How to Identify MAXDOP Value for Running/Completed Queries

 To find the MAXDOP (Maximum Degree of Parallelism) used by running queries in SQL Server, you can use Dynamic Management Views (DMVs) such as sys.dm_exec_requests and sys.dm_exec_query_profiles. These views provide details about query execution, including parallelism levels.
1. Checking MAXDOP for Running Queries
SELECT  
    r.session_id,  
    r.request_id,  
    r.start_time,  
    r.status,  
    r.cpu_time,  
    r.total_elapsed_time,  
    r.logical_reads,  
    r.writes,  
    r.dop AS MAXDOP,  -- Degree of Parallelism
    st.text AS sql_text  
FROM sys.dm_exec_requests r  
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) st  
WHERE r.dop > 1  -- Filtering only parallel queries
ORDER BY r.start_time DESC;

Explanation:
    r.dop: Shows the degree of parallelism (i.e., the number of CPU cores used for execution).
    r.session_id: Identifies the session running the query.
    r.status: Shows the execution status (e.g., running, suspended).
    st.text: Displays the actual SQL query text.
    Note: If dop = 1, the query is running serially without parallelism.
2. Checking MAXDOP for Completed Queries
SELECT  
    qs.execution_count,  
    qs.total_worker_time / qs.execution_count AS avg_worker_time,  
    qs.max_dop,  -- MAXDOP used
    st.text AS sql_text  
FROM sys.dm_exec_query_stats qs  
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) st  
ORDER BY qs.total_worker_time DESC;

3. Checking MAXDOP for Running Query Execution Plans
SELECT  
    er.session_id,  
    qp.query_plan  
FROM sys.dm_exec_requests er  
CROSS APPLY sys.dm_exec_query_plan(er.plan_handle) qp  
WHERE er.dop > 1;

Look for Parallelism (Gather Streams) in the query plan XML to confirm parallel execution.

4. Checking MAXDOP Setting at Database Level
EXEC sp_configure 'show advanced options', 1;  
RECONFIGURE;  
EXEC sp_configure 'max degree of parallelism';

To check the database-level MAXDOP setting in Azure SQL Database:
SELECT *  
FROM sys.database_scoped_configurations  
WHERE name = 'MAXDOP';

5. Checking MAXDOP for Index Operations
SELECT  
    r.session_id,  
    r.command,  
    r.dop,  
    st.text  
FROM sys.dm_exec_requests r  
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) st  
WHERE r.command LIKE '%INDEX%';