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• Welcome to Jackstown

  - by fatherjack

  I live in a small town, the population count isn't that great but let me introduce you to some of the population. We'll start with Martin the Doc, he fixes up anything that gets poorly, so much so that he could be classed as the doctor, the vet and even the garage mechanic. He's got a reputation that he can fix anything and that hasn't been proved wrong yet. He's great friends with Brian (who gets called "Brains") the teacher who seems to have a sound understanding of any topic you care to pass his way. If he isn't sure he tells you and then goes to find out and comes back with a full answer real quick. Its good to have that sort of research capability close at hand. Brains is also great at encouraging anyone who needs a bit of support to get them up to speed and working on their jobs. Steve sees Brains regularly, that's because he is the librarian, he keeps all sorts of reading material and nowadays there's even video to watch about any topic you like. Steve keeps scouring all sorts of places to get the content that's needed and he keeps it in good order so that what ever is needed can be found quickly. He also has to make sure that old stuff gets marked as probably out of date so that anyone reading it wont get mislead. Over the road from him is Greg, he's the town crier. We don't have a newspaper here so Greg keeps us all informed of what's going on "out of town" - what new stuff we might make use of and what wont work in a small place like this. If we are interested he goes ahead and gets people in to demonstrate their products  and tell us about the details. Greg is pretty good at getting us discounts too. Now Greg's brother Ian works for the mayors office in the "waste management department" nowadays its all about the recycling but he still has to make sure that the stuff that cant be used any more gets disposed of properly. It depends on the type of waste he's dealing with that decides how it need to be treated and he has to know a lot about the different methods and when to use which ones. There are two people that keep the peace in town, Brent is the detective, investigating wrong doings and applying justice where necessary and Bart is the diplomat who smooths things over when any people have a dispute or disagreement. Brent is meticulous in his investigations and fair in the way he handles any situation he finds. Discretion is his byword. There's a rumour that Bart used to work for the United Nations but what ever his history there is no denying his ability to get apparently irreconcilable parties working together to their combined benefit. Someone who works closely with Bart is Brad, he is the translator in town. He has several languages that he can converse in but he can also explain things from someone's point of view or  and make it understandable to someone else. To keep things on the straight and narrow from a legal perspective is Ben the solicitor, making sure we all abide by the rules.Two people who make for an interesting evening's conversation if you get them together are Aaron and Grant, Aaron is the local planning inspector and Grant is an inventor of some reputation. Anything being constructed around here needs Aarons agreement. He's quite flexible in his rules though; if you can justify what you want to do with solid logic but he wont stand for any development going on without his inclusion. That gets a demolition notice and there's no argument. Grant as I mentioned is the inventor in town, if something can be improved or created then Grant is your man. He mainly works on his own but isnt averse to getting specific advice and assistance from specialist from out of town if they can help him finish his creations.There aren't too many people left for you to meet in the town, there's Rob, he's an ex professional sportsman. He played Hockey, Football, Cricket, you name it. He was in his element as goal keeper / wicket keeper and that shows in his personal life. He just goes about his business and people often don't even know that he's helped them. Really low profile, doesn't get any glory but saves people from lots of problems, even disasters on occasion. There goes Neil, he's a bit of an odd person, some people say he's gifted with special clairvoyant powers, personally I think he's got his ear to the ground and knows where to find out the important news as soon as its made public. Anyone getting a visit from Neil is best off to follow his advice though, he's usually spot on and you wont be caught by surprise if you follow his recommendations – wherever it comes from.Poor old Andrew is the last person to introduce you to. Andrew doesn't show himself too often but when he does it seems that people find a reason to blame him for their problems, whether he had anything to do with their predicament or not. In all honesty, without fail, and to his great credit, he takes it in good grace and never retaliates or gets annoyed when he's out and about.  It pays off too as its very often the case that those who were blaming him recently suddenly find they need his help and they readily forget the issues pretty rapidly.And then there's me, what do I do in town? Well, I'm just a DBA with a lot of hats. (Jackstown Pop. 1)

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• Microsoft Hyper-V Networking and Configuration - Part 1

  In the first of a series of articles on Hyper-V Networking, Nirmal explains Hyper-V networking and VLAN tagging, and shows how to set up a Virtual Network switch. Once this is done, the Hyper-V Virtual Network Switches can be used to connect unlimited no. of Virtual Machines.

