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• Experience vs. versatility

  - by Florin Bombeanu

  Let's say a .NET programmer works at a company which provides software on demand, not as a product. The programmer works in WPF for a period of time and he/she invests lots of time in it. He/she get very good at WPF and Windows Forms and desktop development in general. But the company has to provide a web application now, so the developer has to learn MVC or Web Forms. He/she is not experienced in web development so he/she starts investing time in this new technology and in time they get good at it. But this time the company has to provide a Sharepoint solution, and so on. What is more important: Being very very good at a certain technology, Or be as versatile as possible knowing less in each technology but covering a greater area of expertise? Should the programmer keep studying and working in WPF until he/she reaches a guru level or is it a good thing that they had to learn other technologies as well? I agree with those of you who will say that when learning different technologies you will also learn things which are useful no matter the technology you're programming in. But eventually, when the programmer will want to change jobs, will it matter more that he/she knows some WPF, MVC or Sharepoint than the fact that he/she is insanely good at one of them? I would think the second one is more important since most companies are looking for a developer for a certain technology. I don't think there are many companies looking for technical know-it-all people. What do you think?

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• What is the best drink to drink when you have read nonsense questions on programmers?

  - by stefan

  I am having a hard time deciding what drink to drink after I have read a nonsense question on programmers.stackexchange. It's either Beer och Whisky; The beer is nice since you can down it some what relaxed but some times I feel the need for something "stronger" because the question is so utterly nonsense and stupid. Every time I have read a stupid / nonsense question on programmers.stackexchange.com I've questioned myself why I didnt write some code instead. I couldve probably written countless lines of codes, together probably building a new Facebook or Linux by now. But instead I sacrificed my precious time reading questions that shouldn't have been posted on the internet. It really makes me frustrating, I guess that is why I am so often considering the whisky part instead of beer. Since beer will maybe not calm me down enough and then I have to take the whisky too, together it's a) slightly more expensive and b) more time consuming. So, what is the best drink?

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• Using machine learning to aim mirrors in a solar array?

  - by Buttons840

  I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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• Career Advice: finding challenging work in software and web development

  - by dianovich

  Having left my physics degree early, I started out in the realm of web design / front end web development and was able to get work quite quickly. I moved on to spend a chunk of my time on servers and gained experience with frameworks like Wordpress and Drupal, then the likes of Codeigniter and CakePHP and became comfortable in Debian-based and RHEL/CentOS environments. I ventured in to iOS development and published a couple of native apps to the app store too! I have started to spend a good deal of my time writing Python and have invested a little time in Django. The problem is, I still spend a fair chunk of my time doing more front end web development (writing markup and CSS for site themes, design-lead JavaScript, small applications for which application architecture and software engineering are relatively unimportant or too time consuming to invest in) in my job. What I want to do is really exercise the systematic/logical portion of my brain and tackle challenging problems on a daily basis. I want to have to care about big-oh running times, modularity in software, DRY, performance tuning and development methodologies. I want to work for a firm whose clients say: "Yes, these things are important to us and we'll pay you to get them right." But it is difficult: I have no formal training and am potentially becoming a jack of all trades. Not that being a jack of many trades is necessarily a bad thing, but the scope of work I find myself involved in is far too broad. And, there are only so many hours in a day outside of work! My question is: where do I go from here? I am starting to work on a few open source projects and have started to publish content to my blog. But this isn't likely to make it past the recruitment consultants and HR departments of many-a-firm. And I do not, for example, work in a team that practices agile methodologies, so how do I get work in such a team to gain experience? While I have been responsible for implementing version control and some solid working practices into our current environment, there is only so far I can go in this context. What would convince you that i'm worth taking a risk? What would convince you that i'll have caught up the other guys in your employ in next to no time?

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• Sounds to describe the weather?

  - by Matthew

  I'm trying to think of sounds that will help convey the time of day and weather condition. I'm not even sure of all the weather conditions I would consider, and some are obvious. Like if it's raining, the sound of rain. But then I'm thinking, what about for a calm day? If it's morning time, I could do birds chirping or something. Night time could be an owl or something. What are some good combinations of sounds/weather/time to have a good effect?

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• Subterranean IL: Generics and array covariance

  - by Simon Cooper

  Arrays in .NET are curious beasts. They are the only built-in collection types in the CLR, and SZ-arrays (single dimension, zero-indexed) have their own commands and IL syntax. One of their stranger properties is they have a kind of built-in covariance long before generic variance was added in .NET 4. However, this causes a subtle but important problem with generics. First of all, we need to briefly recap on array covariance. SZ-array covariance To demonstrate, I'll tweak the classes I introduced in my previous posts: public class IncrementableClass { public int Value; public virtual void Increment(int incrementBy) { Value += incrementBy; } } public class IncrementableClassx2 : IncrementableClass { public override void Increment(int incrementBy) { base.Increment(incrementBy); base.Increment(incrementBy); } } In the CLR, SZ-arrays of reference types are implicitly convertible to arrays of the element's supertypes, all the way up to object (note that this does not apply to value types). That is, an instance of IncrementableClassx2[] can be used wherever a IncrementableClass[] or object[] is required. When an SZ-array could be used in this fashion, a run-time type check is performed when you try to insert an object into the array to make sure you're not trying to insert an instance of IncrementableClass into an IncrementableClassx2[]. This check means that the following code will compile fine but will fail at run-time: IncrementableClass[] array = new IncrementableClassx2[1]; array[0] = new IncrementableClass(); // throws ArrayTypeMismatchException These checks are enforced by the various stelem* and ldelem* il instructions in such a way as to ensure you can't insert a IncrementableClass into a IncrementableClassx2[]. For the rest of this post, however, I'm going to concentrate on the ldelema instruction. ldelema This instruction pops the array index (int32) and array reference (O) off the stack, and pushes a pointer (&) to the corresponding array element. However, unlike the ldelem instruction, the instruction's type argument must match the run-time array type exactly. This is because, once you've got a managed pointer, you can use that pointer to both load and store values in that array element using the ldind* and stind* (load/store indirect) instructions. As the same pointer can be used for both input and output to the array, the type argument to ldelema must be invariant. At the time, this was a perfectly reasonable restriction, and maintained array type-safety within managed code. However, along came generics, and with it the constrained callvirt instruction. So, what happens when we combine array covariance and constrained callvirt? .method public static void CallIncrementArrayValue() { // IncrementableClassx2[] arr = new IncrementableClassx2[1] ldc.i4.1 newarr IncrementableClassx2 // arr[0] = new IncrementableClassx2(); dup newobj instance void IncrementableClassx2::.ctor() ldc.i4.0 stelem.ref // IncrementArrayValue<IncrementableClass>(arr, 0) // here, we're treating an IncrementableClassx2[] as IncrementableClass[] dup ldc.i4.0 call void IncrementArrayValue<class IncrementableClass>(!!0[],int32) // ... ret } .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } And the result: Unhandled Exception: System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array. at IncrementArrayValue[T](T[] arr, Int32 index) at CallIncrementArrayValue() Hmm. We're instantiating the generic method as IncrementArrayValue<IncrementableClass>, but passing in an IncrementableClassx2[], hence the ldelema instruction is failing as it's expecting an IncrementableClass[]. On features and feature conflicts What we've got here is a conflict between existing behaviour (ldelema ensuring type safety on covariant arrays) and new behaviour (managed pointers to object references used for every constrained callvirt on generic type instances). And, although this is an edge case, there is no general workaround. The generic method could be hidden behind several layers of assemblies, wrappers and interfaces that make it a requirement to use array covariance when calling the generic method. Furthermore, this will only fail at runtime, whereas compile-time safety is what generics were designed for! The solution is the readonly. prefix instruction. This modifies the ldelema instruction to ignore the exact type check for arrays of reference types, and so it lets us take the address of array elements using a covariant type to the actual run-time type of the array: .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 readonly. ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } But what about type safety? In return for ignoring the type check, the resulting controlled mutability pointer can only be used in the following situations: As the object parameter to ldfld, ldflda, stfld, call and constrained callvirt instructions As the pointer parameter to ldobj or ldind* As the source parameter to cpobj In other words, the only operations allowed are those that read from the pointer; stind* and similar that alter the pointer itself are banned. This ensures that the array element we're pointing to won't be changed to anything untoward, and so type safety within the array is maintained. This is a typical example of the maxim that whenever you add a feature to a program, you have to consider how that feature interacts with every single one of the existing features. Although an edge case, the readonly. prefix instruction ensures that generics and array covariance work together and that compile-time type safety is maintained. Tune in next time for a look at the .ctor generic type constraint, and what it means.

