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  • Using LINQ Lambda Expressions to Design Customizable Generic Components

    LINQ makes code easier to write and maintain by abstracting the data source. It provides a uniform way to handle widely diverse data structures within an application. LINQ’s Lambda syntax is clever enough even to allow you to create generic building blocks with hooks into which you can inject arbitrary functions. Michael Sorens explains, and demonstrates with examples.

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  • Hyper-V R2 Live Migration

    Reliability is one of the great payoffs to virtualization, and failover clustering has got a whole lot better with Windows Server 2008 and Hyper-V. Now, you get failover without any downtime for the virtual machine. Jaap tells you how to implement it.

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  • Exposing an MVC Application Through SharePoint

    - by Damon
    Below you will find my presentation slides and demo files for my SharePoint TechFest 2010 presentation on Exposing an MVC Application through SharePoint.  One of the points I forgot to mention goes back to the performance and licensing benefits of this approach.  If you have a SharePoint box that is completely slammed, you can put the MVC application on a separate web server and essentially offload the application processing to another server.  In terms of licensing, you can leave SharePoint off that new server and just access SharePoint data via web services from the box.  This makes it a lot cheaper if you have MOSS - but if you're just running WSS then it may not have as many cost benefits.  Remember, programming against the web services is not always the easiest thing, so you have to weight the cost/benefit ratio when making such a determination.

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  • Red Gate's on the road in 2012 - Will you catch us?

    - by RedAndTheCommunity
    Annabel Bradford, our Communities and Events Manager, tells all about her experience of our 1st SQL Saturday of the year. The first stop this year was SQL Saturday #104 Colorado Springs, back in early January. I made the trip across from the UK just for this SQL Saturday event, and I'm so glad I did. I picked up Max from Red Gate's Pasadena office and we flew into Colorado Springs airport late on Friday evening to be greeted by freezing temperatures, which was quite a shock after the California sunshine. Rising before the sun, we arrived at Mr Biggs, the venue for the event, in the darkness. It was great to see so many smiling attendees so bright and early on a Saturday morning. Everyone was eager to learn more about SQL Server, and hundreds of people came and chatted with us at the table, saw demos and learnt more about Red Gate tools. The event highlights for the attendees were definitely the unlimited lazer quest, bowling and pool available during the break times. For Max, Grant Fritchey and I on the Red Gate table, the highlights have to be meeting customers and getting the opportunity to meet attendees who'd heard of, but wanted to know more about, Red Gate. We were delighted to hear lots of valuable feedback that we took back to share with the team. As a thank you for sharing insights about their work lives and how they use SQL Server and Red Gate tools, attendees are able to take away Red Gate SQL Server books. We aim to have a range of titles available when we exhibit, so that attendees can choose a book that's going to be most interesting to them, and that they can use as a reference back at the office. Every time I meet a Red Gate user or a member of the SQL community, I'm always overwhelmed by the enthusiasm they have for their industry. Everyone who gives up their time to learn more about their job should be rewarded, and at Red Gate we like to do just that. Red Gate has long supported the SQL community through sponsorship to facilitate user group meetings and community events, but it's only though face-to-face contact that we really get a chance to see the impact of our support. I hope we'll have the chance to see you on the road at some point this year. We'll be at a range of events, including free SQL Saturdays, one day free events 'the Red Gate way', two-day Rallys, and full-week conferences. Next stop is SQL Saturday #109 Silicon Valley on March 3rd where you'll meet Jeff and Arneh, two of our US-based SQL team members. Be sure to ask them any questions you've got about the Red Gate tools, as these guys will be delighted to hear your questions, show you the options, and will make a note of your feedback to send through to the development team. Until the next time. Happy learning! Annabel                         Grant, Max and Annabel at SQL Saturday #104 Colorado Springs

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  • The Politics of Junk Filtering

