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  • Explain Model View Controller

    - by Channel72
    My experience with developing dynamic websites is limited mostly to Java servlets. I've used Tomcat to develop various Java servlets, and I wouldn't hesitate to say that I'm reasonably proficient with this technology, as well as with client-side HTML/CSS/Javascript for the front-end. When I think "dynamic website", I think: user requests a URL with a query string, server receives the query, and then proceeds to output HTML dynamically in order to respond to the query. This often involves communication with a database in order to fetch requested data for display. This is basically the idea behind the doGet method of a Java HttpServlet. But these days, I'm hearing more and more about newer frameworks such as Django and Ruby on Rails, all of which take advantage of the "Model View Controller" architecture. I've read various articles which explain MVC, but I'm having trouble really understanding the benefits. I understand that the general idea is to separate business logic from UI logic, but I fail to see how this is anything really different from normal web programming. Web programming, by it's very nature, forces you to separate business logic (back-end server-side programming) from UI programming (client-side HTML or Javascript), because the two exist in entirely different spheres of programming. Question: What does MVC offer over something like a Java servlet, and more importantly, what exactly is MVC and how is it different from what you would normally do to develop a dynamic website using a more traditional approach such as a Java servlet (or even something older like CGI). If possible, when explaining MVC, please provide an example which illustrates how MVC is applied to the web development process, and how it is beneficial.

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  • Logical and Physical Modeling for Analytical Applications

    - by Dejan Sarka
    I am proud to announce that my first course for Pluralsight is released. The course title is Logical and Physical Modeling for Analytical Applications. Here is the description of the course. A bad data model leads to an application that does not perform well. Therefore, when developing an application, you should create a good data model from the start. However, even the best logical model can’t help when the physical implementation is bad. It is also important to know how SQL Server stores and accesses data, and how to optimize the data access. Database optimization starts by splitting transactional and analytical applications. In this course, you learn how to support analytical applications with logical design, get understanding of the problems with data access for queries that deal with large amounts of data, and learn about SQL Server optimizations that help solving these problems. Enjoy the course!

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  • C#.NET (AForge) against Java (JavaCV, JMF) for video processing

    - by Leron
    I'm starting to get really confused looking deeper and deeper at video processing world and searching for optimal choices. This is the reason to post this and some other questions to try and navigate myself in the best possible way. I really like Java, working with Java, coding with Java, at the same time C# is not that different from Java and Visual Studio is maybe the best IDE I've been working with. So even though I really want to do my projects in Java so I can get better and better Java programmer at the same time I'm really attract to video processing and even though I'm still at the beginning of this journey I want to take the right path. So I'm really in doubt could Java be used in a production environment for serious video processing software. As the title says I already have been looking at maybe the two most used technologies for video processing in Java - JMF and JavaCV and I'm starting to think that even they are used and they provide some functionality, when it comes to real work and real project that's not the first thing that comes to once mind, I mean to someone that have a professional opinion about this. On the other hand I haven't got the time to investigate .NET (c# specificly) options but even AForge looks a lot more serious library then those provided for Java. So in general -either ways I'm gonna spend a lot of time learning some technology and trying to do something that make sense with it, but my plan is at the end the thing that I'll eventually come up to be my headline project. To represent my skills and eventually help me find a job in the field. So I really don't want to spend time learning something that will give me the programming result I want but at the same time is not something that is needed in the real world development. So what is your opinion, which language, technology is better for this specific issue. Which one worths more in terms that I specified above?

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  • Java Road Trip: Code to Coast (#javaroadtrip)

    - by Justin Kestelyn
    Hey, have you heard? The Java Road Trip bus may be stopping at a city near you this summer, starting June 14. And your peeps at Oracle Technology Network have donated some goodies. What is the Java Road Trip? Basically, we have packed a rock-star bus with demos (Java FX, Oracle ADF, Java EE 6, JDK 7, GlassFish, Java ME) and are putting it on the road; it will make 20 stops across the U.S. in the next couple of months (and MAY may make a special appearance at JavaOne, if we can find a big enough parking space). In many cases these stops will coincide with Java or Oracle user group meet-ups and will always involve beer, food, and free stuff. Furthermore, engineers from HQ will be flying out at various times to rendezvous with these meet-ups and answer your questions. Also, because this tour will only reach a relatively small number of people, we're working hard to provide a virtual experience: there will be a blogger/videographer/photog/tweeter on board, reporting on its every move. You'll find all this content at java.com/roadtrip, and you can get real-time updates via @java. And this new update: If you're attending ODTUG Kaleidoscope in Washington, D.C., in late June, you'll get a chance to see the Java Bus in all its glory. And don't forget your t-shirt, cup, and screen cleaner, all provided by Oracle Technology Network.