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• Are Google Maps Open?

  - by EmbeddedInsider

  Right now they are ‘free’ but it is clear what the path forward is:   4.3 Advertising. The Service currently does not include advertising in the maps images. However, Google reserves the right to include advertising in the maps images provided to you through the Service, but will provide you with ninety (90) days notice prior to the commencement of advertising in the maps images. Such notice may be provided on relevant Google websites, including but not limited to the Google Geo Developers Blog and the Google Maps API Group (or such successor URLs that Google may designate from time to time). During that 90 day period, you may terminate your use of the Service, or provide notice of your refusal to accept advertising in the maps images in accordance with Google's policies and procedures for providing such notice (which Google may make available from time to time in its sole discretion). Lawrence Ricci www.EmbeddedInsider.com

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• asus n550jv audio problem: no sound from notebook' speakers

  - by skywalker

  Ubuntu 13.10. The problem is: the internal speakers don't work. I have no problem when I'm using the headphones. There is no hardware issue since in windows 8 everything works perfectly(external subwoofer included). I'm trying to modify /etc/modprobe.d/alsa-base.conf but I can't find the correct model to put into: options snd-hda-intel model= The file HD-Audio-Models.txt doesn't contain the model for ALC668. Some info: :~sudo aplay -l **** List of PLAYBACK Hardware Devices **** card 0: MID [HDA Intel MID], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: MID [HDA Intel MID], device 7: HDMI 1 [HDMI 1] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: MID [HDA Intel MID], device 8: HDMI 2 [HDMI 2] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: PCH [HDA Intel PCH], device 0: ALC668 Analog [ALC668 Analog] Subdevices: 0/1 Subdevice #0: subdevice #0 :~$ sudo lspci -v | grep -A7 -i "audio" 00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06) Subsystem: Intel Corporation Device 2010 Flags: bus master, fast devsel, latency 0, IRQ 52 Memory at f7a14000 (64-bit, non-prefetchable) [size=16K] Capabilities: [50] Power Management version 2 Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit- Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00 Kernel driver in use: snd_hda_intel -- 00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 04) Subsystem: ASUSTeK Computer Inc. Device 11cd Flags: bus master, fast devsel, latency 0, IRQ 53 Memory at f7a10000 (64-bit, non-prefetchable) [size=16K] Capabilities: [50] Power Management version 2 Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+ Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00 Capabilities: [100] Virtual Channel PS info :~$ amixer -c 0 Simple mixer control 'IEC958',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'IEC958',1 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'IEC958',2 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] :~$ pacmd dump-volumes Welcome to PulseAudio! Use "help" for usage information. Sink 0: reference = 0: 76% 1: 76%, real = 0: 76% 1: 76%, soft = 0: 100% 1: 100%, current_hw = 0: 76% 1: 76%, save = yes Input 8: volume = 0: 100% 1: 100%, reference_ratio = 0: 100% 1: 100%, real_ratio = 0: 100% 1: 100%, soft = 0: 100% 1: 100%, volume_factor = 0: 100% 1: 100%, volume_factor_sink = 0: 100% 1: 100%, save = no Source 0: reference = 0: 100% 1: 100%, real = 0: 100% 1: 100%, soft = 0: 100% 1: 100%, current_hw = 0: 100% 1: 100%, save = no Source 1: reference = 0: 16% 1: 16%, real = 0: 16% 1: 16%, soft = 0: 100% 1: 100%, current_hw = 0: 16% 1: 16%, save = yes

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• Is software innovation still primarily North American and European? Why, and for how much longer?

  - by limist

  Since this site is read by a global audience of programmers, I want to know if people generally agree that the vast majority of software innovation - languages, OS, tools, methodologies, books, etc. - still originates from the USA, Canada, and the EU. I can think of a few exceptions, e.g. Nginx webserver from Russia and the Ruby language from Japan, but overwhelmingly, the software I use and encounter daily is from North America and the EU. Why? Is history and historical momentum (computing having started in USA and Europe) still driving the industry? And/or, is some nebulous (or real) cultural difference discouraging software innovation abroad? Or are those of us in the West simply ignorant of real software innovation going on in Asia, South America, Eastern Europe, etc.? When, if ever, might the centers of innovation move out of the West? Your experiences and opinions welcome, thanks!

