The query processor in SQL Server 2012 includes parallel query processing—an execution strategy that can improve the performance of complex queries on computers with more than one processor.
SQL Server inserts exchange operators into each parallel query to build and manage the query execution plan. The exchange operator is responsible for providing process management, data redistribution, and flow control. The exchange operators are displayed in the query plans as the
Repartition Streams, and
Gather Streams logical operators. One or more of these operators can appear in the execution plan output of a query plan for a parallel query.
Whereas a parallel query execution plan can use more than one thread, ...