    - by mikef
    If the national postal service, such as the Royal Mail in the UK, were to go through your letters and throw away all the stuff it considered to be junk instead of delivering it to you, you might be rather pleased until you discovered that it took a too liberal decision about what was junk. Catalogs you'd asked for? Junk! Requests from charities? Who needs them! Parcels from competing carriers? Toss them away! The possibility for abuse for an agency that was in a monopolistic position is just too scary to tolerate. After all, the postal service could charge 'consultancy fees' to any sender who wanted to guarantee that his stuff got delivered, or they could even farm this out to other companies. Because Microsoft Outlook is just about the only email client used by the international business community in the west, its' SPAM filter is the final arbiter as to what gets read. My Outlook 2007, set to the default settings, junks all the perfectly innocent email newsletters that I subscribe to. Whereas Google Mail, Yahoo, and LIVE are all pretty accurate in detecting spam, Outlook makes all sorts of silly mistakes. The documentation speaks techno-babble about 'advanced heuristics', but the result boils down to an inaccurate mess. The more that Microsoft fiddles with it, the stickier the mess. To make matters worse, it still lets through obvious spam. The filter is occasionally updated along with other automatic 'security' updates you opt for automatic updates. As an editor for a popular online publication that provides a newsletter service, this is an obvious source of frustration. We follow all the best-practices we know about. We ensure that it is a trivial task to opt out of receiving it. We format the newsletter to the requirements of the Service Providers. We follow up, and resolve, every complaint. As a result, it gets delivered. It is galling to discover that, after all that effort, Outlook then often judges the contents to be junk on a whim, so you don't get to see it. A few days ago, Microsoft published the PST file format specification, under pressure from a European Union interoperability investigation by ECIS (the European Committee for Interoperable Systems). The objective was that other applications could then access existing PST files so as to migrate from existing Outlook installations to other solutions. Joaquín Almunia, the current competition commissioner, should now turn his attention to the more subtle problems of Microsoft Outlook. The Junk problem seems to have come from clumsy implementation of client-side spam filtering rather than from deliberate exploitation of a monopoly on the desktop email client for businesses, but it is a growing problem nonetheless. Cheers, Michael Francis

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  • Why not to use StackTrace to find what method called you

    - by Alex.Davies
    Our obfuscator, SmartAssembly, does some pretty crazy reflection. It's an obfuscator, it's sort of its job to do things in the most awkward way possible. But sometimes, you can go too far. One such time is this little gem from the strings encoding feature: StackTrace stackTrace = new StackTrace(); StackFrame frame = stackTrace.GetFrame(1); Type ownerType = frame.GetMethod().DeclaringType; It's designed to find the type where the calling method is defined. A user found that strings encoding occasionally broke on x64 systems. Very strange. After some debugging (thank god for Reflector Pro, it would be impossible to debug processed assemblies without it) I found that the ownerType I got back was wrong. The reason is that the x64 JIT does tail call optimisation. This saves space on the stack, and speeds things up, by throwing away a method's stack frame if the last thing that it calls is the only thing returned. When this happens, the call to StackTrace faithfully tells you that the calling method is the one that called the one we really wanted. So using StackTrace isn't safe for anything other than debugging, and it will make your code fail in unpredictable ways. Don't use it!

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  • Time to Check Your Servers

    - by fatherjack
    Do you know how to find the time that your SQL Server started? Since SQL Server 2008 you can use: SELECT sqlserver_start_timeFROM sys.dm_os_sys_info On one of my servers this gives me: This is great, and can be used in lots of ways. I happened across the [sys].[dm_exec_requests]view the other day and out of curiosity ran the query SELECT MIN(start_time) AS [start time]FROM [sys].[dm_exec_requests] AS der And I was surprised to see the result as: Almost exactly an hour different. Now as...(read more)

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  • What do you call an obfuscator that isn't an obfuscator?

    - by Alex.Davies
    SmartAssembly, formerly {smartassembly}, version 5 is now available as an Early Access Build. You can get it here: http://www.red-gate.com/MessageBoard/viewforum.php?f=116 We're having second thoughts about the name change though. It isn't that we like the curly brackets, far from it. The trouble is that the first rule of product naming is to name a product by what it does. SmartAssembly may make an assembly smarter, but that's not something people really google for. The trouble is, I can't think of a better name for it. That's because SmartAssembly really does two completely separate things: Obfuscates Sets up your assembly for the awesome exception reports which get sent to you whenever your application crashes. You may have been (un?)lucky enough to see one in reflector if you use it. This is what those exception reports look like when they arrive back with the developer: Look at all those local variables! If you ask me, this is much cooler than the obfuscation. So obviously we don't want to call it just "Red Gate Obfuscator" or something, because it doesn't do justice to the exception reporting. What would you call it?