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• Walmart and Fusion Apps

  - by ultan o'broin

  Photograph: Misha Vaughan I attended Fusion Apps (yes, I know I am supposed to say "Oracle Fusion Applications", but stuffy old style guides are a turn-off in interwebs conversations) User Experience Advocate (FXA) training in Long Beach, California last week; a suitable location as ODTUG KSCOPE 11 was kicking off and key players were in the area. As a member of Oracle's Apps-UX team I know the Fusion Apps messaging, natch, and done some other Fusion Apps go-to-market content work too. For the messaging details themselves, see Lonneke Dikmans (@lonnekedikmans) great blog, by the way. However, I wanted some 'formal' training combined with the opportunity to meet and learn from people already out there delivering those messages. The idea in me reaching out to Misha Vaughan, Apps-UX FXA maven, to get me onto this training was that in addition to my UX knowledge, I could leverage my location in EMEA and hit up customer events more quickly and easily. Those local user groups do like to hear the voice of locals too you know (so I need to work on that mid-Atlantic accent). I'm looking forward to such opportunities. The training was all smashing stuff, just the right level of detail, delivered professionally and with great style and humor. I was especially honored to be paired off for my er, coaching with Debra Lilley (@debralilley), who shared with everyone all kinds of tips and insights from her experiences of delivering the message and demo. For me, that was the real power of the FXA event--the communal, conversational aspect--the meeting up with people who had done all this for real, the sharing in their experiences, while learning along with other newbies. Sorry, but that all-important social aspect doesn't work so well with remote meetings. Katie Candland (Apps-UX) gave us a great tour of the Fusion Apps demo and included some useful presentational tips too (any excuse to buy that iPad). It's clear to me that the Fusion Apps messaging and demos really come alive with real-world examples that local application users will recognize, and I picked up some "yes, that's my job made easier" scene-stealers from Debra and Karen Brownfield too, to add to the great ones already provided. This power of examples shouldn't surprise anyone, they've long been a mainstay of applications user assistance, popular with users. We'll offer customers different types of example topics in the Fusion Apps online help too (stay tuned), and we know from research how important those 3S's (stories, scenarios, and simulations) are to users when they consume and apply information. Well, we've got the simulation, now it's time for more stories and scenarios. If you get a chance to participate in an FXA event (whether you are an Oracle employee or otherwise), I'd encourage it. It's committing your time and energy for sure, but I got real bang for the buck from it for my everyday job too. Listening to the room's feedback on the application demo really brought our internal design work to life, and I picked up on some things that I need to follow up on (like how you alphabetically sort stuff in other languages). User experience is after all, about users. What will I be doing next, and what would I like to see happen? Obviously, I need to develop my story-telling links with the people I met in Long Beach and do some practicing with the materials, and then get out there and deliver them at a suitable location. The demo is what it is right now, and that's a super-rich demo that I know everyone will want to see and ask questions about. Then, as mentioned by attendees at the FXA event, follow up on those translated and localized messages for EMEA (and APAC), that deal with different statutory or reporting requirements of the target markets. Given my background I would say that, wouldn't I? However, language is part of the UX, and international revenue is greater than US-only revenue for Oracle, so yes dear, we all need to get over the fact that enterprise apps users don't all speak, or want to speak, American-English. Most importantly perhaps, the continued development of a strong messaging community between Oracle and partners and customers where we can swap and share those FXA messaging stories and scenarios about Fusion Apps in a conversational way. The more the better, a combination of online and face-to-face meetings. I must also mention the great dinner after the event at Parker's Lighthouse, and the fun myself and Andrew Gilmour (Apps-UX) had at our end of the table talking about just about everything except Fusion Apps with Ronald Van Luttikhuizen and Ben Prusinski (who now understands the difference between Cork and Dublin people. I hope). Thanks to all the Apps-UXers who helped bring the FXA training to town, and to Debra and all the others that I am too jetlagged to mention right who were instrumental in making it happen for me. Here's to the next one. And the Walmart angle? That was me doing my Robert Scoble (ScO'bilizer?)-style guerilla smart phone research in Walmart in Long Beach, before the FXA event. It's all about stories for me. You can read more about it on the appslab blog (see the comments).

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• I don't understand why algorithms are so special

  - by Jessica

  I'm a student of computer science trying to soak up as much information on the topic as I can during my free time. I keep returning to algorithms time and again in various formats (online course, book, web tutorial), but the concept fails to sustain my attention. I just don't understand: why are algorithms so special? I can tell you why fractals are awesome, why the golden ratio is awesome, why origami is awesome and scientific applications of all the above. Heck I even love Newton's laws and conical sections. But when it comes to algorithms, I'm just not astounded. They are not insightful in new ways about human cognition at all. I was expecting algorithms to be shattering preconceptions and mind-altering but time and time again they fail miserably. What am I doing wrong in my approach? Can someone tell me why algorithms are so awesome?

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• Poor Customer Service Example