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  • Java.net Reborn

    - by Bob Rhubart
    Java.net, the home of  Java community projects, has been re-launched with a new look and new tools for developers.  The move from CollabNet to the Kenai infrastructure offers more flexibility for developers who want to host or contribute to community projects.  Instead of the large, fixed infrastructure per project (for example, several mailing lists per project), Kenai's ala carte features allow users to take only what they need. "We will continue to have the great mix of blogs, forums, and editorial content as well as new tools on the project side, including Mercurial, Git, and JIRA for developers," Java.net Community Manager Sonya Barry explains.  The migration was huge effort. Over 1400 projects were migrated (and some 30 projects are left to go). A large part of the migration was a big cleanup of abandoned projects. With the high abandonment rate of open source projects, the was a lot to remove. The new java.net site is smaller, faster and now the percentage of good, current content is much higher. Check it out at http://home.java.net/   Technorati Tags: java,java.net,oracle,oracle technology network del.icio.us Tags: java,java.net,oracle,oracle technology network

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  • How You Helped Shape Java EE 7...

    - by reza_rahman
    I have been working with the JCP in various roles since EJB 3/Java EE 5 (much of it on my own time), eventually culminating in my decision to accept my current role at Oracle (despite it's inevitable set of unique challenges, a role I find by and large positive and fulfilling). During these years, it has always been clear to me that pretty much everyone in the JCP genuinely cares about openness, feedback and developer participation. Perhaps the most visible sign to date of this high regard for grassroots level input is a survey on Java EE 7 gathered a few months ago. The survey was designed to get open feedback on a number of critical issues central to the Java EE 7 umbrella specification including what APIs to include in the standard. When we started the survey, I don't think anyone was certain what the level of participation from developers would really be. I also think everyone was pleasantly surprised that a large number of developers (around 1100) took the time out to vote on these very important issues that could impact their own professional life. And it wasn't just a matter of the quantity of responses. I was particularly impressed with the quality of the comments made through the survey (some of which I'll try to do justice to below). With Java EE 7 under our belt and the horizons for Java EE 8 emerging, this is a good time to thank everyone that took the survey once again for their thoughts and let you know what the impact of your voice actually was. As an aside, you may be happy to know that we are working hard behind the scenes to try to put together a similar survey to help kick off the agenda for Java EE 8 (although this is by no means certain). I'll break things down by the questions asked in the survey, the responses and the resulting change in the specification. APIs to Add to Java EE 7 Full/Web Profile The first question in the survey asked which of four new candidate APIs (WebSocket, JSON-P, JBatch and JCache) should be added to the Java EE 7 Full and Web profile respectively. Developers by and large wanted all the new APIs added to the full platform. The comments expressed particularly strong support for WebSocket and JCache. Others expressed dissatisfaction over the lack of a JSON binding (as opposed to JSON processing) API. WebSocket, JSON-P and JBatch are now part of Java EE 7. In addition, the long-awaited Java EE Concurrency Utilities API was also included in the Full Profile. Unfortunately, JCache was not finalized in time for Java EE 7 and the decision was made not to hold up the Java EE release any longer. JCache continues to move forward strongly and will very likely be included in Java EE 8 (it will be available much sooner than Java EE 8 to boot). An emergent standard for JSON-B is also a strong possibility for Java EE 8. When it came to the Web Profile, developers were supportive of adding WebSocket and JSON-P, but not JBatch and JCache. Both WebSocket and JSON-P are now part of the Web Profile, now also including the already popular JAX-RS API. Enabling CDI by Default The second question asked whether CDI should be enabled in Java EE by default. The overwhelming majority of developers supported the default enablement of CDI. In addition, developers expressed a desire for better CDI/Java EE alignment (with regards to EJB and JSF in particular). Some developers expressed legitimate concerns over the performance implications of enabling CDI globally as well as the potential conflict with other JSR 330 implementations like Spring and Guice. CDI is enabled by default in Java EE 7. Respecting the legitimate concerns, CDI 1.1 was very careful to add additional controls around component scanning. While a lot of work was done in Java EE 6 and Java EE 7 around CDI alignment, further alignment is under serious consideration for Java EE 8. Consistent Usage of @Inject The third question was around using CDI/JSR 330 @Inject consistently vs. allowing JSRs to create their own injection annotations (e.g. @BatchContext). A majority of developers wanted consistent usage of @Inject. The comments again reflected a strong desire for CDI/Java EE alignment. A lot of emphasis in Java EE 7 was put into using @Inject consistently. For example, the JBatch specification is focused on using @Inject wherever possible. JAX-RS remains an exception with it's existing custom injection annotations. However, the JAX-RS specification leads understand the importance of eventual convergence, hopefully in Java EE 8. Expanding the Use of @Stereotype The fourth question was about expanding CDI @Stereotype to cover annotations across Java EE beyond just CDI. A solid majority of developers supported the idea of making @Stereotype more universal in Java EE. The comments maintained the general theme of strong support for CDI/Java EE alignment Unfortunately, there was not enough time and resources in Java EE 7 to implement this fairly pervasive feature. However, it remains a serious consideration for Java EE 8. Expanding Interceptor Use The final set of questions was about expanding interceptors further across Java EE. Developers strongly supported the concept. Along with injection, interceptors are now supported across all Java EE 7 components including Servlets, Filters, Listeners, JAX-WS endpoints, JAX-RS resources, WebSocket endpoints and so on. I hope you are encouraged by how your input to the survey helped shape Java EE 7 and continues to shape Java EE 8. Participating in these sorts of surveys is of course just one way of contributing to Java EE. Another great way to stay involved is the Adopt-A-JSR Program. A large number of developers are already participating through their local JUGs. You could of course become a Java EE JSR expert group member or observer. You should stay tuned to The Aquarium for the progress of Java EE 8 JSRs if that's something you want to look into...