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  • The clock hands of the buffer cache

    - by Tony Davis
    Over a leisurely beer at our local pub, the Waggon and Horses, Phil Factor was holding forth on the esoteric, but strangely poetic, language of SQL Server internals, riddled as it is with 'sleeping threads', 'stolen pages', and 'memory sweeps'. Generally, I remain immune to any twinge of interest in the bowels of SQL Server, reasoning that there are certain things that I don't and shouldn't need to know about SQL Server in order to use it successfully. Suddenly, however, my attention was grabbed by his mention of the 'clock hands of the buffer cache'. Back at the office, I succumbed to a moment of weakness and opened up Google. He wasn't lying. SQL Server maintains various memory buffers, or caches. For example, the plan cache stores recently-used execution plans. The data cache in the buffer pool stores frequently-used pages, ensuring that they may be read from memory rather than via expensive physical disk reads. These memory stores are classic LRU (Least Recently Updated) buffers, meaning that, for example, the least frequently used pages in the data cache become candidates for eviction (after first writing the page to disk if it has changed since being read into the cache). SQL Server clearly needs some mechanism to track which pages are candidates for being cleared out of a given cache, when it is getting too large, and it is this mechanism that is somewhat more labyrinthine than I previously imagined. Each page that is loaded into the cache has a counter, a miniature "wristwatch", which records how recently it was last used. This wristwatch gets reset to "present time", each time a page gets updated and then as the page 'ages' it clicks down towards zero, at which point the page can be removed from the cache. But what is SQL Server is suffering memory pressure and urgently needs to free up more space than is represented by zero-counter pages (or plans etc.)? This is where our 'clock hands' come in. Each cache has associated with it a "memory clock". Like most conventional clocks, it has two hands; one "external" clock hand, and one "internal". Slava Oks is very particular in stressing that these names have "nothing to do with the equivalent types of memory pressure". He's right, but the names do, in that peculiar Microsoft tradition, seem designed to confuse. The hands do relate to memory pressure; the cache "eviction policy" is determined by both global and local memory pressures on SQL Server. The "external" clock hand responds to global memory pressure, in other words pressure on SQL Server to reduce the size of its memory caches as a whole. Global memory pressure – which just to confuse things further seems sometimes to be referred to as physical memory pressure – can be either external (from the OS) or internal (from the process itself, e.g. due to limited virtual address space). The internal clock hand responds to local memory pressure, in other words the need to reduce the size of a single, specific cache. So, for example, if a particular cache, such as the plan cache, reaches a defined "pressure limit" the internal clock hand will start to turn and a memory sweep will be performed on that cache in order to remove plans from the memory store. During each sweep of the hands, the usage counter on the cache entry is reduced in value, effectively moving its "last used" time to further in the past (in effect, setting back the wrist watch on the page a couple of hours) and increasing the likelihood that it can be aged out of the cache. There is even a special Dynamic Management View, sys.dm_os_memory_cache_clock_hands, which allows you to interrogate the passage of the clock hands. Frequently turning hands equates to excessive memory pressure, which will lead to performance problems. Two hours later, I emerged from this rather frightening journey into the heart of SQL Server memory management, fascinated but still unsure if I'd learned anything that I'd put to any practical use. However, I certainly began to agree that there is something almost Tolkeinian in the language of the deep recesses of SQL Server. Cheers, Tony.

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  • Using SQL Sentry Plan Explorer

    - by fatherjack
    LiveJournal Tags: How To,SSMS,Tips and tricks,Execution Plans This is a quick tip that I hope will help you use SQL Sentry's Plan Explorer tool. It's a really great tool for viewing Execution Plans - something that SSMS isn't too great at. If you don't have the tool then you can download it for free from http://www.sqlsentry.net/plan-explorer/sql-server-query-view.asp. So, just a little setup is required before I can show you the tip in full. Create a directory on your Desktop called Execution...(read more)

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  • Back-sliding into Unmanaged Code