  - by MightyZot

  Lately I have been frustrated by examples of poor customer service. At least one is worth writing about because I don’t think companies realize the effects of their service policies on loyal customers. Bad Customer Service Example #1 Recently, I received an offer in the mail from my cable company, suddenLink. The offer was for an updated TiVo for $12/mo. Normally I ignore offers like this one because I already have the service they’re offering and many times advertisers are offering alternatives to what is already an excellent product offering. I tend to exhibit a high level of loyalty to the products and brands that I use. In this case, we were looking to upgrade our TiVo and this deal is attractive for several reasons: I don’t want to pay a huge amount up-front for the device, so paying a monthly amount for the device is attractive to me. My entertainment is almost all on a single invoice. I’m no longer going to be billed by suddenLink and TiVo. TiVo is still involved, so I am still loyal to the brand I love. I have resisted moving to other DVRs and services for over a decade. I called suddenLink to order the new TiVo and was rewarded with great customer service. In fact, I can’t remember ever getting poor customer service from suddenLink. They are always there to answer my technical support questions and they are very responsive to outages. Then I called TiVo. First of all, I chose the option on the phone system to change or cancel my service, which was consequently met by an inordinate hold time. (I’m calling this time inordinate because I get through very quickly if I want to purchase something.) This is a trend that I’ve noticed with companies – if you want me to be loyal to you, it should be just as easy to cancel your service as it is to purchase it. Because, I should never be cancelling because I am unhappy. And, if you ever want my business again, or more importantly a reference, then you’d better make the exit door open just as easy as the enter door. After quite some time on hold, I talked to “Victor” who was very courteous. Victor canceled my service and then told me that I could keep my current TiVo and transfer recorded programs to it from the new TiVo.  Cool I said, but what about the cost?  He said there was no extra cost.  This was also attractive to me because I paid for my TiVo and it would be good to use it for something at least.  That was four months ago. This month I noticed that TiVo was still charging me for my original service. I was a little upset, but I decided to give them the benefit of the doubt. After all, I am a loyal TiVo customer and I have resisted moving to other solutions for over a decade. I’m sure they will do whatever it takes to keep my business, through TiVo or through suddenLink. After quite some time on hold, I was able to talk to a customer service representative, “Les”. I explained that I am a loyal TiVo customer, but I purchased this deal through my cable provider. I’m still with TiVo, I just wanted a single bill and to take advantage of the pay-over-time option. “Les” told me that he was very sorry to hear that I’m leaving TiVo, to which I responded again that I wasn’t leaving TiVo, I just want one invoice, and to take advantage of the pay-over-time. So, after explaining that I requested a termination of the non-suddenLink account (TiVo can see both of course), I was put on hold again for quite some time while my refund was “approved”.  “Les” said that he could see my cancellation request back in July. Note that it is now November, so they have billed me inappropriately four times. After quite some time, he came back on the line and told me that he was able to “get me most of my money back.” He got approval to refund 90 days. Even though I requested cancellation of one of my accounts, TiVo has that cancellation request on file and they admit overbilling me, I am going to get “most” of my money back. To top this experience off, when we were ready to hang up, “Les” told me that he was sorry to see me go and that he hoped I would come back to TiVo again. Again, I explained to “Les” that I have not left TiVo. I am just paying them through suddenLink. At that point, he went into a small dissertation about how this is a special arrangement they have with suddenLink and very few others. He made me feel like I was doing something wrong. Why should I feel that way? TiVo made the deal with suddenLink, not me, and the deal seemed like a good compromise for me to be able to get what I need. Here is what TiVo Customer Service accomplished on those two calls – I no longer feel like I need to be loyal to the TiVo brand or service. If I had been treated better on these two calls, I would still be recommending TiVo to my friends. They would still be getting revenue from a loyal customer, who paid the same rate for over a decade, and this article wouldn’t be here for you to read. Interesting… In my opinion, if you want brand loyalty, be loyal to your customers!

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• Project Euler 11: (Iron)Python

  - by Ben Griswold

  In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 11.  As always, any feedback is welcome. # Euler 11 # http://projecteuler.net/index.php?section=problems&id=11 # What is the greatest product # of four adjacent numbers in any direction (up, down, left, # right, or diagonally) in the 20 x 20 grid? import time start = time.time() grid = [\ [8,02,22,97,38,15,00,40,00,75,04,05,07,78,52,12,50,77,91,8],\ [49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,04,56,62,00],\ [81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,03,49,13,36,65],\ [52,70,95,23,04,60,11,42,69,24,68,56,01,32,56,71,37,02,36,91],\ [22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80],\ [24,47,32,60,99,03,45,02,44,75,33,53,78,36,84,20,35,17,12,50],\ [32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70],\ [67,26,20,68,02,62,12,20,95,63,94,39,63,8,40,91,66,49,94,21],\ [24,55,58,05,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72],\ [21,36,23,9,75,00,76,44,20,45,35,14,00,61,33,97,34,31,33,95],\ [78,17,53,28,22,75,31,67,15,94,03,80,04,62,16,14,9,53,56,92],\ [16,39,05,42,96,35,31,47,55,58,88,24,00,17,54,24,36,29,85,57],\ [86,56,00,48,35,71,89,07,05,44,44,37,44,60,21,58,51,54,17,58],\ [19,80,81,68,05,94,47,69,28,73,92,13,86,52,17,77,04,89,55,40],\ [04,52,8,83,97,35,99,16,07,97,57,32,16,26,26,79,33,27,98,66],\ [88,36,68,87,57,62,20,72,03,46,33,67,46,55,12,32,63,93,53,69],\ [04,42,16,73,38,25,39,11,24,94,72,18,8,46,29,32,40,62,76,36],\ [20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,04,36,16],\ [20,73,35,29,78,31,90,01,74,31,49,71,48,86,81,16,23,57,05,54],\ [01,70,54,71,83,51,54,69,16,92,33,48,61,43,52,01,89,19,67,48]] # left and right max, product = 0, 0 for x in range(0,17): for y in xrange(0,20): product = grid[y][x] * grid[y][x+1] * \ grid[y][x+2] * grid[y][x+3] if product > max : max = product # up and down for x in range(0,20): for y in xrange(0,17): product = grid[y][x] * grid[y+1][x] * \ grid[y+2][x] * grid[y+3][x] if product > max : max = product # diagonal right for x in range(0,17): for y in xrange(0,17): product = grid[y][x] * grid[y+1][x+1] * \ grid[y+2][x+2] * grid[y+3][x+3] if product > max: max = product # diagonal left for x in range(0,17): for y in xrange(0,17): product = grid[y][x+3] * grid[y+1][x+2] * \ grid[y+2][x+1] * grid[y+3][x] if product > max : max = product print max print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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• Databinder.Eval using Lamda Expressions

  Using lambda expression to help with compile time checking of Eval statements

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• Solving Big Problems with Oracle R Enterprise, Part I

