* SQL Server provides parallel queries to optimize query execution and index operations for computers that have m ore than one microprocessor (CPU) . Because SQL Server can perform a query or index operation in parallel by using several operating system threads, the operation can be completed quickly and efficiently. * During query optimization, SQL Server looks for queries or index operations that might benefit from parallel execution. * For these queries, SQL Server inserts exchange operators into the query execution plan to prepare the query for parallel execution . * An exchange operator is an operator in a query execution plan that provides process management, data redistribution, and flow control . The exchange operator includes the Distribute Streams , Repartition Streams , and Gather Streams logical operators as subtypes, one or more of which can appear in the Show plan output of a query plan for a parallel query. * After exchange operators are inserted, the resul