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• A space-efficient guest filesystem for grow-as-needed virtual disks ?

  - by Steve Schnepp

  A common practice is to use non-preallocated virtual disks. Since they only grow as needed, it makes them perfect for fast backup, overallocation and creation speed. Since file systems are usually based on physical disks they have the tendency to use the whole area available1 in order to increase the speed2 or reliability3. I'm searching a filesystem that does the exact opposite : try to touch the minimum blocks need by an aggressive block reuse. I would happily trade some performance for space usage. There is already a similar question, but it is rather general. I have very specific goal : space-efficiency. 1. Like page caching uses all the free physical memory 2. Canonical example : online defragmentation 3. Canonical example : snapshotting

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• Optimal way to make MySQL backups for fairly large databases (MyISAM / InnoDB)

  - by WinkyWolly

  Currently we have one beefy MySQL database that runs a couple of high traffic Django based websites as well as some e-commerce websites of decent size. As a result we have a fair amount of large databases using both InnoDB and MyISAM tables. Unfortunately we've recently hit a wall due to the amount of traffic so I've setup another master server to help alleviate reads / backups. Now at the moment I simply use mysqldump with a few arguments and it's proven to be fine.. until now. Obviously mysqldump is a slow quick method however I believe we've outgrown its use. I now need a good alternative and have been looking into utilizing Maatkits mk-parallel-dump utility or an LVM snapshot solution. Succinct short version: I have a fairly large MySQL databases I need to backup Current method using mysqldump is inefficient and slow (causing issues) Looking into something such as mk-parallel-dump or LVM snapshots Any recommendations or ideas would be appreciated - since I have to re-do how we're doing things I rather have it done properly / most efficient :).

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• eSTEP Newsletter for the technical EMEA partner community

  - by mseika

  We are pleased to present to you the first issue of the eSTEP Newsletter, which is dedicated to support the technical EMEA partner community in the effort to provide more information on what is going on within the corporation, what is the technical news regarding Hardware, events and all the important things which we think may be of interest to you. Invitation: STEP TechCast: Oracle Solaris 11 Express Get an insight on how Oracle Solaris 11 Express has raised the bar on the innovation introduced in Oracle Solaris 10. Learn about the new integrated features such as: network based package management tools improvements to built-in virtualization new virtualised network architecture security enhancements file system evolution  Learn how Oracle Solaris 11 Express provides greatly decreased planned system downtime, performs a completely safe system upgrade, achieves an unprecedented level of flexibility for application consolidation, and provides the highest levels of security in your datacenter. Date and time: Thursday, 7. July 2011, 13:00 - 14:00 CEST Speaker: Joost Pronk van Hoogeveen Target audience: Tech Presales Webcast Coordinates: You will find the coordinates in the eSTEP portal under the Events tab. Use your email-adress and PIN: eSTEP_2011 to get access. We are happy to get your comments and feedback.

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• Where should "display functions" live in an MVC web app?

  - by User

  I'm using the Yii Framework which is an MVC php framework that is pretty similar to your standard web-based MVC framework. I want to display the related data from a many-to-many table as a list of strings in my view. Assuming a table schema like: tag { id, name } post { id, title, content, date } post_tag { post_id, tag_id } A post will display like: Date: 9/27/2012 Title: Some Title Content: blah blah blah... Tags: Smart Funny Cool Informative I can achieve this by doing something like this in my Post view: <?php echo join(' ', array_map(function($tag) { return $tag->name; }, $model->tags)); ?> (where $model->tags is an array of Tag objects associated with my model) My questions are: Is this amount of code/logic okay in the view? (Personally I think I'd rather just reference a property or call a single function.) If not, where should this code live? In the model? the controller? a helper? Potentially I may want to use in in other views as well. Ultimately I think its purely a display issue which would make me think it should be in the view, but then I have to repeat the code in any view I want to use it in.

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• Nginx proxy to Apache - resolve HTTP ORIGIN

  - by Fratyr

  I have a server setup with nginx serving static content and proxy all PHP/dynamic requests to apache on 127.0.0.1 I'm building an API for my databases, and I need to allow clients by their origin (domain name), rather than just IP. Based on CORS rules. So when I send an HTTP header header("Access-Control-Allow-Origin: www.client-requesting.myapi.com"); from my API server, I have to tell it which origin I allow, otherwise client side requests won't work to my API due to same-origin policy. The question is how can I know which domain name (if any) called my API? What should be the nginx and apache configuration to pass the origin parameter? I tried to google, and all I found is some possible solution with mod_rpaf, but I wanted to be sure. Thanks!

