Questions tagged [maxdop]
Max Degree of Parallelism (MAXDOP) is a configuration option that determines the maximum number of threads dispatched by SQL Server to service queries that might benefit from parallel operation.
53 questions
2 votes
1 answer
372 views
How should MAXDOP be configured on stacked instances?
There is good general advice for how to configure Maximum Degree of Parallelism (MAXDOP). However, I am in a special circumstance. There are two instances on my box. If I have 16 cores, how should I ...
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16 votes
2 answers
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Why is SQL Server setup recommending MAXDOP 8 here?
I'm running SQL Server 2022 RC1 setup on an AWS i3.16xlarge with 2 sockets, 2 NUMA nodes, 32 logical processors per node, 64 logical processors altogether. Setup is recommending MAXDOP 8: But if you ...
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0 votes
1 answer
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can use maxdop on online modifying column in mssql 2019?
I want to change data type of a column of my table in SQL Server 2019. My table has 50,000,000 row and it's very important. I want to do this operation online and also handle maxdop to avoid CPU over ...
-1 votes
2 answers
576 views
How to estimate cpu based on peak rate of query requests?
By default, SQL Server allows a maximum of 32767 concurrent connections which is the maximum number of users that can simultaneously log in to the SQL server instance. I am developing 10 web apis ...
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-1 votes
2 answers
783 views
Why does MAXDOP = 0 result in high CXPACKET wait time?
During a parallel query execution (whether or not to go parallel is decided by the cost threshold for parallelism) MAXDOP limits the number of tasks per request. Assuming cost threshold for ...
- 3,602
1 vote
1 answer
2k views
What is the num of NUMA nodes for MAXDOP calculation when there is discrepancy between various ways to count the NUMA nodes?
Querying the dm_os_performance_counters shows that I have 2 NUMA nodes: select * from sys.dm_os_performance_counters where object_name = 'SQLServer:Buffer Node' and counter_name = 'Page life ...
- 3,602
-1 votes
1 answer
132 views
Why is max dop recommended value related to the number of NUMA nodes?
Sql server recommendation is to decide max dop based on number of processors in a single Numa node. Given a system with 4 Numa nodes, each having 6 processors, the max dop recommended hence would be 6....
- 3,602
0 votes
2 answers
518 views
Is socket a synonym of NUMA, and virtual processor synonym of physical processor in a virtualized SQL server environment?
Link: https://learn.microsoft.com/en-US/sql/database-engine/configure-windows/configure-the-max-degree-of-parallelism-server-configuration-option?view=sql-server-ver15#Recommendations I understand the ...
- 3,602
1 vote
3 answers
2k views
Can setting max dop = number of cpu's cause situation where a single query blocks other queries?
I have sql server with 8 cpus. Max worker threads setting is say 850. Max dop is say 8. And cost thread hold for parallelism is 50. This means sql server will breakdown a query going above cost ...
- 3,602
0 votes
1 answer
180 views
Query plan XML: one stmt's DegreeOfParallelism is 1 for any maxdop other than 1 (maxdop 1 leads to DegreeOfParallelism = 0 with reason MaxDopSetToOne)
I have a procedure with two SELECTs. One statement respects the server's/database's/query hint's maxdop setting and uses parallelism, the other is being difficult and never going parallel. The 8 core ...
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6 votes
1 answer
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What happens to queries that are in progress when we change maxdop in live system and while they are executing?
We have a prod system that sometimes gets stuck and nothing we do helps but changing maxdop parameter on live system, after we change that all gets back normal. And it does not even matter if we ...
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-3 votes
1 answer
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Striping disks with MAXDOP 1
We're working with a vendor who is insisting we use MAXDOP = 1 (I know...). They are also emphasizing the importance of striping our data files across different disks. As I understand it, an I/O ...
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0 votes
1 answer
233 views
Should I change parallelism (MaxDop and Threshold)?
Seems like I have problems with parallelism because largest wait types are CXCONSUMER and CXPACKET. Server has 8 cores. So I am planning to bump up Cost Threshold to 50 and MaxDop to 4 Currently I ...
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0 votes
1 answer
374 views
How to reduce the maximum degree of parallelism at session level?
I have inherited a legacy application that includes a job that creates performance issue at instance level. The DBA told us about this and our team needs to fix the stored procedure that is the most ...
- 1,193
0 votes
1 answer
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Will an underpowered mirror host cause: The query processor could not start the necessary thread resources for parallel query execution [duplicate]
We recently moved our 2016 sql server mirror into Azure, but it's on an underpowered machine. Our main database server has 16 physical cores with hyper threading and 2 numa nodes. We have set the ...
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