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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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• The emergence of Atlassian's Bamboo (and a free SQL Source Control license offer!)

  - by David Atkinson

  The rise in demand for database continuous integration has forced me to skill-up in various new tools and technologies, particularly build servers. We have been using JetBrain's TeamCity here at Red Gate for a couple of years now, having replaced the ageing CruiseControl.NET, so it was a natural choice for us to use this for our database CI demos. Most of our early adopter customers have also transitioned away from CruiseControl, the majority to TeamCity and Microsoft's TeamBuild. However, more recently, for reasons we've yet to fully comprehend, we've observed a significant surge in the number of evaluators for Atlassian's Bamboo. I installed this a couple of weeks back to satisfy myself that it works seamlessly with Red Gate tools. As you would expect Bamboo's UI has the same clean feel found in any Atlassian tool (we use JIRA extensively here at Red Gate). In the coming weeks I will post a short step-by-step guide to setting up SQL Server continuous integration using the Red Gate command lines. To help us further optimize the integration between these tools I'd be very keen to hear from any Bamboo users who also use Red Gate tools who might be willing to participate in usability tests and other similar research in exchange for Amazon vouchers. If you are interested in helping out please contact me at David dot Atkinson at red-gate.com I recently spoke with Sarah, the product marketing manager for Bamboo, and we ended up having a detailed conversation about database CI, which has been meticulously documented in the form of a blog post on Atlassian's website: http://blogs.atlassian.com/2012/05/database-continuous-integration-redgate/ We've also managed to persuade Red Gate marketing to provide a great free-tool offer, provide a free SQL Source Control or SQL Connect license to Atlassian users provided it is claimed before the end of June! Full details are at the bottom of the post. Technorati Tags: sql server

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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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• 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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• 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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• 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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• 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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• SortedDictionary and SortedList