  - by dbayard

  Abstract: This blog post will show how we used Oracle R Enterprise to tackle a customer’s big calculation problem across a big data set. Overview: Databases are great for managing large amounts of data in a central place with rigorous enterprise-level controls.  R is great for doing advanced computations.  Sometimes you need to do advanced computations on large amounts of data, subject to rigorous enterprise-level concerns.  This blog post shows how Oracle R Enterprise enables R plus the Oracle Database enabled us to do some pretty sophisticated calculations across 1 million accounts (each with many detailed records) in minutes. The problem: A financial services customer of mine has a need to calculate the historical internal rate of return (IRR) for its customers’ portfolios.  This information is needed for customer statements and the online web application.  In the past, they had solved this with a home-grown application that pulled trade and account data out of their data warehouse and ran the calculations.  But this home-grown application was not able to do this fast enough, plus it was a challenge for them to write and maintain the code that did the IRR calculation. IRR – a problem that R is good at solving: Internal Rate of Return is an interesting calculation in that in most real-world scenarios it is impractical to calculate exactly.  Rather, IRR is a calculation where approximation techniques need to be used.  In this blog post, we will discuss calculating the “money weighted rate of return” but in the actual customer proof of concept we used R to calculate both money weighted rate of returns and time weighted rate of returns.  You can learn more about the money weighted rate of returns here: http://www.wikinvest.com/wiki/Money-weighted_return First Steps- Calculating IRR in R We will start with calculating the IRR in standalone/desktop R.  In our second post, we will show how to take this desktop R function, deploy it to an Oracle Database, and make it work at real-world scale.  The first step we did was to get some sample data.  For a historical IRR calculation, you have a balances and cash flows.  In our case, the customer provided us with several accounts worth of sample data in Microsoft Excel.      The above figure shows part of the spreadsheet of sample data.  The data provides balances and cash flows for a sample account (BMV=beginning market value. FLOW=cash flow in/out of account. EMV=ending market value). Once we had the sample spreadsheet, the next step we did was to read the Excel data into R.  This is something that R does well.  R offers multiple ways to work with spreadsheet data.  For instance, one could save the spreadsheet as a .csv file.  In our case, the customer provided a spreadsheet file containing multiple sheets where each sheet provided data for a different sample account.  To handle this easily, we took advantage of the RODBC package which allowed us to read the Excel data sheet-by-sheet without having to create individual .csv files.  We wrote ourselves a little helper function called getsheet() around the RODBC package.  Then we loaded all of the sample accounts into a data.frame called SimpleMWRRData. Writing the IRR function At this point, it was time to write the money weighted rate of return (MWRR) function itself.  The definition of MWRR is easily found on the internet or if you are old school you can look in an investment performance text book.  In the customer proof, we based our calculations off the ones defined in the The Handbook of Investment Performance: A User’s Guide by David Spaulding since this is the reference book used by the customer.  (One of the nice things we found during the course of this proof-of-concept is that by using R to write our IRR functions we could easily incorporate the specific variations and business rules of the customer into the calculation.) The key thing with calculating IRR is the need to solve a complex equation with a numerical approximation technique.  For IRR, you need to find the value of the rate of return (r) that sets the Net Present Value of all the flows in and out of the account to zero.  With R, we solve this by defining our NPV function: where bmv is the beginning market value, cf is a vector of cash flows, t is a vector of time (relative to the beginning), emv is the ending market value, and tend is the ending time. Since solving for r is a one-dimensional optimization problem, we decided to take advantage of R’s optimize method (http://stat.ethz.ch/R-manual/R-patched/library/stats/html/optimize.html). The optimize method can be used to find a minimum or maximum; to find the value of r where our npv function is closest to zero, we wrapped our npv function inside the abs function and asked optimize to find the minimum.  Here is an example of using optimize: where low and high are scalars that indicate the range to search for an answer.   To test this out, we need to set values for bmv, cf, t, emv, tend, low, and high.  We will set low and high to some reasonable defaults. For example, this account had a negative 2.2% money weighted rate of return. Enhancing and Packaging the IRR function With numerical approximation methods like optimize, sometimes you will not be able to find an answer with your initial set of inputs.  To account for this, our approach was to first try to find an answer for r within a narrow range, then if we did not find an answer, try calling optimize() again with a broader range.  See the R help page on optimize()  for more details about the search range and its algorithm. At this point, we can now write a simplified version of our MWRR function.  (Our real-world version is  more sophisticated in that it calculates rate of returns for 5 different time periods [since inception, last quarter, year-to-date, last year, year before last year] in a single invocation.  In our actual customer proof, we also defined time-weighted rate of return calculations.  The beauty of R is that it was very easy to add these enhancements and additional calculations to our IRR package.)To simplify code deployment, we then created a new package of our IRR functions and sample data.  For this blog post, we only need to include our SimpleMWRR function and our SimpleMWRRData sample data.  We created the shell of the package by calling: To turn this package skeleton into something usable, at a minimum you need to edit the SimpleMWRR.Rd and SimpleMWRRData.Rd files in the \man subdirectory.  In those files, you need to at least provide a value for the “title” section. Once that is done, you can change directory to the IRR directory and type at the command-line: The myIRR package for this blog post (which has both SimpleMWRR source and SimpleMWRRData sample data) is downloadable from here: myIRR package Testing the myIRR package Here is an example of testing our IRR function once it was converted to an installable package: Calculating IRR for All the Accounts So far, we have shown how to calculate IRR for a single account.  The real-world issue is how do you calculate IRR for all of the accounts?This is the kind of situation where we can leverage the “Split-Apply-Combine” approach (see http://www.cscs.umich.edu/~crshalizi/weblog/815.html).  Given that our sample data can fit in memory, one easy approach is to use R’s “by” function.  (Other approaches to Split-Apply-Combine such as plyr can also be used.  See http://4dpiecharts.com/2011/12/16/a-quick-primer-on-split-apply-combine-problems/). Here is an example showing the use of “by” to calculate the money weighted rate of return for each account in our sample data set.  Recap and Next Steps At this point, you’ve seen the power of R being used to calculate IRR.  There were several good things: R could easily work with the spreadsheets of sample data we were given R’s optimize() function provided a nice way to solve for IRR- it was both fast and allowed us to avoid having to code our own iterative approximation algorithm R was a convenient language to express the customer-specific variations, business-rules, and exceptions that often occur in real-world calculations- these could be easily added to our IRR functions The Split-Apply-Combine technique can be used to perform calculations of IRR for multiple accounts at once. However, there are several challenges yet to be conquered at this point in our story: The actual data that needs to be used lives in a database, not in a spreadsheet The actual data is much, much bigger- too big to fit into the normal R memory space and too big to want to move across the network The overall process needs to run fast- much faster than a single processor The actual data needs to be kept secured- another reason to not want to move it from the database and across the network And the process of calculating the IRR needs to be integrated together with other database ETL activities, so that IRR’s can be calculated as part of the data warehouse refresh processes In our next blog post in this series, we will show you how Oracle R Enterprise solved these challenges.