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• Almost working 2D Collisions

  - by TheGag96

  I'm terribly sorry I'm asking this question YET AGAIN, but I can almost guarantee that this will be the last time I'll have to ask. I'm currently on the verge of FINALLY getting these collisions to work for my game, made with libGDX in Java. My collisions use the same method as (and are basically copied and modified code from) the XNA Platformer example (here) where the direction of the collision is based on the rectangle where two objects are overlapping. The collisions themselves almost work perfectly, but for some reason, holding down/up and left and colliding with the floor/ceiling while doing so doesn't seem to work well. I'm not at all sure why. Instead of vaguely giving my problem and snippets of code, I've decided to instead provide a binary and the source of the game I have so far so you can see for yourself what my problem is. Link. (Note: make sure you unzip everything into a folder somewhere or it will not work) You'll find the collision code in the method workingCollisions() in Link.java. Please excuse the messy code and terrible graphics as this whole thing is in pre-pre-alpha. If anyone is kind enough and helps me out here, you are the best person ever. I'm completely desperate; I've been trying this on and off for months and I just can't get it to work. I cannot thank you enough.

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• Differences between Cherry mechanical keyboard switches?

  - by TreyK

  I want a comfortable, responsive mechanical switch keyboard. My only concern about mechanical switch keyboards is the noise. Boards based off of the Cherry MX Blue seem to be the loudest, but apparently offer increased tactility. I don't mind a clicky noise (I would actually prefer a bit of noise), I just don't want anything overpowering. What are the different types of Cherry mechanical switches are out there, and what separates one from the other? Also, where would I be able to test one out?

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• Architecture of a "website generator" web application

  - by Resorath

  What is the most maintainable and efficient way to architect a web application who's purpose is to host and generate websites which can be customized to a certain degree? There are a lot of these style of applications in the wild that generate all kinds of sites, from sites that host World of Warcraft guilds like guildlaunch to other sites like my wedding for wedding site hosting. My question is, what is the basic architecture that these sites operate on? I imagine there are two ways of thinking about this. A central set of code that all sites on the host run against, and it acts differently based on which site was visited. In this manner, when the base code is updated all sites are updated simultaneously. Or, the code for an individual site exists in a silo, and is simply replicated to a new directory each time a site is created. When an update needs to be applied, the code is pushed out to each site silo. In my case, I am working in PHP with the CodeIgniter framework, however the answer need not be limited to this case. Which method (if any) creates a more maintainable and efficient architecture to manage this style of web application?

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• TechEd 2012: Windows Phone Exam Cram

  - by Tim Murphy

  Usually speakers take offence if you wear headphones in their talk.  For the exam cram session it was a requirement.  This was because it was a cubical walled room with an open top next to a study hall. While no-one was going to come out of this session ready to take a test, I am glad that I took the time to attend it.  There was a fair amount of material that you should know already if you have ever taken a certification test before.  This was packed around a mix of key concepts and some tidbits that marked where some of the pitfalls are for this particular test.  The biggest warning was that the test is based on Windows Phone 7.0 and not Mango meaning that you have to be careful that you don’t answer a question in the wrong context. I would suggest if you have a chance to take attend a free session grab it.  It is a good break from the other hard core talks and will get your mind into a mode for getting your next certification.  Good luck. del.icio.us Tags: TechEd,TechEd 2012,Windows Phone,Exam Cram,Certification

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• "Can't open display" even after access with xhost

  - by Yann

  I'm trying to run a graphical program remotely, without using ssh. I've set the display variable on the server (let's say server.com, Linux, not ubuntu, and no su rights) to point to my workstation (workstation.com, ubuntu 10.04) setenv DISPLAY workstation.com:0 Then on my workstation I've tried both xhost +server.com and xhost + Then I ssh into the server (to test things): ssh [email protected] and try to run xclock, and get the following error: Error: Can't open display: workstation.com:0 I've looked at /etc/ssh/ssh_config on the workstation and I should be forwarding correctly: X11Forwarding yes. How do I go about troubleshooting this? What logs on the workstation document these failed attempts? To explain why I'm doing this: I want to run a batch job on a server to debug an MPI-based parallel program. I want to run xterm as the batch job executable, per the instructions provided by the system admins. This setup use to work. I reinstalled things on my workstation and since then I frequently get one-time message along the lines The authenticity of host 'hostname (XXX.XXX.XXX.XX)' can't be established. My attempt to fix the above was to move my ~/.ssh/known_hosts file to a back up on both server and host, and then to ssh from each to the other with the flag -o StrictHostKeyChecking=no. I no longer get that message, but I was wondering does this play a part in why X11 forwarding is not working?