    - by Laila
    It is difficult to write about Microsoft's ambivalence to .NET without mentioning clichés about dog food.  In case you've been away a long time, you'll remember that Microsoft surprised everyone with the speed and energy with which it introduced and evangelised the .NET Framework for managed code. There was good reason for this. Once it became obvious to all that it had sleepwalked into third place as a provider of development languages, behind Borland and Sun, it reacted quickly to attract the best talent in the industry to produce a windows version of the Java runtime, with Bounds-checking, Automatic Garbage collection, structures exception handling and common data types. To develop applications for this managed runtime, it produced several excellent languages, and more are being provided. The only thing Microsoft ever got wrong was to give it a stupid name. The logical step for Microsoft would be to base the entire operating system on the .NET framework, and to re-engineer its own applications. In 2002, Bill Gates, then Microsoft Chairman and Chief Software Architect said about their plans for .NET, "This is a long-term approach. These things don't happen overnight." Now, eight years later, we're still waiting for signs of the 'long-term approach'. Microsoft's vision of an entirely managed operating system has subsided since the Vista fiasco, but stays alive yet dormant as Midori, still being developed by Microsoft Research. This is an Internet-centric fork of the singularity operating system, a research project started in 2003 to build a highly-dependable operating system in which the kernel, device drivers, and applications are all written in managed code. Midori is predicated on the prevalence of connected systems, with provisions for distributed concurrency where application components exist 'in the cloud', and supports a programming model that can tolerate cancellation, intermittent connectivity and latency. It features an entirely new security model that sandboxes applications for increased security. So have Microsoft converted its existing applications to the .NET framework? It seems not. What Windows applications can run on Mono? Very few, it seems. We all thought that .NET spelt the end of DLL Hell and the need for COM interop, but it looks as if Bill Gates' idea of 'not overnight' might stretch to a decade or more. The Operating System has shown only minimal signs of migrating to .NET. Even where the use of .NET has come to dominate, when used for server applications with IIS, IIS itself is still entirely developed in unmanaged code. This is an irritation to Microsoft's greatest supporters who committed themselves fully to the NET framework, only to find parts of the Ambivalent Microsoft Empire quietly backsliding into unmanaged code and the awful C++. It is a strategic mistake that the invigorated Apple didn't make with the Mac OS X Architecture. Cheers, Laila

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  • Why lock statements don't scale

    - by Alex.Davies
    We are going to have to stop using lock statements one day. Just like we had to stop using goto statements. The problem is similar, they're pretty easy to follow in small programs, but code with locks isn't composable. That means that small pieces of program that work in isolation can't necessarily be put together and work together. Of course actors scale fine :) Why lock statements don't scale as software gets bigger Deadlocks. You have a program with lots of threads picking up lots of locks. You already know that if two of your threads both try to pick up a lock that the other already has, they will deadlock. Your program will come to a grinding halt, and there will be fire and brimstone. "Easy!" you say, "Just make sure all the threads pick up the locks in the same order." Yes, that works. But you've broken composability. Now, to add a new lock to your code, you have to consider all the other locks already in your code and check that they are taken in the right order. Algorithm buffs will have noticed this approach means it takes quadratic time to write a program. That's bad. Why lock statements don't scale as hardware gets bigger Memory bus contention There's another headache, one that most programmers don't usually need to think about, but is going to bite us in a big way in a few years. Locking needs exclusive use of the entire system's memory bus while taking out the lock. That's not too bad for a single or dual-core system, but already for quad-core systems it's a pretty large overhead. Have a look at this blog about the .NET 4 ThreadPool for some numbers and a weird analogy (see the author's comment). Not too bad yet, but I'm scared my 1000 core machine of the future is going to go slower than my machine today! I don't know the answer to this problem yet. Maybe some kind of per-core work queue system with hierarchical work stealing. Definitely hardware support. But what I do know is that using locks specifically prevents any solution to this. We should be abstracting our code away from the details of locks as soon as possible, so we can swap in whatever solution arrives when it does. NAct uses locks at the moment. But my advice is that you code using actors (which do scale well as software gets bigger). And when there's a better way of implementing actors that'll scale well as hardware gets bigger, only NAct needs to work out how to use it, and your program will go fast on it's own.

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  • What Counts For a DBA: Ego