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• Expanding on requestaudit - Tracing who is doing what...and for how long

  - by Kyle Hatlestad

  One of the most helpful tracing sections in WebCenter Content (and one that is on by default) is the requestaudit tracing.  This tracing section summarizes the top service requests happening in the server along with how they are performing.  By default, it has 2 different rotations.  One happens every 2 minutes (listing up to 5 services) and another happens every 60 minutes (listing up to 20 services).  These traces provide the total time for all the requests against that service along with the number of requests and its average request time.  This information can provide a good start in possibly troubleshooting performance issues or tracking a particular issue.   >requestaudit/6 12.10 16:48:00.493 Audit Request Monitor !csMonitorTotalRequests,47,1,0.39009329676628113,0.21034042537212372,1>requestaudit/6 12.10 16:48:00.509 Audit Request Monitor Request Audit Report over the last 120 Seconds for server wcc-base_4444****requestaudit/6 12.10 16:48:00.509 Audit Request Monitor -Num Requests 47 Errors 1 Reqs/sec. 0.39009329676628113 Avg. Latency (secs) 0.21034042537212372 Max Thread Count 1requestaudit/6 12.10 16:48:00.509 Audit Request Monitor 1 Service FLD_BROWSE Total Elapsed Time (secs) 3.5320000648498535 Num requests 10 Num errors 0 Avg. Latency (secs) 0.3531999886035919 requestaudit/6 12.10 16:48:00.509 Audit Request Monitor 2 Service GET_SEARCH_RESULTS Total Elapsed Time (secs) 2.694999933242798 Num requests 6 Num errors 0 Avg. Latency (secs) 0.4491666555404663requestaudit/6 12.10 16:48:00.509 Audit Request Monitor 3 Service GET_DOC_PAGE Total Elapsed Time (secs) 1.8839999437332153 Num requests 5 Num errors 1 Avg. Latency (secs) 0.376800000667572requestaudit/6 12.10 16:48:00.509 Audit Request Monitor 4 Service DOC_INFO Total Elapsed Time (secs) 0.4620000123977661 Num requests 3 Num errors 0 Avg. Latency (secs) 0.15399999916553497requestaudit/6 12.10 16:48:00.509 Audit Request Monitor 5 Service GET_PERSONALIZED_JAVASCRIPT Total Elapsed Time (secs) 0.4099999964237213 Num requests 8 Num errors 0 Avg. Latency (secs) 0.051249999552965164requestaudit/6 12.10 16:48:00.509 Audit Request Monitor ****End Audit Report***** To change the default rotation or size of output, these can be set as configuration variables for the server: RequestAuditIntervalSeconds1 – Used for the shorter of the two summary intervals (default is 120 seconds)RequestAuditIntervalSeconds2 – Used for the longer of the two summary intervals (default is 3600 seconds)RequestAuditListDepth1 – Number of services listed for the first request audit summary interval (default is 5)RequestAuditListDepth2 – Number of services listed for the second request audit summary interval (default is 20) If you want to get more granular, you can enable 'Full Verbose Tracing' from the System Audit Information page and now you will get an audit entry for each and every service request.  >requestaudit/6 12.10 16:58:35.431 IdcServer-68 GET_USER_INFO [dUser=bob][StatusMessage=You are logged in as 'bob'.] 0.08765099942684174(secs) What's nice is it reports who executed the service and how long that particular request took.  In some cases, depending on the service, additional information will be added to the tracing relevant to that  service. >requestaudit/6 12.10 17:00:44.727 IdcServer-81 GET_SEARCH_RESULTS [dUser=bob][QueryText=%28+dDocType+%3cmatches%3e+%60Document%60+%29][StatusCode=0][StatusMessage=Success] 0.4696030020713806(secs) You can even go into more detail and insert any additional data into the tracing.  You simply need to add this configuration variable with a comma separated list of variables from local data to insert. RequestAuditAdditionalVerboseFieldsList=TotalRows,path In this case, for any search results, the number of items the user found is traced: >requestaudit/6 12.10 17:15:28.665 IdcServer-36 GET_SEARCH_RESULTS [TotalRows=224][dUser=bob][QueryText=%28+dDocType+%3cmatches%3e+%60Application%60+%29][Sta... I also recently ran into the case where services were being called from a client through RIDC.  All of the services were being executed as the same user, but they wanted to correlate the requests coming from the client to the ones being executed on the server.  So what we did was add a new field to the request audit list: RequestAuditAdditionalVerboseFieldsList=ClientToken And then in the RIDC client, ClientToken was added to the binder along with a unique value that could be traced for that request.  Now they had a way of tracing on both ends and identifying exactly which client request resulted in which request on the server.

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• An Oracle's Interns Story by Samarth Varshney

  - by user769227

  I have written a short write-up about my experience at Oracle and am attaching some pics along:  I joined Oracle on 5th January 2011 as part of my internship program in BITS Pilani Goa Campus. In the short period of six months, I had the most beautiful and interesting time of my life. It was fun to work in Oracle, thanks to the whole team. I had an excellent manager, simple and sophisticated, who gave me the utmost enthusiasm to work. I gained a lot of knowledge during my internship, thanks to my colleagues. They were very helpful and motivated us (interns) in every possible way. In the initial stages of work, in which you know almost nothing, they helped me gain knowledge at a rapid speed. Thanks to the vast database of study material at the Oracle site, that I could start on with my project in a very short time.  For me, the time flew like anything and made the 6 months look like a few days. It was probably due to the team, that the work was so much fun. We had our deadlines but had full freedom as to how to work and when to work. I don't remember a single instance, in which I was working and not listening to songs. I mean it will always be a time to remember. I hope to join this company and make this time last forever.  Samarth 

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• Be aware of the difference between CURRENT_DATE and SYSDATE

  - by Kevin Smith

  I was running some queries in SQL Developer against the WebCenter Content (WCC) schema that included date fields such as dInDate. I was comparing the dates against CURRENT_DATE. I was not getting the expected results. I did some googlng and didn’t find a solution, but I did run across a reference to SYSDATE. I tried SYSDATE in my queries and got the expected results. I did a TO_CHAR on the two date fields and found they returned different times. CURRENT_DATE returned the time from my laptop which was  in the EDT time zone. SYSDATE returned the time from the database server which happened to be in the PDT time zone. I guess if both the database server and my laptop were in the same time zone I would not have seen any problem. Here is the query I ran to display the two fields. select to_char(current_date,'DD-MON-YY HH:MI:SS'), to_char(sysdate,'DD-MON-YY HH:MI:SS') from dual; As you can see from the screen shot from SQL Developer they definitely returned different times. I’m sure there is some command or setting you can use to prevent this problem, but for me the take away is to use SYSDATE in your queries when you want to do any date comparison.

