seniorT-SQL
What is SQL Server execution context switching overhead?
Updated May 17, 2026
Short answer
Execution context switching occurs when SQL Server changes security or execution identity mid-query.
Deep explanation
Context switching happens with EXECUTE AS, module impersonation, or cross-database ownership chaining. Each switch introduces overhead due to security token validation and permission recalculation. Excessive switching in loops or functions can degrade performance significantly.
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