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CSS SQL Server Engineers

This is the official team Web Log for Microsoft Customer Service and Support (CSS) SQL Support. Posts are provided by the CSS SQL Escalation Services
  • Blog Post: Capping CPU using Resource Governor – The Concurrency Mathematics

    Here is what you need to know: A = πr 2 Okay, not really as that is the formula for the area of a circle but it does set the stage for this discussion.   I have been working with the CAP_CPU_PERCENT (RESOURCE POOL) setting as it relates to concurrency.   This turned into a mathematical...
  • Blog Post: As The World Turns: SQL Server NUMA Memory Node and the Operating System Proximity

    It felt a bit like ‘As The World Turns’ as I unraveled how the following worked so the title is a bit of a tribute to my grandmother.  She could not miss here ‘stories’ in the afternoon. Proximity Before I dive into the details I would like to talk about NUMA node proximity.    The...
  • Blog Post: Spatial Indexing: From 4 Days to 4 Hours

    Over the past month I have been involved in the optimization of a Spatial Index creation/rebuild.  Microsoft has several fixes included in the SQL Server 2012 SP1 CU7 Release I have been asked by several people to tell the story of how I was able to determine the problem code lines that allowed...
  • Blog Post: How It Works: SQL Server 2012 Database Engine Task Scheduling

    Over the years the SQL Server scheduling algorithms have been documented in various publications.  Specifically, ‘ The Guru’s Guide to SQL Server Architecture and Internals’ has a chapter, written by the scheduler developer (Sameer) and Ken; and I reviewed the technical content, covering the details...
  • Blog Post: Strange Sch-S / Sch-M Deadlock on Machines with 16 or More Schedulers

    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 Server SKU, SQL Server will enable lock partitioning...
  • Blog Post: SQL Server 2012 - True Black Box Recorder

    This would be a perfect time to post a blog talking about the new SQL Server 2012 features.  However, I am going to leave that activity to the marketing folks ( AlwaysOn, T-SQL Enhancements, … ).   I want to talk about something that might not appear on the top of a marketing or sales...
  • Blog Post: Assigning SQL Server, SQL Agent to a Processor Group (OOM, Hang, Performance Counters Always Zero for Buffer Pool, …)

    Suresh brought to my attention that we have been getting questions as to why SQL Server starts on group 1 and then group 2 and it is not predictable?  Then Tejas brought up another issues and since I worked on this way back before we released SQL 2008 R2 I went back to my notes to pull up some details...
  • Blog Post: SQL Server: Clarifying The NUMA Configuration Information

    The increased number of cores per socket is driving NUMA designs and in SQL Server support we are seeing more NUMA machines and less pure SMP machines.    For whatever reason over the past 2 weeks I have fielded a bunch of questions around NUMA and the information is good for everyone...
  • Blog Post: SQL Server 2008/2008 R2 on Newer Machines with More Than 8 CPUs Presented per NUMA Node May Need Trace Flag 8048

    Applies To:   SQL 2008, 2008 R2 and Denail builds The SQL Server developer can elect to partition memory allocations at different levels based on the what the memory is used for.   The developer may choose a global, CPU, Node, or even worker partitioning scheme.   Several of...
  • Blog Post: How It Works: Extended Event (sqlos.wait_info*)

    I was posed a good question today about how the wait_info* event works in SQL Server 2008. The easiest way for me to answer the question was to prove the behavior. using WAITFOR DELAY it shows the behavior nicely. From: Robert Dorr Sent: Wednesday, October 20, 2010 2:07 PM Subject: RE: Extended Events...
  • Blog Post: How It Works: Timer Outputs in SQL Server 2008 R2 - Invariant TSC

    I would love nothing more than to take you back to my high-school days running the 440 yard hurdles (yes yards not meters) where timing was done with a stop watch (you know the old, moving dial style) but timers on the PC don't allow that simplicity. I have discussed the timing behavior is SQL Server...
  • Blog Post: SQL Server 2008 R2 New Non-Yield Ring Buffer Information

    In 2002 the SQLOS team added specific checks for non-yielding scheduler issues. You may be familiar with the 178** series of errors like 17883 scheduler non-yield. Since 2002 the test matrix for SQL Server has flagged these errors and corrected them. With the evolution of SQL Server 2005, 2008 and now...
  • Blog Post: How It Works: Soft NUMA, I/O Completion Thread, Lazy Writer Workers and Memory Nodes