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• How can I read a portion of one Minecraft world file and write it into another?

  - by RapierMother

  I'm looking to read block data from one Minecraft world and write the data into certain places in another. I have a Minecraft world, let's say "TemplateWorld", and a 2D list of Point objects. I'm developing an application that should use the x and y values of these Points as x and z reference coordinates from which to read constant-sized areas of blocks from the TemplateWorld. It should then write these blocks into another Minecraft world at constant y coordinates, with x & z coordinates determined based on each Point's index in the 2D list. The issue is that, while I've found a decent amount of information online regarding Minecraft world formats, I haven't found what I really need: more of a breakdown by hex address of where/what everything is. For example, I could have the TemplateWorld actually be a .schematic file rather than a world; I just need to be able to read the bytes of the file, know that the actual block data starts always at a certain address (or after a certain instance of FF, etc.), and how it's stored. Once I know that, it's easy as pie to just read the bytes and store them.

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• Question regarding Readability vs Processing Time

  - by Jordy

  I am creating a flowchart for a program with multiple sequential steps. Every step should be performed if the previous step is succesful. I use a c-based programming language so the lay-out would be something like this: METHOD 1: if(step_one_succeeded()) { if(step_two_succeeded()) { if(step_three_succeeded()) { //etc. etc. } } } If my program would have 15+ steps, the resulting code would be terribly unfriendly to read. So I changed my design and implemented a global errorcode that I keep passing by reference, make everything more readable. The resulting code would be something like this: METHOD 2: int _no_error = 0; step_one(_no_error); if(_no_error == 0) step_two(_no_error); if(_no_error == 0) step_three(_no_error); if(_no_error == 0) step_two(_no_error); The cyclomatic complexibility stays the same. Now let's say there are N number of steps. And let's assume that checking a condition is 1 clock long and performing a step doesn't take up time. The processing speed of Method1 can be anywhere between 1 and N. The processing speed of Method2 however is always equal to N-1. So Method1 will be faster most of the time. Which brings me to my question, is it bad practice to sacrifice time in order to make the code more readable? And why (not)?

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• Hosting and scaling a Facebook application in the cloud? [migrated]

  - by DhruvPathak

  We would be building a Facebook application in Django (Python), but still not sure of where to host it economically, and with a good provision to scale in case the app gets viral. Some details about the app: Would be HTML based like a website,using django as a framework. 100K is the number of expected pageviews in a day, if the app is viral. The users will not generate any media content, only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on Google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment, cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. (Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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• Challenge Ends on Friday!

  - by Yolande Poirier

  This is your last chance to win a JavaOne trip. Submit a project video and code for the IoT Developer Challenge by this Friday, May 30.  12 JavaOne trips will be awarded to 3 professional teams and one student team. Members of two student teams will win laptops and certification training vouchers. Ask your last minute questions on the coaching form or the Challenge forum. They will be answered promptly. Your project video should explain how your project works. Any common video format such as mp4, avi, mov is fine. Your project must use Java Embedded - whether it is Java SE Embedded or ME Embedded - with the hardware of your choice, including any devices, boards and IoT technology. The project will be judged based on the project implementation, innovation and business usefulness. More details on the IoT Developer Challenge website  Just for fun! Here is a video of Vinicius Senger giving a tour of his home lab, and showing his boards and gadgets. &lt;span id=&quot;XinhaEditingPostion&quot;&gt;&lt;/span&gt;

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• Tools to manage large network of heterogeneous web applications?

  - by Andrew

  I recently started a new job where I've been tasked with managing a global network of heterogenous web applications. There's very little documentation. My first order of business is to create an inventory of all of the web applications. Are there any tools out there to manage a large group of web apps? I'd like to collect a large dataset for each website including: logins for web based control panels logins to FTP/ssh accounts Google analytics tracking code for each site 3rd party libraries used SSL certs, issuers, and expiration dates etc I know I could keep the information in Excel or build a custom database, but I'm hoping there's already a tool out there to help me with this.

