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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: 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
Blog Post: All about RollbackSnapshotTempDB...

SQL Server Support Content

I’ve been recently involved in several cases where Databases named RollbackSnapshotTempDB +<someGUID> were generating confusion. The purpose of this post is to clarify their origin and use and to enable SQL Server admins to know what to do ...read more

on 7 Nov 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: SQL Server: Correlating Timestamps From Various Data Points

SQL Server Support Content

I was looking at data from a customer, in a different time zone (UTC+1) from mine, this week involving SQL Server AlwaysOn (HADRON) and found that lining up the timestamps in the various logs was challenging. Some times are local to the SQL ...read more

on 11 Sep 2012
Blog Post: Every time I ‘ATTACH DATABASE’ SQL logs error 1314 for SetFileIoOverlappedRange

SQL Server Support Content

Turns out this is an issue in the SQL Server code and the error is a bit noisy during attach database. When opening the database files, SQL Server calls SetFileIoOverlappedRange (when enabled properly) in order to help improve I/O performance. This ...read more

on 16 Oct 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: 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: 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: How It Works: Maximizing Max Degree Of Parallelism (MAXDOP)

SQL Server Support Content

I was working on an index build issue for an 80 CPU system and kept seeing that only 64 CPUs were getting used. I had carefully studied sys . dm_os_spinlock_stats and sys . dm_os_wait_stats along with performance counters, memory usage pattern, and I ...read more

on 27 Sep 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: When Does sp_prepare Return Metadata

SQL Server Support Content

I was running an RML Utilities Suite test pass and encountered varying behavior from our sp_prepare suite. Here is what I uncovered. The command sp_prepare returns (or does not return) metadata depending on the server version. For the client ...read more

on 23 Jul 2013
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: 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: How It Works: The I/O Path: SQL Server Running in Windows Azure Virtual Machine (IaaS)

SQL Server Support Content

Note: This blog is based on behavior as of June 2013. At Microsoft we continue to evolve and enhance our products so the behavior may change over time. The I/O path for SQL Server, running on Windows Azure Virtual Machines, uses Windows Azure storage ...read more

on 3 Jun 2013

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Browse by Tags

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: CMemThread and Debugging Them

Blog Post: All about RollbackSnapshotTempDB...

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

Blog Post: SQL Server: Correlating Timestamps From Various Data Points

Blog Post: Every time I ‘ATTACH DATABASE’ SQL logs error 1314 for SetFileIoOverlappedRange

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: SQLIOSim Checksum Validations

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: How It Works: Maximizing Max Degree Of Parallelism (MAXDOP)

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

Blog Post: When Does sp_prepare Return Metadata

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

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: How It Works: The I/O Path: SQL Server Running in Windows Azure Virtual Machine (IaaS)