    - by Louis Davidson
    Leaving aside, for a second, Freud’s psychoanalytical definitions, the term “ego” generally refers to a person’s sense of self, and their self-esteem. In casual usage, however, it usually appears in the adjectival form, “egotistical” (most often followed by “jerk”). You don’t need to be a jerk to be a DBA; humility is important. However, ego is important too. A good DBA needs a certain degree of self-esteem…a belief and pride in what he or she can do better than anyone else can. The ideal DBA needs to be humble enough to admit when they are wrong but egotistical enough to know when they are right, and to stand up for that knowledge and make their voice heard. In most organizations, the DBA team is seriously outnumbered by headstrong developers and clock driven managers, and “great” DBAs will often be outnumbered by…well…the not so great. In order to be heard in this environment, a DBA will not only need to be very skilled, but will also need a healthy dose of ego. As Freud might have put it, the unconscious desire of the DBA (the id) is for iron-fist control over their databases, and code that runs in them. However, the ego moderates this desire, seeking to “satisfy the id in realistic ways that, in the long term, bring benefit rather than grief“. In other words, the ego understands the need to exert a measure of control and self-belief, but also to tolerate and play nicely with developers and other DBAs. The trick, naturally, is learning how to be heard when it is important, but also to make everyone around you welcome that input, even when you have to be bold to make the “I know what I am talking about, and you…well…not so much” decisions. Consider a baseball team, bottom of the ninth inning of the championship game, man on first and down one run. Almost anyone on that team will have the ability to hit a home run, but only one or two will have the iron belief that they can pull it off in this critical, end-game situation. The player you need in this situation is the one who has passionately gone the extra mile preparing for just this moment, is bursting at the seams with self-confidence, and can look the coach in the eye and state, boldly, “Put me in, I am your best bet“. Likewise, on those occasions when high customer demand coincides with copious system errors, and panic is bubbling just beneath the surface, you don’t need the minimally qualified support person, armed with the “reboot and hope” technique (though that sometimes works!). You need the DBA who steps up and says, “Put me in” and has the skill and tenacity to back up those words and to fix the pinpoint and fix the problem, whatever it takes, while keeping customers and managers happy. Of course, the egotistical DBA will happily spend hours telling you how great they are at their job, and how brilliantly they put out a previous fire, and this is no guarantee that they can deliver. However, if an otherwise-humble DBA looks you in the eye and says, “I can do it”, then hear them out. Sometimes, this burst of ego will be exactly what’s required.

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  • Importing PSTs with PowerShell in Exchange 2010 SP1

    Unless you use Red Gate's PST Importer, the import and export of PST files with Exchange 2010 is a complex and error-prone business. Microsoft have acknowledged this in the release of Exchange 2010 SP1, since they have now re-engineered the way that PSTs are handled to try and ease the pain of importing and exporting them, but it is still a matter of using Powershell with cmdlets, rather than a GUI. Jaap Wesselius takes a look at the new process.

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  • SQLBeat Podcast – Episode 4 – Mark Rasmussen on Machine Guns,Jelly Fish and SQL Storage Engine

    - by SQLBeat
    In this this 4th SQLBeat Podcast I talk with fellow Dane Mark Rasmussen on SQL, machine guns and jelly fish fights; apparently they are common in our homeland. Who am I kidding, I am not Danish, but I try to be in this podcast. Also, we exchange knowledge on SQL Server storage engine particulars as well as some other “internals” like password hashes and contained databases. And then it just gets weird and awesome. There is lots of background noise from people who did not realize we were recording. And I call them out and make fun of them as they deserve; well just one person who is well known in these parts. I also learn the correct (almost) pronunciation of “fjord”. Seriously, a word with an “F” followed by a “J”. And there are always the hippies and hipsters to discuss. Should be fun.

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  • An Introduction to Information Rights Management in Exchange 2010

    If you’re a Systems Administrator concerned about information security, you could do worse than implementing Microsoft’s Information Rights Management system; especially if you already have Active Directory Rights Management Services in place. Elie Bou Issa talks Hub Servers, Transport Protection Rules and Outlook integration in this excellent guide to getting started with IRM.

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  • Implementing User-Defined Hierarchies in SQL Server Analysis Services

    To be able to drill into multidimensional cube data at several levels, you must implement all of the hierarchies on the database dimensions. Then you'll create the attribute relationships necessary to optimize performance. Analysis Services hierarchies offer plenty of possibilities for displaying the data that your business requires. Rob Sheldon continues his series on SQL Server Analysis Services 2008.

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  • Understanding Performance Profiling Targets

    In this sample chapter from his upcoming book, Paul Glavich explains performance metrics and walks us through the steps needed to establish meaningful performance targets. He covers many metrics such as "time to first byte" and explains why you should add some contingency into your estimated performance requirements.

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  • Optimizing Memory Usage in a .NET Application with ANTS Memory Profiler

    Most people have encountered an OutOfMemory problem at some point or other, and these people know that tracking down the source of the problem is often a time-consuming and frustrating task. Florian Standhartinger gives us a walkthrough of how he used the ANTS Memory Profiler to help make an otherwise painful task that little bit less troublesome.