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• How Estimates Became Quotes

  - by Lee Brandt

  It’s our fault. Well, not completely, but we haven’t helped the situation any. All of what follows comes from my own experiences which, from talking to lots of other developers about it, seems to be pretty much par for the course. Where We Started When we first started estimating, we estimated pretty clearly. We would try to imagine something we’d done that was similar to the project being estimated and we’d toss it about in our heads a bit and see how much bigger or smaller we thought this new thing was, and add or subtract accordingly. We wouldn’t spend too much time on it, because we wanted to get to writing the software. Eventually, we’d come across some huge problem that there was now way we could’ve known about ahead of time. Either we didn’t see this thing or, we didn’t realize that this particular version of a problem would be so… problematic. We usually call this “not knowing what we don’t know”. It’s unavoidable. We just can’t know. Until we wade in and start putting some code together, there are just some things we won’t know… and some things we don’t even know that we don’t know. Y’know? So what happens? We go over budget. Project managers scream and dance the dance of the stressed-out project manager, and there is nothing we can do (or could’ve done) about it. We didn’t know. We thought about it for a bit and we didn’t see this herculean task sitting in the middle of our nice quiet project, and it has bitten us in the rear end. We now know how to handle this in the future, though. We will take some more time to pick around the requirements and discover all those things we don’t know. We’ll do some prototyping, we’ll read some blogs about similar projects, we’ll really grill the customer with questions during the requirements gathering phase. We’ll keeping asking “what else?” until the shove us down the stairs. We’ll take our time and uncover it all. We Learned, But Good The next time comes, and you know what happens? We do it. We grill the customer for weeks and prototype and read and research and we estimate everything down to the last button on the last form. Know what that gets us? It gets us three months of wasted time, and our estimate will still be off. Possibly off by a factor of four. WTF, mate? No way we could be surprised by something! We uncovered every particle. We turned every stone. How is it we still came across unknowns? Because we STILL didn’t know what we didn’t know. How could we? We didn’t know to ask. The worst part is, we’ve now convinced the product that this is NOT an estimate. It is a solid number based on massive research and an endless number of questions that they answered. There is absolutely now way you don’t know everything there is to know about this project now. No way there is anything you haven’t uncovered. And their faith in that “Esti-Quote” goes through the roof. When the project goes over this time, they might even begin to question whether or not you know what you’re doing. Who could blame them? You drilled them for weeks about every little thing, and when they complained about all the questions, you told them you wanted to uncover everything so there would be no surprises. SO we set them up to faile Guess, Then Plan We had a chance. At the beginning we could have just said, “That’s just a gut-feeling estimate, based on my past experience with similar projects. There could still be surprises.” If we spend SOME time doing SOME discovery and then bounce that against our own past experiences, we can come up with a fairly healthy estimate. We can then help the product owner understand that an estimate is a guess. Sure, it’s an educated guess, but it is still a guess. If we get it right it will be almost completely luck. Then, we help them to plan the development by taking that guess (yes, they still need the guess for planning purposes) and start measuring early and often to see if we still think we are right. We should adjust the estimate and alert the product owner as soon as we see problems (bad news does not age well) and we should be able to see any problems immediately if we are constantly measuring our pace. In lean software, we start with that guess and begin measuring cycle times immediately. Then we can make projections based on those cycle times and compare them to our estimate. This constant feedback is the best way to ensure that there are no surprises at the END of the project. There sill still be surprises, but we’ll see them sooner and have a better understanding of how they will affect our overall timeline. What do you think?

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• Do I deserve a promotion/higher salary?

  - by anonCoder

  I'm a software developer and have been working at my current employer for almost 2 years. I joined straight out of university, so this is my first real full-time job. I was employed as a junior developer with no real responsibilities. In the last year, I have been given more responsiibility. I am the official contact person at my company for a number of clients. I have represented the company by myself in off-site meetings with clients. My software development role has grown. I now have specialised knowledge in certain tools/products/technologies that no one else here does. My problem is that I am still officially a junior developer, and still earning less than I feel I am worth. Am I being taken advantage of? How long should I reasonably expect to stay a junior developer before I expect a promotion of some kind? What would you do in my situation?

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• Android Swipe In Unity 3D World with AR

  - by Christian

  I am working on an AR application using Unity3D and the Vuforia SDK for Android. The way the application works is a when the designated image(a frame marker in our case) is recognized by the camera, a 3D island is rendered at that spot. Currently I am able to detect when/which objects are touched on the model by raycasting. I also am able to successfully detect a swipe using this code: if (Input.touchCount > 0) { Touch touch = Input.touches[0]; switch (touch.phase) { case TouchPhase.Began: couldBeSwipe = true; startPos = touch.position; startTime = Time.time; break; case TouchPhase.Moved: if (Mathf.Abs(touch.position.y - startPos.y) > comfortZoneY) { couldBeSwipe = false; } //track points here for raycast if it is swipe break; case TouchPhase.Stationary: couldBeSwipe = false; break; case TouchPhase.Ended: float swipeTime = Time.time - startTime; float swipeDist = (touch.position - startPos).magnitude; if (couldBeSwipe && (swipeTime < maxSwipeTime) && (swipeDist > minSwipeDist)) { // It's a swiiiiiiiiiiiipe! float swipeDirection = Mathf.Sign(touch.position.y - startPos.y); // Do something here in reaction to the swipe. swipeCounter.IncrementCounter(); } break; } touchInfo.SetTouchInfo (Time.time-startTime,(touch.position-startPos).magnitude,Mathf.Abs (touch.position.y-startPos.y)); } Thanks to andeeeee for the logic. But I want to have some interaction in the 3D world based on the swipe on the screen. I.E. If the user swipes over unoccluded enemies, they die. My first thought was to track all the points in the moved TouchPhase, and then if it is a swipe raycast into all those points and kill any enemy that is hit. Is there a better way to do this? What is the best approach? Thanks for the help!

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• DBA Best Practices - A Blog Series: Episode 1 - Backups

