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  • Blog Post: Q and A: Ratio between AWE Allocated and VM Committed/Reserved in DBCC MEMORYSTATUS output

    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 manager only shows that SQL is using around 100MB...
  • Blog Post: Q & A: Does SQL Server always respond to memory pressure?

    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 memory and the server basically dies because there...
  • Blog Post: Talking points around SQL Server 2005 scalability

    Couple of weeks ago I did a talk on SQL Server 2005 scalability. The actual talk was not about the enormous amount of features that you can leverage in SQL Serve 2005 to make your application scale but rather how SQL 2005 achieves its scalability. In this post I present a set of talking points of the...
  • Blog Post: Q & A: I can't make SQL Server 2005 32 bit version to use all memory on the machine

    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. Is there a way to get around this and...
  • Blog Post: Set of new features in SQL Server 2005 enabled by SQLOS

    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 that some of you might be interested to take a...
  • Blog Post: Q and A: Enabling AWE settings for SQL Server 32 bit edition in WOW

    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, you should follow exactly the same procedure as...
  • Blog Post: Q and A: SQL Server memory allocated outside of Buffer Pool, formerly known as MemToLeave

    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 preferable memory manager for dynamic allocations...
  • Blog Post: Q and A: Do I need to run "sp_configure 'awe enabled', 1" to make 64 bit version of SQL Server use locked pages?

    The answer is No. The source of possible confusion came from one of my previous posts: http://blogs.msdn.com/slavao/archive/2005/11/15/493019.aspx . I apologize for the confusion. In order to make 64 bit version of SQL Server leverage locked pages all you need to do is to give lock pages in memory privilege...
  • Blog Post: Be Aware: 4GB of VAS under WOW, does it really worth it?

    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 to either 32 bit app you are using or dlls 32 bit...
  • Blog Post: Q and A: Clock Hands - what are they for?

    Q1 I read in your blog about the new algorithm with two clock hands to control memory consumption, but I really would like to understand exactly what the hands are doing and if they relate to the lazywriter. A1. In SQL Server 2005 we have separated database cache, Buffer Pool, and the rest of the...
  • Blog Post: Q and A: Virtual Address Space, VAS, reservation - why bother?

    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 don’t understand about ‘reserving memory’. When...
  • Blog Post: Q and A: x64 & AWE mechanism

    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 on x64 systems using x64 versions of the OS...
  • Blog Post: Final changes in SQL Server 2005's memory manager

    As you would expect in the last several months SQL 2005 went through rigorous testing. During the period we have identified and put several improvements that you might be interested to hear about. Memory Broker Analyzing SQL Server's behavior with respect to memory consumption from multiple...
  • Blog Post: Talking Points around Memory Manager in SQL Server 2005

    Yesterday I gave a talk around SQL Server 2005's memory manager. The talk was rather chalk talk. It included memory manager changes in SQL 2005 as well as changes post CTP15. For the talk I prepared several slides - basically talking points that I thought might be interesting to everyone. If you were...
  • Blog Post: Configuring SQL Server 2005 for Soft NUMA

    Sometimes I am surprised how issues come up the moment you mention them J . Recently, I have discussed Soft NUMA configurations in the article http://blogs.msdn.com/slavao/articles/441058.aspx . This week one of our customers had an interesting problem. The customer wanted to partition single SQL server...
  • Blog Post: SQL Server 2005 NUMA support & troubleshooting

    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 I would like to go over both Windows's and SQL Server...
  • Blog Post: SQLOS helps SQL Server to leverage hardware capabilities

    I just finished an article on how SQLOS helps SQL Server to leverage hardware capabilities http://blogs.msdn.com/slavao/articles/441058.aspx . It will be interesting to hear your comments, thoughts. Thanks a lot in advance
  • Blog Post: Q and A: Controlling size of a single cache in SQL 2005

    Q: I have teaching a class on Yukon for the Ascend program, and the class had a question I wanted to double check before answering. On an Itanium with 1 TB of RAM, the class’ curiosity asked, “If plan cache is very large “Then how does Plan Cache lookups work such that the plan lookup does not itself...
  • Blog Post: Be Aware: Using AWE, locked pages in memory, on 64 bit

    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 and actually could be useful on 64 bit platforms...
  • Blog Post: Be Aware: IA64 Stack Size

    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 of weeks I have been approached by our testers and...
  • Blog Post: SQLOS Caching

    Yukon caching vs SQL2000 What makes Yukon memory management different from SQL2000 is elaborative caching framework. In SQL2000 there are two major caches: data page cache, called Buffer Pool and procedure cache, cache of query plans. Buffer Pool and procedure cache are very tightly coupled. For example...
  • Blog Post: SQLOS's memory manager: responding to memory pressure

    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 why it is important. Memory pressure is categorized...
  • Blog Post: Changes in dbcc memorystatus in Yukon

    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 by SQLOS, SQL Server, memory manager Memory Manager...
  • Blog Post: SQLOS's memory manager and SQL Server's Buffer Pool

    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 ---------------- | Page Allocator | ---------------...
  • Blog Post: SQLOS - unleashed

    With SQL Server 2005 Beta 1 and Beta 2 you might have noticed that there is no ums.dll in the bin directory. The reason is simple it is no longer exists. In SQL2000 ums.dll provided SQL Server with user mode non-preemptive scheduling. So what happened in latest version? Have we removed non-preemptive...
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