  - by Simon Cooper

  Apart from Dictionary<TKey, TValue>, there's two other dictionaries in the BCL - SortedDictionary<TKey, TValue> and SortedList<TKey, TValue>. On the face of it, these two classes do the same thing - provide an IDictionary<TKey, TValue> interface where the iterator returns the items sorted by the key. So what's the difference between them, and when should you use one rather than the other? (as in my previous post, I'll assume you have some basic algorithm & datastructure knowledge) SortedDictionary We'll first cover SortedDictionary. This is implemented as a special sort of binary tree called a red-black tree. Essentially, it's a binary tree that uses various constraints on how the nodes of the tree can be arranged to ensure the tree is always roughly balanced (for more gory algorithmical details, see the wikipedia link above). What I'm concerned about in this post is how the .NET SortedDictionary is actually implemented. In .NET 4, behind the scenes, the actual implementation of the tree is delegated to a SortedSet<KeyValuePair<TKey, TValue>>. One example tree might look like this: Each node in the above tree is stored as a separate SortedSet<T>.Node object (remember, in a SortedDictionary, T is instantiated to KeyValuePair<TKey, TValue>): class Node { public bool IsRed; public T Item; public SortedSet<T>.Node Left; public SortedSet<T>.Node Right; } The SortedSet only stores a reference to the root node; all the data in the tree is accessed by traversing the Left and Right node references until you reach the node you're looking for. Each individual node can be physically stored anywhere in memory; what's important is the relationship between the nodes. This is also why there is no constructor to SortedDictionary or SortedSet that takes an integer representing the capacity; there are no internal arrays that need to be created and resized. This may seen trivial, but it's an important distinction between SortedDictionary and SortedList that I'll cover later on. And that's pretty much it; it's a standard red-black tree. Plenty of webpages and datastructure books cover the algorithms behind the tree itself far better than I could. What's interesting is the comparions between SortedDictionary and SortedList, which I'll cover at the end. As a side point, SortedDictionary has existed in the BCL ever since .NET 2. That means that, all through .NET 2, 3, and 3.5, there has been a bona-fide sorted set class in the BCL (called TreeSet). However, it was internal, so it couldn't be used outside System.dll. Only in .NET 4 was this class exposed as SortedSet. SortedList Whereas SortedDictionary didn't use any backing arrays, SortedList does. It is implemented just as the name suggests; two arrays, one containing the keys, and one the values (I've just used random letters for the values): The items in the keys array are always guarenteed to be stored in sorted order, and the value corresponding to each key is stored in the same index as the key in the values array. In this example, the value for key item 5 is 'z', and for key item 8 is 'm'. Whenever an item is inserted or removed from the SortedList, a binary search is run on the keys array to find the correct index, then all the items in the arrays are shifted to accomodate the new or removed item. For example, if the key 3 was removed, a binary search would be run to find the array index the item was at, then everything above that index would be moved down by one: and then if the key/value pair {7, 'f'} was added, a binary search would be run on the keys to find the index to insert the new item, and everything above that index would be moved up to accomodate the new item: If another item was then added, both arrays would be resized (to a length of 10) before the new item was added to the arrays. As you can see, any insertions or removals in the middle of the list require a proportion of the array contents to be moved; an O(n) operation. However, if the insertion or removal is at the end of the array (ie the largest key), then it's only O(log n); the cost of the binary search to determine it does actually need to be added to the end (excluding the occasional O(n) cost of resizing the arrays to fit more items). As a side effect of using backing arrays, SortedList offers IList Keys and Values views that simply use the backing keys or values arrays, as well as various methods utilising the array index of stored items, which SortedDictionary does not (and cannot) offer. The Comparison So, when should you use one and not the other? Well, here's the important differences: Memory usage SortedDictionary and SortedList have got very different memory profiles. SortedDictionary... has a memory overhead of one object instance, a bool, and two references per item. On 64-bit systems, this adds up to ~40 bytes, not including the stored item and the reference to it from the Node object. stores the items in separate objects that can be spread all over the heap. This helps to keep memory fragmentation low, as the individual node objects can be allocated wherever there's a spare 60 bytes. In contrast, SortedList... has no additional overhead per item (only the reference to it in the array entries), however the backing arrays can be significantly larger than you need; every time the arrays are resized they double in size. That means that if you add 513 items to a SortedList, the backing arrays will each have a length of 1024. To conteract this, the TrimExcess method resizes the arrays back down to the actual size needed, or you can simply assign list.Capacity = list.Count. stores its items in a continuous block in memory. If the list stores thousands of items, this can cause significant problems with Large Object Heap memory fragmentation as the array resizes, which SortedDictionary doesn't have. Performance Operations on a SortedDictionary always have O(log n) performance, regardless of where in the collection you're adding or removing items. In contrast, SortedList has O(n) performance when you're altering the middle of the collection. If you're adding or removing from the end (ie the largest item), then performance is O(log n), same as SortedDictionary (in practice, it will likely be slightly faster, due to the array items all being in the same area in memory, also called locality of reference). So, when should you use one and not the other? As always with these sort of things, there are no hard-and-fast rules. But generally, if you: need to access items using their index within the collection are populating the dictionary all at once from sorted data aren't adding or removing keys once it's populated then use a SortedList. But if you: don't know how many items are going to be in the dictionary are populating the dictionary from random, unsorted data are adding & removing items randomly then use a SortedDictionary. The default (again, there's no definite rules on these sort of things!) should be to use SortedDictionary, unless there's a good reason to use SortedList, due to the bad performance of SortedList when altering the middle of the collection.

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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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• 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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• Video games, content strategy, and failure - oh my.