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• china and gmail attachs -

  - by doug

  "We have evidence to suggest that a primary goal of the attackers was accessing the Gmail accounts of Chinese human rights activists. Based on our investigation to date we believe their attack did not achieve that objective. Only two Gmail accounts appear to have been accessed, and that activity was limited to account information (such as the date the account was created) and subject line, rather than the content of emails themselves.” [source] I don't know much about how internet works, but as long the chines gov has access to the chines internet providers servers, why do they need to hack gmail accounts? I assume that i don't understand how submitting/writing a message(from user to gmail servers) works, in order to be sent later to the other email address. Who can tell me how submitting a message to a web form works?

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• Dealing with Fine-Grained Cache Entries in Coherence

  - by jpurdy

  On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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• How do I associate server traffic to a domain hosted on that server?

  - by morley

  I have three or four Linux servers, each of which hosts anywhere from 5 to 50 domains. Each domain has its own folder: /www/projectname/web/ Logs go in: /www/projectname/log However, if there's a traffic spike (or, as I see it on my end, a memory usage spike), I'm not sure how to figure out which domain is responsible for the traffic without running tail -f on each of the projects and making an educated guess based on how fast things scroll. There's got to be a better way! There probably is, but I haven't seen it. And the last time I checked, bandwidth monitors only report system-wide load. So if anyone knows how to do this the right way, please let me know. Thanks!

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• How should I create a mutable, varied jtree with arbitrary/generic category nodes?

  - by Pureferret

  Please note: I don't want coding help here, I'm on Programmers for a reason. I want to improve my program planning/writing skills not (just) my understanding of Java. I'm trying to figure out how to make a tree which has an arbitrary category system, based on the skills listed for this LARP game here. My previous attempt had a bool for whether a skill was also a category. Trying to code around that was messy. Drawing out my tree I noticed that only my 'leaves' were skills and I'd labeled the others as categories. Explanation of tree: The Tree is 'born' with a set of hard coded highest level categories (Weapons, Physical and Mental, Medical etc.). Fro mthis the user needs to be able to add a skill. Ultimately they want to add 'One-handed Sword Specialisation' for instance. To do so you'd ideally click 'add' with Weapons selected and then select One-handed from a combobox, then click add again and enter a name in a text field. Then click add again to add a 'level' or 'tier' first proficiency, then specialisation. Of course if you want to buy a different skill it's completely different, which is what I'm having trouble getting my head around let alone programming in. What is a good system for describing this sort of tree in code? All the other JTree examples I've seen have some predictable pattern, and I don't want to have to code this all in 'literals'. Should I be using abstract classes? Interfaces? How can I make this sort of cluster of objects extensible when I add in other skills not listed above that behave differently? If there is not a good system to use, if there a good process for working out how to do this sort of thing?

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• What are some ways to separate game logic from animations and the draw loop?

  - by TMV

  I have only previously made flash games, using MovieClips and such to separate out my animations from my game logic. Now I am getting into trying my hand at making a game for Android, but the game programming theory around separating these things still confuses me. I come from a background of developing non game web applications so I am versed in more MVC like patterns and am stuck in that mindset as I approach game programming. I want to do things like abstract my game by having, for example, a game board class that contains the data for a grid of tiles with instances of a tile class that each contain properties. I can give my draw loop access to this and have it draw the game board based on the properties of each tile on the game board, but I don't understand where exactly animation should go. As far as I can tell, animation sort of sits between the abstracted game logic (model) and the draw loop (view). With my MVC mindset, it's frustrating trying to decide where animation is actually supposed to go. It would have quite a bit of data associated with it like a model, but seemingly needs to be very closely coupled with the draw loop in order to have things like frame independent animation. How can I break out of this mindset and start thinking about patterns that make more sense for games?

