sql Trace Flag T4135

Posted on 2012-08-29
Last Modified: 2012-09-25
Does anyone have any information on what the following does?

This task has 8 steps.
1.    Open SQL Server Configuration Manager.
2.    From the list of services, select the SQL Server instance.
3.    Right-click and select Properties.
4.    Click the Advanced tab.
  5.    Click the Properties for Startup Parameters and append ;-T4135 to the existing parameters string.
Question by:cheryl9063
    LVL 75

    Expert Comment

    by:Aneesh Retnakaran
    LVL 16

    Expert Comment

    LVL 1

    Author Comment

    Mike, I didnt see anything about the trace flag.. What is it used for and how do you use it?
    LVL 16

    Assisted Solution

    oops! My bad - I posted the wrong URL. This is what I should have posted for you - a listing of the Trace flags. 4135 turns off optimisation, apparently (not that you'd ever guess from the name <grin>)!

    Sorry again - hope this helps some more!
    LVL 3

    Accepted Solution


    The traceflag disables an optimization in the query optimizer. The
    optimization caused the issue described in the KB article when you try to
    insert into a table by selecting from the table itself.

    As turning on the traceflag could result in a perf degradation, you only
    should use it if you run into the issue described in the KB article.

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