    There seems to be some semantic(s) confusion on the books online description of SOFT NUMA.    The area of confusion is from the SQL Server 2008 Books Online section, shown below. Soft-NUMA SQL Server allows you to group CPUs into nodes referred to as soft-NUMA. You usually configure soft...
  • Blog Post: High CPU with Reporting Services 2008

    I’ve run into two cases which fell down the same path and figured we should have some information out there regarding it.  The issue was that the customer’s instance of Reporting Services would just spike to 100% CPU usage.  During this time the end users did not notice any interruption in...
  • Blog Post: SQL Server reports working set trim warning message during early startup phase

    In the previous posts we have discussed the working set trim message “ A significant part of sql server process memory has been paged out ” that gets written to the SQL Server Error log. You can find the details about the various parameters that determine when this message is written to the error log...
  • Blog Post: SQLDumper unable to generate mdmp files in SQL Server 2008 Failover clusters

    SQLDumper utility is used by various components of the product to generate and save diagnostic information in the form of mini-dump and other log files. You will normally find the output files [with extension .mdmp, .txt and .log] created by sqldumper.exe in the LOG folder of the specific instance for...
  • Blog Post: SQL Server 2005 or 2008 Reporting Error 17883 - Stalled Scheduler Warnings

    SQL Server 2005 introduced a background worker to flush trace event streams.   The trace buffer is flushed when it becomes fully populated but a partially populated trace buffer remains in-memory until events fill the buffer or the background worker flushes the events to the stream.  Periodically...
  • Blog Post: SQLIOSim: Default Testing Pattern

    The SQLIOSim knowledge base article outlines the various configuration files in detail.  http://support.microsoft.com/kb/231619 - How to use the SQLIOSim utility to simulate SQL Server activity on a disk subsystem. I still get inquires about what should I run by default.   My answer is...
  • Blog Post: How It Works: SQL Server No Longer Uses RDTSC For Timings in SQL 2008 and SQL 2005 Service Pack 3 (SP3)

    Many of you have encountered the RDTSC timing variances that I outlined in an earlier blog post:   http://blogs.msdn.com/psssql/archive/2006/11/27/sql-server-2005-sp2-will-introduce-new-messages-to-the-error-log-related-to-timing-activities.aspx and http://blogs.msdn.com/psssql/archive/2007...
  • Blog Post: How It Works: What is behind the SQLCLR wait category in SQL Server 2008 Activity Monitor

    I was asked a question as the CSS First Aid Station at SQL PASS 2008 where the Activity Monitor kept showing the SQLCLR wait category as the top waiter, even when no other activity was going on.  After some digging I found that this is a bug and currently marked to be fixed SQL Server 2008 SP1. ...
  • Blog Post: Should I run SQLIOSim? - An e-mail follow-up from SQL PASS 2008

    From: Robert Dorr [mailto:rdorr@microsoft.com] Sent: Thursday, November 20, 2008 11:29 AM To: A SQL PASS MEMBER - CSS First Aid Station Question About SQLIOSim As we discussed at SQL PASS – SQLIOSim is an independent utility and has been used as part of the Windows Hardware Compatibility Testing...
  • Blog Post: How It Works: SQLIOSim - Running Average, Target Duration, Discarded Buffers ...

    The following is from a lengthy conversation I had with Kevin Kline.  I believe he will be posting more details along with his "Understanding SQLIOSim Output - http://sqlblog.com/blogs/kevin_kline/archive/2007/06/28/understanding-sqliosim-output.aspx )   ********** Final Summary for file...
  • Blog Post: How It Works: 17888 - All Schedulers on Node Appear Deadlocked

    Error 17888: All schedulers on Node ## appear deadlocked due to a large number of worker threads waiting on <<RESOURCE>>. Process Utilization ##%. SQL Server creates a Scheduler Monitor thread for each node.    One of the Scheduler Monitor tasks is to watch the schedulers assigned...
  • Blog Post: How It Works: Non-Yielding Resource Monitor

    I have addressed similar conditions error in a white paper: www.microsoft.com/technet/prodtechnol/sql/2005/diagandcorrecterrs.mspx 2008-01-20 19:01:26.11 Server      ***Stack Dump being sent to K:\MSSQL.3\MSSQL\LOG\SQLDump0001.txt 2008-01-20 19:01:26.11 Server     ...
  • Blog Post: How It Works: SQL Server 2005 I/O Affinity and NUMA Don't Always Mix

    Recently I have fielded several questions related to I/O affinity.  Allow me to outline the behavior and clear up misconceptions. When I/O affinity is enabled SQL Server creates a hidden scheduler for the Log Writer process as well as a special lazy writer thread for each of the bits set in the...
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