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  • Java and .NET cost of use [on hold]

    - by 1110
    I work with .NET technology stack for about 4 years. I am learning and enjoy working with ASP MVC framework and I never did anything serious in other languages. This is not the question like what is better (I read all similar questions). What interest me is the cost of switching. For example: If you are about to start a start-up company today and you are in my situation not too much money, some good idea that you think others will use and have a knowledge of .NET. In my head I have a few questions that I can't answer and I know that somebody with experience can: 1) Java & .NET hosting. Suppose shared hosting is not good enough anymore, your site has grown and you need more resources. How much Java services is cheaper compared to .NET? 2) I didn't follow hype about ORACLE will kill java long time. Does oracle show interest in investing in java. I mean is is safe to bet on java as a technology when starting start-up (basically did oracle show some will to destroy java platform)? 3) I am not sure what I am asking here. When you use Java you can use JEEE stack or Java with third party stack (spring, hibernate, maven etc.). I saw a lot of project that work with second option if web application is not enterprise level but social networking site for example which stack is best pick? Summary of this question is is it safe to jump in to Java learn it and build product based on it. It's not too hard for me to learn it. But how much can I get from it.

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  • DexFile.class error in eclipse

    - by ninjasense
    I get this weird error everytime I debug in eclipse. It just seemed to appear one day and I was wondering if anyone else was running int the same problem. It does not affect my app in anyway visibly and does not cause a crash but it is an annoyance while debugging. Here is the full error: // Compiled from DexFile.java (version 1.5 : 49.0, super bit) public final class dalvik.system.DexFile { // Method descriptor #8 (Ljava/io/File;)V // Stack: 3, Locals: 2 public DexFile(java.io.File file) throws java.io.IOException; 0 aload_0 [this] 1 invokespecial java.lang.Object() [1] 4 new java.lang.RuntimeException [2] 7 dup 8 ldc <String "Stub!"> [3] 10 invokespecial java.lang.RuntimeException(java.lang.String) [4] 13 athrow Line numbers: [pc: 0, line: 4] Local variable table: [pc: 0, pc: 14] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 14] local: file index: 1 type: java.io.File // Method descriptor #18 (Ljava/lang/String;)V // Stack: 3, Locals: 2 public DexFile(java.lang.String fileName) throws java.io.IOException; 0 aload_0 [this] 1 invokespecial java.lang.Object() [1] 4 new java.lang.RuntimeException [2] 7 dup 8 ldc <String "Stub!"> [3] 10 invokespecial java.lang.RuntimeException(java.lang.String) [4] 13 athrow Line numbers: [pc: 0, line: 5] Local variable table: [pc: 0, pc: 14] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 14] local: fileName index: 1 type: java.lang.String // Method descriptor #22 (Ljava/lang/String;Ljava/lang/String;I)Ldalvik/system/DexFile; // Stack: 3, Locals: 3 public static dalvik.system.DexFile loadDex(java.lang.String sourcePathName, java.lang.String outputPathName, int flags) throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 6] Local variable table: [pc: 0, pc: 10] local: sourcePathName index: 0 type: java.lang.String [pc: 0, pc: 10] local: outputPathName index: 1 type: java.lang.String [pc: 0, pc: 10] local: flags index: 2 type: int // Method descriptor #28 ()Ljava/lang/String; // Stack: 3, Locals: 1 public java.lang.String getName(); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 7] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #30 ()V // Stack: 3, Locals: 1 public void close() throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 8] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #32 (Ljava/lang/String;Ljava/lang/ClassLoader;)Ljava/lang/Class; // Stack: 3, Locals: 3 public java.lang.Class loadClass(java.lang.String name, java.lang.ClassLoader loader); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 9] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 10] local: name index: 1 type: java.lang.String [pc: 0, pc: 10] local: loader index: 2 type: java.lang.ClassLoader // Method descriptor #37 ()Ljava/util/Enumeration; // Signature: ()Ljava/util/Enumeration<Ljava/lang/String;>; // Stack: 3, Locals: 1 public java.util.Enumeration entries(); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 10] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #30 ()V // Stack: 3, Locals: 1 protected void finalize() throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 11] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #42 (Ljava/lang/String;)Z public static native boolean isDexOptNeeded(java.lang.String arg0) throws java.io.FileNotFoundException, java.io.IOException; } Thanks

