Slava Oks's WebLog

Our customers observed very interesting behavior on high end Hyperthreading (HT) enabled hardware. They noticed that in some cases when high load is applied SQL Server CPU usage increases significantly but SQL Server performance degrades. Occasionally...

Q: I thought I've seen reference recently to problems with SQL2005 not releasing memory when under pressure, and this was possibly due to the Lock Pages In Memory option. We have a server where this seems to be happening, i.e. SQL2005 uses all available...

We have already talked about Windows AWE mechanism on 32 bit and how SQL Server utilizes it. Today I would like to go over AWE & related mechanism on 64 bit platforms. To some people it comes as a surprise that AWE mechanism is still present...

SQLOS's memory manager consists of several components such as memory nodes, memory clerks, memory caches, and memory objects. Fig 1. depicts memory manager components and their relationship: ---------------- | Memory Object | ---------------- | | V -...

As I promised last time here comes next post on memory J . Remember, my eventual goal is to reveal how memory management works in SQL Server but for you to really appreciate it, I think, you do need to get good feeling on how Windows manages memory. Understanding...

This is my first post in this category so I am really looking forward to your comments :-) Today I would like to cover a specific feature related to our implementation of C++ exception handling. Every day I realize that not many people are familiar with...

Q: Hello Slava, I would like to confirm my understanding that on SQL 2005 64 bit edition it is recommended to grant Lock Pages in Memory right to the SQL account and then turn on the AWE setting. Thanks A: Yes, we do recommend to turn on Lock pages...

Resource Monitor and Memory Pressure When configuring SQL Server it is very important to understand how it reacts to memory pressure. I have already spent significant amount of time describing types of memory pressure. In this post you will understand...

SQL Server 2005 has been designed to take advantage of NUMA features exposed by both hardware and the Windows operating system. There are several caveats that you need to be aware when attempting to run SQL Server on NUMA platforms. In this post...

Today, I received following question Q: Slava, I have a question for you. Sql 2000 is documented to support a maximum of 64GB when used with 2000 datacenter edition. I assume this is the limit of 2000 Datacenter, but is it also a limit defined in sql...

Today I received following question: Hello, We will be running Windows Server 2003 x64 with SQL Server 2005 x64. I would think AWE would not come into the picture in this scenario. I'm trying to find out more about SQL Server 2005 memory management...

So far I touched on subjects that have been widely discussed in the industry. Today I would like to talk about a subject that you would hardly find information about: memory pressure.. On a surface the subject appears simple but in reality this is not...

Memory is a set of common resources shared by applications, their components and operating system. One needs to be very specific when referring to a given memory resource. Mistakenly, in many cases, developers, users, DBAs refer to different memory resources...

You probably have used dbcc memory status command in SQL2000. In Yukon we have changed output of dbcc memorystatus to reflect new memory manager design, covered in my previous post. The first part of the output represents overall amount of memory consumed...

Q: What kind of ratio should you expect to see between AWE Allocated and VM Committed/Reserved? We are running 8GB with a cap of 7GB in the max server memory and yet the VM Committed is around 100MB. I was first shocked to see that the sqlservice in task...

SQL Server 2005 has a large number of DMVs that you can take advantage of especially when you try to understand behavioral characteristics of your SQL Server 2005 installation. DMVs expose enormous amount of information but how can you make use of it...

Couple of weeks ago I had a chance to visit set of our customers and talk to them directly. It was an unforgettable experience. As a part of the visit I made set of presentations related to SQLOS and new features it enables in SQL Server 2005. I thought...

By now you have heard a lot about the fact that under WOW a 32 bit process can get 4GB of VAS. I agree this is great, but I would like you to be aware of something that might hit you really hard. As it turns out enabling 4GB VAS can be problematic due...

sys.dm_os_waiting_tasks One can run lots of interesting queries using this view. You can even use this view to perform deadlock detection that is not resolvable by deadlock monitor, DM. For example if you have tasks waiting on external resources such...

sys.dm_os_schedulers Q. Do I need to by more CPUs? In order to answer this question you have to find out if your load is really CPU bounded. Your load is really CPU bounded if a number of runnable tasks per each scheduler always greater than...

Q. Under SQL Server 2000 Is the memtoleave concept still valid under 64-bit? A. Yes. If SQL Server’s component requests memory larger than 8 KB block, the block will be allocated outside of Buffer Pool. Remember, inside of SQL Server, Buffer Pool is...

Q. A customer wants to run SQL 2000 SP4 in a Windows Server 2003 SP1 x64 edition. They did the installation without problems but SQL Server is not using more than 4GB of memory. Is it possible to enable AWE in this configuration? A. The answer is yes...

Stack subject in Windows OS is fascinating. There are so many interesting technical problems surrounding it. The moment you think you fully understand everything about stack you suddenly discover yet another mystery. And so it goes. In the last couple...

Seems like today is a question day :-). I will attempt to answer several questions about VAS I got today: Q1. There is one aspect of Virtual Memory that is just not clear yet. I think I understand about VAS, but maybe not as much as I could, but I...

I’m currently using the RTM+SP1 x86-SQL2005 build on a server which has 32GB of physical memory. I notice that during ramp-up the memory usage (as seen under task manager) increases to about 28GB (i.e. “Available memory” reduces to 4GB) and stays there...