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Blog Post: How It Works: sp_server_diagnostics – spinlock backoffs

SQL Server Support Content

There are numerous articles outlining how spinlocks work so I won’t cover the details in this post. Instead, I want to focus on the spinlockbackoffs value recorded in the sp_server_diagnostics output. Component = System <system spinlockBackoffs ...read more

on 12 Dec 2014
Blog Post: A faster CHECKDB – Part III

SQL Server Support Content

Bob Ward introduced Part 1 and Part 2 of ‘A faster CHECKDB’ as highlighted in the following links. Part 1: http://blogs.msdn.com/b/psssql/archive/2011/12/20/a-faster-checkdb-part-i.aspx Part 2: http://blogs.msdn.com/b/psssql/archive/2012/02/23 ...read more

on 10 Nov 2014
Blog Post: SQL Server MAX DOP Beyond 64 – Is That Possible?

SQL Server Support Content

I recently posted a blog outlining how the partitions of a table can be used in the calculation for the achievable max degree of parallelism (MAX DOP). http://blogs.msdn.com/b/psssql/archive/2014/09/04/a-partitioned-table-may-limit-the-runtime-max-dop ...read more

on 30 Oct 2014
Blog Post: A Partitioned Table May Limit the Runtime MAX DOP of Create/Alter Index

SQL Server Support Content

I was working with a 1.3 trillion row table in the Microsoft lab when I learned more about the ins and outs of this behavior. This issue is alluded to in SQL Server Books Online but allow me to expand on the behavior a bit more. ( http://msdn.microsoft ...read more

on 4 Sep 2014
Blog Post: How It Works: Behavior of a 1 Trillion Row Index Build (Gather Streams from SORT)

SQL Server Support Content

I ran into this behavior working on a 1 trillion row, spatial index build but the behavior can apply to any Gather Streams operator, retaining the sort order as rows pass though it. I was just surprised a bit by the behavior until I dug deeper ...read more

on 29 Apr 2014
Blog Post: How It Works: FileStream (RsFx) Garbage Collection–Part (2)

SQL Server Support Content

In a previous post I outlined the basics of File Stream, garbage collection: http://blogs.msdn.com/b/psssql/archive/2011/06/23/how-it-works-filestream-rsfx-garbage-collection.aspx This post continues the discussion, outlining specific details as to how ...read more

on 4 Apr 2014
Blog Post: AppDomain unloading messages flooding the SQL Server error log

SQL Server Support Content

This blog is built directly from a customer reported issue. As I helped investigate the source of the issue I thought it would be of interest to a broader audience – hopefully you find this interesting, as well. Allow me to provide some history ...read more

on 30 Jan 2013
Blog Post: DReplay Message: “Active connections exceed 8192, connection 8409 is waiting.”

SQL Server Support Content

This message was an interesting dive into the DReplay, session boundary logic that I thought I would share. Internally DReplay maintains a progressive, session queue. This queue is limited to 8192 entries and populated in connection replay ...read more

on 23 Jul 2013
Blog Post: How It Works: SQL Server (NUMA Local, Foreign and Away Memory Blocks)

SQL Server Support Content

The NODE an operating system page, physically belongs to can be acquired using the QueryVirtualMemoryEx Windows API. SQL Server uses this API to track locality of memory allocations. This blog is a very high level view of SQL Server behavior but ...read more

on 14 Dec 2012
Blog Post: How It Works: Gotcha: *VARCHAR(MAX) caused my queries to be slower

SQL Server Support Content

The scenario: Table has a NTEXT column that the customer wanted converted to NVARCHAR(MAX) Data has both small and large storage for different rows Issued ALTER TABLE … ADD COLUMN …NVarCharColumn… NVARCHAR(MAX) Issued update MyTable set NVarCharColumn ...read more

on 3 Dec 2012
Blog Post: T-SQL Update Takes Much Longer Than The Matching Select Statement

SQL Server Support Content

I realize the title is generic and that is because the problem is generic. On the surface it would not surprise me that an update takes longer than a select. (A little bit anyway.) There is logging, updates to index rows, triggers, replication ...read more

on 21 Sep 2012
Blog Post: Strange Sch-S / Sch-M Deadlock on Machines with 16 or More Schedulers

SQL Server Support Content

Since it took me several days to track down this bug, and I did learn a couple of new things along the way, I thought I would share some of my work. 16 or More CPUS When a system presents SQL Server with 16 or more CPUs, and you are using a high end SQL ...read more

on 31 Aug 2012
Blog Post: Under rare conditions, using IN clause can cause unexpected SQL behavior

