How to create a Deadlocked Scheduler Scenario at will

  First, please do not try this on your production server, because it will actually work. Second, this example is to illustrate how Deadlock scheduler issues can and do occur with the goal of increasing your understanding of the problem. Over the years of working with SQL Server, I learned that to understand a technology…

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Meditation: The Tao of the Deadlock Scheduler in SQL Server

Just thought I would summarize the concept of a SOS Scheduler and a Deadlocked Scheduler since many have inquired over the years for a brief summary of these concepts   UMS/SOS Scheduler in SQL  Server Since SQL Server 7.0, SQL  Server has used its own scheduling mechanism, called UMS (User-mode scheduler)  in 7.0 and 2000 and…

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Tasks, Workers, Threads, Scheduler, Sessions, Connections, Requests – what does it all mean?

With this meditation I attempt to explain what some of the more common concepts that get used with SQL Server thread management and scheduling are. Parable: There was an all-powerful, but humble and benign Master, whom the workers revered and humbly served. The master accepted requests from other kingdoms and graciously agreed to grant all…

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Meditation: Is IOCP listener actually listening?

What is the IOCP Listener? The IOCP listener is a dedicated system thread that accepts incoming connections to SQL Server. It is a SQL Network Interface (SNI)-layer thread that listens for TCP/IP sockets or Named Pipes traffic (VIA is going away but still in the code). When a connection comes in, the listener accepts it…

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