Global Trace Flags Are Global

Kendra Little points out that when you turn a trace flag on globally, it cannot be off for individual sessions:

In SQL Server 2016, you can now enable the very same optimizer hotfixes controlled by Trace Flag 4199 at the database scope by using ALTER DATABASE SCOPED CONFIGURATION SET QUERY_OPTIMIZER_HOTFIXES=ON.

If you have the setting configured at the database level, it’s much easier to test what would happen if the setting was NOT enabled, because you can compile your query from a different database.

Interesting results.  Check it out.

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Finding Trace Flag Usage With dbachecks

Rob Sewell points out an addition to dbachecks: This will show you the UniqueTag which will enable you to run only that check if you wish AllTags which shows which tags will include that check Config will show you which configuration items can be set for this check The trace flag checks require the app.sqlinstance […]

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Collecting Plan Metrics With Trace Flag 7412

Grant Fritchey shows a lightweight way of capturing plan metrics: I place a lot of emphasis on capturing actual execution plans because of the runtime metrics, but with Trace Flag 7412, we don’t need the plan. This is great news, because capturing execution plans, even using extended events, is an expensive proposition. However, using either […]

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