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  • SQLBeat Podcast – Episode 7 – Niko Neugebauer, Linguist, SQL MVP and Hekaton Lover

    - by SQLBeat
    In this episode of the SQLBeat Podcast I steal Niko Neugebaur away from his guarded post at the PASS Community Zone at Summit 2012 in Seattle to chat with me about several intriguing topics. Mainly we discuss Hekaton and in memory databases, languages of all sorts, Microsoft’s direction, Reporting Services and Java. Or was that Java Script? Probably best that I stick with what I know and that is SQL Server. Niko, as always, is thoughtful and straightforward, congenial and honest. I like that about him and I know you will too. Enjoy! Download the MP3

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  • Regional Office Virtualization - Less Can Be More

    The dream of an 'office in a box' has been around for years, but the increasing sophistication of virtualization software has turned the dream into reality. Ben Lye explains the problems and benefits of reducing the amount of physical hardware that were deployed in his organisation's regional offices.

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  • New Wine in New Bottles

    - by Tony Davis
    How many people, when their car shows signs of wear and tear, would consider upgrading the engine and keeping the shell? Even if you're cash-strapped, you'll soon work out the subtlety of the economics, the cost of sudden breakdowns, the precious time lost coping with the hassle, and the low 'book value'. You'll generally buy a new car. The same philosophy should apply to database systems. Mainstream support for SQL Server 2005 ends on April 12; many DBAS, if they haven't done so already, will be considering the migration to SQL Server 2008 R2. Hopefully, that upgrade plan will include a fresh install of the operating system on brand new hardware. SQL Server 2008 R2 and Windows Server 2008 R2 are designed to work together. The improved architecture, processing power, and hyper-threading capabilities of modern processors will dramatically improve the performance of many SQL Server workloads, and allow consolidation opportunities. Of course, there will be many DBAs smiling ruefully at the suggestion of such indulgence. This is nothing like the real world, this halcyon place where hardware and software budgets are limitless, development and testing resources are plentiful, and third party vendors immediately certify their applications for the latest-and-greatest platform! As with cars, or any other technology, the justification for a complete upgrade is complex. With Servers, the extra cost at time of upgrade will generally pay you back in terms of the increased performance of your business applications, reduced maintenance costs, training costs and downtime. Also, if you plan and design carefully, it's possible to offset hardware costs with reduced SQL Server licence costs. In his forthcoming SQL Server Hardware book, Glenn Berry describes a recent case where he was able to replace 4 single-socket database servers with one two-socket server, saving about $90K in hardware costs and $350K in SQL Server license costs. Of course, there are exceptions. If you do have a stable, reliable, secure SQL Server 6.5 system that still admirably meets the needs of a specific business requirement, and has no security vulnerabilities, then by all means leave it alone. Why upgrade just for the sake of it? However, as soon as a system shows sign of being unfit for purpose, or is moving out of mainstream support, the ruthless DBA will make the strongest possible case for a belts-and-braces upgrade. We'd love to hear what you think. What does your typical upgrade path look like? What are the major obstacles? Cheers, Tony.

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  • The Hot-Add Memory Hogs

    - by Andrew Clarke
    One of the more difficult tasks, when virtualizing a server, is to determine the amount of memory that Hypervisor should assign to the virtual machine. This requires accurate monitoring and, because of the consequences of setting the value too low, there is a great temptation to err on the side of over-provisioning. This results in fewer guest VMs and, in fact, with more accurate memory provisioning, many virtual environments could support 30% more VMs. In order to achieve a better consolidation (aka VM density) ratio, Windows Server 2008 R2 SP1 has introduced what Microsoft calls ‘Dynamic Memory’. This means that the start-up RAM VM memory assigned to guest virtual machines can be allowed to vary according to demand, changing dynamically while the VM is running, based on the workload of applications running inside. If demand outstrips supply, then memory can be rationed according to the ‘memory weight’ assigned to the guest VM. By this mechanism, memory becomes a shared resource that can be reallocated automatically as demand patterns vary. Unlike VMWare’s Memory Overcommit technology, the sum of all the memory allocations to each virtual machine will not exceed the total memory of the host computer. This is fine for applications that are self-regulating in their demands for memory, releasing memory back into the 'pool' when not under peak load. Other applications however, such as SQL Server Standard and Enterprise, are by nature, memory hogs under high workload; they can grab hot-add memory whilst running under load and then never release it. This requires more careful setting-up and the SQLOS team have provided some guidelines from for configuring SQL Server in virtual environments. Whereas VMWare’s Memory Overcommit is well-proven in a number of different configurations, Hyper-V’s ‘Dynamic Memory’ is new. So far, the indications are that it will improve the business case for virtualizing and it is probably a far more intuitive technology for the average IT professional to grasp. It is certainly worth testing to see whether it works for you.

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