  - by Argenis

    This blog post is part of the DBA Best Practices series, on which various topics of concern for daily database operations are discussed. Your feedback and comments are very much welcome, so please drop by the comments section and be sure to leave your thoughts on the subject. Morning Coffee When I was a DBA, the first thing I did when I sat down at my desk at work was checking that all backups had completed successfully. It really was more of a ritual, since I had a dual system in place to check for backup completion: 1) the scheduled agent jobs to back up the databases were set to alert the NOC in failure, and 2) I had a script run from a central server every so often to check for any backup failures. Why the redundancy, you might ask. Well, for one I was once bitten by the fact that database mail doesn't work 100% of the time. Potential causes for failure include issues on the SMTP box that relays your server email, firewall problems, DNS issues, etc. And so to be sure that my backups completed fine, I needed to rely on a mechanism other than having the servers do the taking - I needed to interrogate the servers and ask each one if an issue had occurred. This is why I had a script run every so often. Some of you might have monitoring tools in place like Microsoft System Center Operations Manager (SCOM) or similar 3rd party products that would track all these things for you. But at that moment, we had no resort but to write our own Powershell scripts to do it. Now it goes without saying that if you don't have backups in place, you might as well find another career. Your most sacred job as a DBA is to protect the data from a disaster, and only properly safeguarded backups can offer you peace of mind here. "But, we have a cluster...we don't need backups" Sadly I've heard this line more than I would have liked to. You need to understand that a cluster is comprised of shared storage, and that is precisely your single point of failure. A cluster will protect you from an issue at the Operating System level, and also under an outage of any SQL-related service or dependent devices. But it will most definitely NOT protect you against corruption, nor will it protect you against somebody deleting data from a table - accidentally or otherwise. Backup, fine. How often do I take a backup? The answer to this is something you will hear frequently when working with databases: it depends. What does it depend on? For one, you need to understand how much data your business is willing to lose. This is what's called Recovery Point Objective, or RPO. If you don't know how much data your business is willing to lose, you need to have an honest and realistic conversation about data loss expectations with your customers, internal or external. From my experience, their first answer to the question "how much data loss can you withstand?" will be "zero". In that case, you will need to explain how zero data loss is very difficult and very costly to achieve, even in today's computing environments. Do you want to go ahead and take full backups of all your databases every hour, or even every day? Probably not, because of the impact that taking a full backup can have on a system. That's what differential and transaction log backups are for. Have I answered the question of how often to take a backup? No, and I did that on purpose. You need to think about how much time you have to recover from any event that requires you to restore your databases. This is what's called Recovery Time Objective. Again, if you go ask your customer how long of an outage they can withstand, at first you will get a completely unrealistic number - and that will be your starting point for discussing a solution that is cost effective. The point that I'm trying to get across is that you need to have a plan. This plan needs to be practiced, and tested. Like a football playbook, you need to rehearse the moves you'll perform when the time comes. How often is up to you, and the objective is that you feel better about yourself and the steps you need to follow when emergency strikes. A backup is nothing more than an untested restore Backups are files. Files are prone to corruption. Put those two together and realize how you feel about those backups sitting on that network drive. When was the last time you restored any of those? Restoring your backups on another box - that, by the way, doesn't have to match the specs of your production server - will give you two things: 1) peace of mind, because now you know that your backups are good and 2) a place to offload your consistency checks with DBCC CHECKDB or any of the other DBCC commands like CHECKTABLE or CHECKCATALOG. This is a great strategy for VLDBs that cannot withstand the additional load created by the consistency checks. If you choose to offload your consistency checks to another server though, be sure to run DBCC CHECKDB WITH PHYSICALONLY on the production server, and if you're using SQL Server 2008 R2 SP1 CU4 and above, be sure to enable traceflags 2562 and/or 2549, which will speed up the PHYSICALONLY checks further - you can read more about this enhancement here. Back to the "How Often" question for a second. If you have the disk, and the network latency, and the system resources to do so, why not backup the transaction log often? As in, every 5 minutes, or even less than that? There's not much downside to doing it, as you will have to clear the log with a backup sooner than later, lest you risk running out space on your tlog, or even your drive. The one drawback to this approach is that you will have more files to deal with at restore time, and processing each file will add a bit of extra time to the entire process. But it might be worth that time knowing that you minimized the amount of data lost. Again, test your plan to make sure that it matches your particular needs. Where to back up to? Network share? Locally? SAN volume? This is another topic where everybody has a favorite choice. So, I'll stick to mentioning what I like to do and what I consider to be the best practice in this regard. I like to backup to a SAN volume, i.e., a drive that actually lives in the SAN, and can be easily attached to another server in a pinch, saving you valuable time - you wouldn't need to restore files on the network (slow) or pull out drives out a dead server (been there, done that, it’s also slow!). The key is to have a copy of those backup files made quickly, and, if at all possible, to a remote target on a different datacenter - or even the cloud. There are plenty of solutions out there that can help you put such a solution together. That right there is the first step towards a practical Disaster Recovery plan. But there's much more to DR, and that's material for a different blog post in this series.

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• Google Wave Extensions Gallery Launches

  Developers can now post their tools and add-ons for the real-time communications app.

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• Why do apt-get and wget fail on my server when ping is working?

  - by klox

  Yesterday my server still OK, but today after try to sudo apt-get update i got this error: update process. I try: sudo rm /var/lib/apt/lists/* -vf And got This.Then try update again, but it's not solving my problem then show May be still same error. I checked my internet connection try ping google.com, get result : PING google.com (74.125.235.40) 56(84) bytes of data. From 136.198.117.254: icmp_seq=1 Redirect Network(New nexthop: fw1.jvc-jein.co.id (136.198.117.6)) 64 bytes from sin01s05-in-f8.1e100.net (74.125.235.40): icmp_req=1 ttl=53 time=20.6 ms 64 bytes from sin01s05-in-f8.1e100.net (74.125.235.40): icmp_req=2 ttl=53 time=18.2 ms 64 bytes from sin01s05-in-f8.1e100.net (74.125.235.40): icmp_req=3 ttl=53 time=33.0 ms 64 bytes from sin01s05-in-f8.1e100.net (74.125.235.40): icmp_req=4 ttl=53 time=30.0 ms 64 bytes from sin01s05-in-f8.1e100.net (74.125.235.40): icmp_req=5 ttl=53 time=28.1 ms In some sites said that may be it caused by getdeb server is down. try to install: jeinqa@SVRQAR:~$ sudo apt-get install pastebinit Reading package lists... Error! E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_precise-security_restricted_binary-amd64_Packages E: The package lists or status file could not be parsed or opened. try : sudo ufw status verbose result : Status: inactive

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• Extending SSIS with custom Data Flow components (Presentation)

  Download the slides and sample code from my Extending SSIS with custom Data Flow components presentation, first presented at the SQLBits II (The SQL) Community Conference. Abstract Get some real-world insights into developing data flow components for SSIS. This starts with an introduction to the data flow pipeline engine, and explains the real differences between adapters and the three sub-types of transformation. Understanding how the different types of component behave and manage data is key to writing components of your own, and probably should but be required knowledge for anyone building packages at all. Using sample code throughout, I will show you how to write components, as well as highlighting best practice and lessons learned. The sample code includes fully working example projects for source, destination and transformation components. Presentation & Samples (358KB) Extending SSIS with custom Data Flow components.zip

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