  - by Roger Hart

  Last night was the CS London group's event Content Strategy, Manhattan Style. Yes, it's a terrible title, feeling like a self-conscious grasp for chic, sadly commensurate with the venue. Fortunately, this was not commensurate with the event itself, which was lively, relevant, and engaging. Although mostly if you're a consultant. This is a strong strain in current content strategy discourse, and I think we're going to see it remedied quite soon. Not least in Paris on Friday. A lot of the bloggers, speakers, and commentators in the sphere are consultants, or part of agencies and other consulting organisations. A lot of the talk is about how you sell content strategy to your clients. This is completely acceptable. Of course it is. And it's actually useful if that's something you regularly have to do. To an extent, it's even portable to those of us who have to sell content strategy within an organisation. We're still competing for credibility and resource. What we're doing less is living in the beginning of a project. This was touched on by Jeffrey MacIntyre (albeit in a your-clients kind of a way) who described "the day two problem". Companies, he suggested, build websites for launch day, and forget about the need for them to be ongoing entities. Consultants, agencies, or even internal folks on short projects will live through Day Two quite often: the trainwreck moment where somebody realises that even if the content is right (which it often isn't), and on time (which it often isn't), it'll be redundant, outdated, or inaccurate by the end of the week/month/fickle social media attention cycle. The thing about living through a lot of Day Two is that you see a lot of failure. Nothing succeeds like failure? Failure is good. When it's structured right, it's an awesome tool for learning - that's kind of how video games work. I'm chewing over a whole blog post about this, but basically in game-like learning, you try, fail, go round the loop again. Success eventually yields joy. It's a relatively well-known phenomenon. It works best when that failing step is acutely felt, but extremely inexpensive. Dying in Portal is highly frustrating and surprisingly characterful, but the save-points are well designed and the reload unintrusive. The barrier to re-entry into the loop is very low, as is the cost of your failure out in meatspace. So it's easy (and fun) to learn. Yeah, spot the difference with business failure. As an external content strategist, you get to rock up with a big old folder full of other companies' Day Two (and ongoing day two hundred) failures. You can't send the client round the learning loop - although you may well be there because they've been round it once - but you can show other people's round trip. It's not as compelling, but it's not bad. What about internal content strategists? We can still point to things that are wrong, and there are some very compelling tools at our disposal - content inventories, user testing, and analytics, for instance. But if we're picking up big organically sprawling legacy content, Day Two may well be a distant memory, and the felt experience of web content failure is unlikely to be immediate to many people in the organisation. What to do? My hunch here is that the first task is to create something immediate and felt, but that it probably needs to be a success. Something quickly doable and visible - a content problem solved with a measurable business result. Now, that's a tall order; but scrape of the "quickly" and it's the whole reason we're here. At Red Gate, I've started with the text book fear and passion introduction to content strategy. In fact, I just typo'd that as "contempt strategy", and it isn't a bad description. Yelling "look at this, our website is rubbish!" gets you the initial attention, but it doesn't make you many friends. And if you don't produce something pretty sharp-ish, it's easy to lose the momentum you built up for change. The first thing I've done - after the visual content inventory - is to delete a bunch of stuff. About 70% of the SQL Compare web content has gone, in fact. This is a really, really cheap operation. It's visible, and it's powerful. It's cheap because you don't have to create any new content. It's not free, however, because you do have to validate your deletions. This means analytics, actually reading that content, and talking to people whose business purposes that content has to serve. If nobody outside the company uses it, and nobody inside the company thinks they ought to, that's a no-brainer for the delete list. The payoff here is twofold. There's the nebulous hard-to-illustrate "bad content does user experience and brand damage" argument; and there's the "nobody has to spend time (money) maintaining this now" argument. One or both are easily felt, and the second at least should be measurable. But that's just one approach, and I'd be interested to hear from any other internal content strategy folks about how they get buy-in, maintain momentum, and generally get things done.

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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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• Curing the Database-Application mismatch

  - by Phil Factor

  If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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• .NET Reflector Pro to the rescue

  Almost all applications have to interface with components or modules written by somebody else, for which you don't have the source code. This is fine until things go wrong, but when you need to refactor your code and you keep getting strange exceptions, you'll start to wish you could place breakpoints in someone else's code and step through it. Now, of course, you can, as Geoffrey Braaf discovered.

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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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• 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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• 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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• 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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• Win a copy of ANTS Memory Profiler!

  - by Bart Read

  Tell us about your experiences dealing with memory issues in .NET, and you stand a chance of winning a copy of the best memory profiler out there....(read more)

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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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• 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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• 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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