritizing availability over the persistence of the latest runtime stats.
How to Enable a Trace Flag
To enable a specific trace flag globally (the -1 parameter is essential for global scope), use the DBCC TRACEON command:
-- Enable a trace flag globally (e.g., 3226)
DBCC TRACEON (3226, -1);
Note: While DBCC TRACEON enables a flag immediately, it will be lost upon restart. To make a trace flag persistent, you must add it as a Startup Parameter (e.g., -T3226) in the SQL Server Configuration Manager.
For a comprehensive list of all available trace flags, refer to the official Microsoft documentation.
Optimizing your instance? Always test trace flags in a development environment first, as some can significantly change the behavior of the Query Optimizer!