SQL Server Support Content

I want to make you aware of a latest SQL Server 2008 hotfix documented in http://support.microsoft.com/kb/2791745 . Using large number of constants in IN clause can result in SQL Server termination unexpectedly. When this happens ...read more

on 12 Feb 2013
Blog Post: SQL Server–Storage Spaces/VHDx and 4K Sector Size

SQL Server Support Content

This blog outlines a new twist to my previous blog outlining issues with 4K sector sizes. SQL Server - New Drives Use 4K Sector Size: http://blogs.msdn.com/b/psssql/archive/2011/01/13/sql-server-new-drives-use-4k-sector-size.aspx In the previous post ...read more

on 15 May 2013
Blog Post: SQLIOSim Checksum Validations

SQL Server Support Content

I had a very specific question asked of me related to the SQLIOSIM.exe, checksum validation logic. It is pretty simple logic (on purpose) but effective so here are the basics. The key is that there are multiple memory locations used to hold the ...read more

on 5 Apr 2013
Blog Post: How Can Reference Counting Be A Leading Memory Scribbler Cause?

SQL Server Support Content

The concept of the memory scribbler comes up quite a bit in support. The term can often be over used but I ran into a specific example that commonly fools people, including support engineers. The random nature and even the resulting ...read more

on 12 Nov 2012
Blog Post: High CPU Troubleshooting with DMV Queries

SQL Server Support Content

High CPU Troubleshooting with DMV Queries Scenario: Recently, a customer called Microsoft Support with a critical performance issue that I worked on. Their SQL Server instance had 100% CPU utilization for a period, but the problem stopped without ...read more

on 17 Jun 2013
Blog Post: Optimizing partition split when the partition is not empty

SQL Server Support Content

Some of our Field Engineers, Kal Yella and Denzil Ribeiro ( @DenzilRibeiro ) have posted a blog that discusses how to optimize adding a partition when either the right most, or left most partition is not empty.. It is well worth the read, so we ...read more

on 13 Aug 2013
Blog Post: How It Works: Online Index Rebuild - Can Cause Increased Fragmentation

SQL Server Support Content

SQL Server Books Online alludes to the fragmentation possibility but does not fully explain that the Online Index rebuilding may increase fragmentation when it is allowed to run with MAX DOP > 1 and ALLOW_PAGE_LOCKS = OFF directives . The process of ...read more

on 5 Sep 2012
Blog Post: How It Works: SQL Server 32 bit PAE/AWE on (SQL 2005, 2008, and 2008 R2) – Not Using As Much RAM As Expected!

SQL Server Support Content

This issue was puzzling until we stepped through the code and studied it in some detail. The report was “SQL Server won’t use the physical memory I expect it to use.” Scenario: SQL Server 2008 R2, 32GB RAM - SQL only using ~22GB ...read more

on 11 Dec 2012
Blog Post: How It Works: CMemThread and Debugging Them

SQL Server Support Content

The wait type of CMemThread shows up in outputs such as sys.dm_exec_requests. This post is intended to explain what a CMemThread is and what you might be able to do to avoid the waits. The easiest way to describe a CMemThread is to talk about ...read more

on 20 Dec 2012

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Browse by Tags

Blog Post: How It Works: sp_server_diagnostics – spinlock backoffs

Blog Post: A faster CHECKDB – Part III

Blog Post: SQL Server MAX DOP Beyond 64 – Is That Possible?

Blog Post: A Partitioned Table May Limit the Runtime MAX DOP of Create/Alter Index

Blog Post: How It Works: Behavior of a 1 Trillion Row Index Build (Gather Streams from SORT)

Blog Post: How It Works: FileStream (RsFx) Garbage Collection–Part (2)

Blog Post: AppDomain unloading messages flooding the SQL Server error log

Blog Post: DReplay Message: “Active connections exceed 8192, connection 8409 is waiting.”

Blog Post: How It Works: SQL Server (NUMA Local, Foreign and Away Memory Blocks)

Blog Post: How It Works: Gotcha: *VARCHAR(MAX) caused my queries to be slower

Blog Post: T-SQL Update Takes Much Longer Than The Matching Select Statement

Blog Post: Strange Sch-S / Sch-M Deadlock on Machines with 16 or More Schedulers

Blog Post: Under rare conditions, using IN clause can cause unexpected SQL behavior

Blog Post: SQL Server–Storage Spaces/VHDx and 4K Sector Size

Blog Post: SQLIOSim Checksum Validations

Blog Post: How Can Reference Counting Be A Leading Memory Scribbler Cause?

Blog Post: High CPU Troubleshooting with DMV Queries

Blog Post: Optimizing partition split when the partition is not empty

Blog Post: How It Works: Online Index Rebuild - Can Cause Increased Fragmentation

Blog Post: How It Works: SQL Server 32 bit PAE/AWE on (SQL 2005, 2008, and 2008 R2) – Not Using As Much RAM As Expected!

Blog Post: How It Works: CMemThread and Debugging Them