I've noticed a strange behaviour of SQL Server 2008 r2 express:
usually my query execution time is ~650ms, but if I open Management Studio and run any simple query (for example
SELECT * FROM Something), the execution time becomes ~40ms. If I close management studio this value returns to normal ~650ms
And no matter where the query was executed: from Management Studio or my application (it uses ADO.Net)
ARITHABORT setting has no effect
Why is this happening?