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• That Tool is cURLy

  When you just use IE, Firefox or Chrome it can be easy to forget that HTTP is about more then just going to check the latest tech news at Engadget. It is a full and rich protocol, and a great way to experience that richness is the powerful command line utility cURL. cURL has a lot of options, but the syntax starts out simple. You can retrieve the contents of a web page with a simple curl http://blogs.claritycon.com/. The results should be the full text of the web page, tags and all. From there, you can use X to specify the HTTP verb to use, POST, PUT, DELETE, PATCH, etc and d to specify the payload of a POST or PUT. I have found cURL to be incredibly useful for two scenarios. First, as a good way to test basic web services. Second, while working a bit with CouchDB and another document based database, cURL has helped me learn more about RESTful APIs, including different verbs and response codes. cURL is a mainstay in our environments and programming languages precisely because it is simple, powerful and discoverable. I encourage more .NET developers to take a look, bask on the command line for a while and enjoy the plain text of the web. And this excellent logo:     -- Relevant Links -- Its not always the case with manuals, but the manual for cURL is quite useful: http://curl.haxx.se/docs/manual.html To make your command line look a little nicer (and more powerful) on Windows, check out Console and add some transparency effects: http://sourceforge.net/projects/console/Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• game play strategy in an arena

  - by joulesm

  I am writing a player's behavior for an arena game, and I'm wondering if you can offer some strategies. I'm writing it in Python, but I'm just interested in the high level game play. Here are the game aspects: Arena is a circle of a given size. The arena size shrinks every round to help break ties. Players are much smaller circles, can be on teams of 1 or 2 players. Players attack by colliding with other players, and based on the physics of the collision (speed of both players, angle), one could force another player out of the arena. Once a player is out of the arena, they are out of the game (for that round). The goal is to be the only team with players left in the arena. All other players have been pushed (through collisions or mistakes) out of the arena. It is possible for there to be no winner if the last two players exit the arena at the same time. Once the player has been programmed, the game just runs. There is no human intervention in the game. I'm thinking it's easiest to implement a few simple programmatic rules for my player to follow. For example, stay close to center of the arena, attack opponents from the inner side of the arena, etc. Are there any good simple game strategies? Would adding a random aspect to the game help? For example, to avoid predictability by the other team or something. Thanks in advance.

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• Are there other application layer firewalls like Microfot TMG (ISA) that do advanced http rules?

  - by Bret Fisher

  Since the old days ISA and now TMG have had several great features that I often want to deploy to my customers because of the enhanced functionality and security, but often the cost of an additinal server HW, Windows Server, and TMG license is too much to justify when compaired to a $300-500 appliance. Are there other gateway firewalls that can perform one or more of these application layer features: pre-auth incoming http traffic against AD/LDAP before sending packets to internal server (forms auth or basic creds popup)? read host headers of incoming http traffic (even on https) to a single public IP and route packets to different internal servers based on that host header?

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• What will be the better way for data retrieval on application that needs to handle limited amount of data?

  - by Milanix

  Just moved this question from Stack Overflow. Since, adding my code snippets itself would make this question really long. Instead, I am pretty interested in knowing a better ways for data retrieval on application that needs to handle limited amount of data which isn't updated regularly. Let's take this example: I am writing an application which gets a schedule as an XML from server. I have written a logic in order to parse XML version and update database only if the version is newer than the local version. Although the update is checked automatically/manually on daily basis based on user preference, the actual version update happens only once per few months or so. Since, this is done by some other authority which doesn't provide API but, rather inform publicly on their changes. The actual XML contains a "(n number of groups)(days in a week) (n number of schedule)" . The group is usually 6 and the number of schedule is usually 2. So basically there would usually be only around 100 strings. Now although I have used SQLite at the moment. I want to know how to make update on database. Should I show progress dialog that the application is updating and exit the app when it's done? Since, my updates are infrequent i don't think this will really harm user experience but, is there any better ways to do it? Because I don't want update to be made when user is searching which is done using database. This will cause an database already open exception. At least I have faced this problem before. Is it better to rather parse XML every time when user wants to view certain things or to use SQLite? Since, I make lots of use of adapter in my app to create lists, will that degrade the performance?

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• How to get started in the development industry? [closed]

  - by Peter Fren

  My life is coding. I was born in 1982 and my first computer was an amiga. I started learning Amiga BASIC. To cut a long story short, I know many things about several programming languages. Being unemployed(I achieved the german abitur, should be similar to a high school degree and I studied a few semesters of mechanical engineering in 2002(I learned JAVA back then)) I have no idea how to use this ability. I have never done commissional work, every task I solved was based on my own wishes and desires. I do not know how to write a FSD or PRD or put it into code. So the question is, why should anyone hire me? I specialized in kinect development but all jobs I applied for on odesk and similar were awarded to others without me knowing why. I don't know what I should do with my skills professionally. What do you suggest? As this board has weird rules, tell me where to find answers if this is the wrong place.

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