Degree of Parallelism & Max Degree of Parallelism - SQL Server

In SQL Server 2022, the degree of parallelism (DOP) and the max degree of parallelism (MDOP) continue to play an important role in optimizing query performance, but there are some changes and enhancements to these features that are worth noting.

The DOP determines the number of processors that are used to execute a single query or index operation in parallel. The MDOP, on the other hand, specifies the maximum number of processors that can be used for parallel execution of a single query across the entire SQL Server instance. By default, the MDOP is set to 0, which means that SQL Server can use all available processors for parallel execution.

One important change in SQL Server 2022 is the introduction of "Intelligent DOP", which is a new DOP control mechanism that automatically adjusts DOP based on system performance and resource utilization. This feature can help optimize query performance in highly dynamic and variable workloads by more efficiently using system resources.

Another change in SQL Server 2022 is the introduction of a new default MDOP setting, which is based on the number of logical processors available in the system. This default setting is intended to simplify configuration and provide optimal performance for most workloads, but it can be overridden by manually setting the MDOP value.

In addition, SQL Server 2022 allows for more fine-grained control over DOP at the query level, with new options for setting DOP for individual operators within a query plan. This can help optimize complex queries with varying levels of parallelism requirements and improve overall query performance.

DOP and MDOP remain important features for optimizing query performance in SQL Server 2022, and the new enhancements and changes can help make these features more effective and efficient. As always, it's important to carefully consider the impact of these features on system resources and tune the settings appropriately for each workload to achieve optimal query performance.

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