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 I discussed that it was unsafe for the I/O subsystem...

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 data and do the comparison.   1.     ...

Parameter sniffing is a well known among SQL User community.   But I have seen variations of this frequently that need a bit creative handling and solution may not that straight forward. One of the variation is that a user changes the value of the parameter inside the procedure.  When...

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 a standard Heap, HeapCreate and the options (with...

We ran into an issue today that is a bug you may need to be aware of because of its behavior.   When a SQLCLR procedure calls back into the SQL Server (in proc provider) and executes sp_OA*, during the callback activity, it triggers a bug (currently filed and being evaluated) that results in...

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 of total memory and won’t use anymore. Let me try...

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 behaviors are so broad that these issues often take...

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...

I have been asked how to automate SQLIOSim on several occasions.  SQLIOSim is a utility to test SQL Server I/O integrity ( not performance ) patterns against a system without needing to install SQL Server on the system.  It ships with SQL Server 2008 and SQL Server 2008 R2 and is located in...

The is more of an FYI blog post but I have read several blog and forum posts on this subject and I decided to dig into the behavior which revealed a trace bug. For the vast majority of events the Session Login Name represents the originating session credentials where as the Login Name represents the...

In a previous blog I outlined how file stream transactions work and retain the before and after images of the file to allow various forms of recovery.  Reading that blog should be considered a prerequisite: http://blogs.msdn.com/b/psssql/archive/2008/01/15/how-it-works-file-stream-the-before-and...

This post is directly from an issue I have been working on.  The behavior is very difficult to simulate because of the flags and timings involved.   In this post I will attempt to describe the scenario and provide you with a simple workaround for your applications. Reproduction Steps 1...

A .NET Security Update (MS11-028) may end up causing issues with applications that make use of the .NET Framework, mostly resulting in applications being unable to launch, or loss of functionality within Native Applications that make use of .NET. In some cases, it could lead to an application crash....

My colleges asked me if 'squirrely' is a technical term and for this post the answer is yes.  CSS is not going to deny support to customers but SQL Server was not tested in this scenario so you may have chased yourself up a tree, hence I use the term squirrely. SQL Server 2005 introduced snapshot...

In a lengthy discussion this past week I was reminded that Jan 2011 is when the hard drive manufactures agreed to focus on drives with sector sizes of 4K. I have read all the latest materials about this over the past week and you can too. Just search for 512e or Advanced Format Sector sizes and you will...

I have had several questions on my blog post: http://blogs.msdn.com/b/psssql/archive/2010/08/03/how-it-works-error-18056-the-client-was-unable-to-reuse-a-session-with-spid-which-had-been-reset-for-connection-pooling.aspx related to SQL Server 2008's honoring of an query cancel (attention) during the...

When attempting to run dbcc checkdb or create a snapshot database you may encounter the following errors when using a UNC location that does not support all sparse file operations. 2010-09-21 17:27:26.47 spid82 Error: 17053, Severity: 16, State: 1. 2010-09-21 17:27:26.47 spid82 SidePageTable::Init()...

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...

I ran into an issue which has some aspects I found interesting and thought you might as well. When you do a select against the sys.messages virtual table the data is retrieved from the resource files (.RLL) files stored under <<Instance>>\Binn\Resource directory. This is done by loading the...

I encountered another interesting research issue to share with you. The documentation states RecordsAffected are for INSERT, UPDATE and DELETE but it might fool you. ------------------------------------------------------------------------------------ Sent: Monday, June 07, 2010 9:06 PM Subject: "set...

The short answer is that it is not an error and the message should be a WARNING. I looked at the latest, internal code base it has already been changed to a WARNING. if (!DeviceIoControl (volume, IOCTL_DISK_GET_CACHE_INFORMATION, NULL, 0, &m_diskCacheInfo, sizeof (m_diskCacheInfo), &dwBytes,...

I ran into an issue today that is documented but you have to know where to find it so I wanted to point it out. In the middle of a lengthy KB article # 907877 ( http://support.microsoft.com/kb/907877 ) the the following comment. "In a NUMA-enabled system, this value can be incorrect or negative...

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...

I put a presentation together quite some time ago going over various SQL Server I/O behaviors and relating them to the SQL Server I/O whitepapers I authored. I keep getting requests to post the presentation and the information is relevant from SQL 7.0 to SQL Server 2008 and beyond. Here are the RAW...

Previously I have posted details on backup/restore designs and how to tell what backup/restore is doing. http://blogs.msdn.com/psssql/archive/2009/03/03/how-it-works-sql-server-vdi-vss-backup-resources.aspx http://blogs.msdn.com/psssql/archive/2008/01/28/how-it-works-sql-server-backup-buffer-exchange...