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  • Reusing OAuth request token when user refresh page - Twitter4j on GAE

    - by Tahir Akram
    Hi I am using Twitter4J API on GAE/J. I want to use the request token when user came to my page. (called back URL). And press refresh button. I write following code for that. But When user press refresh button. I got Authentication credentials error. Please see the stacktrance. It works fine when user first time used that token. HomeServlet.java code: HttpSession session = request.getSession(); twitter.setOAuthConsumer(FFConstants.CONSUMER_KEY, FFConstants.CONSUMER_SECRET); String token = (String) session.getAttribute("token"); String authorizedToken = (String)session.getAttribute("authorizedToken"); User user = null; if (!token.equals(authorizedToken)){ AccessToken accessToken = twitter.getOAuthAccessToken( token, (String) session .getAttribute("tokenSecret")); twitter.setOAuthAccessToken(accessToken); user = twitter.verifyCredentials(); session.setAttribute("authorizedToken", token); session.setAttribute("user", user); }else{ user = (User)session.getAttribute("user"); } TwitterUser twitterUser = new TwitterUser(); twitterUser.setFollowersCount(user.getFollowersCount()); twitterUser.setFriendsCount(user.getFriendsCount()); twitterUser.setFullName(user.getName()); twitterUser.setScreenName(user.getScreenName()); twitterUser.setLocation(user.getLocation()); Please suggest how I can do that. I have seen on many website. They retain the user with the same token. Even if user press browser refresh buttion again and again. Please help. Exception stacktrace: Reason: twitter4j.TwitterException: 401:Authentication credentials were missing or incorrect. /friends/ids.xml This method requires authentication. at twitter4j.http.HttpClient.httpRequest(HttpClient.java:469) at twitter4j.http.HttpClient.get(HttpClient.java:412) at twitter4j.Twitter.get(Twitter.java:276) at twitter4j.Twitter.get(Twitter.java:228) at twitter4j.Twitter.getFriendsIDs(Twitter.java:1819) at com.tff.servlet.HomeServlet.doGet(HomeServlet.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:693) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093) at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:712) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139) at org.mortbay.jetty.Server.handle(Server.java:313) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:506) at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:830) at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381) at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135) at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:235) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5235) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5233) at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24) at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:363) at com.google.net.rpc.impl.Server$2.run(Server.java:838) at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56) at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:536) at com.google.net.rpc.impl.Server.startRpc(Server.java:793) at com.google.net.rpc.impl.Server.processRequest(Server.java:368) at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:448) at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319) at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290) at com.google.net.async.Connection.handleReadEvent(Connection.java:466) at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:759) at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:205) at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:101) at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251) at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:394) at java.lang.Thread.run(Unknown Source)

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  • How much of slow and fast flash memory a "flash memory" have?

    - by gsc-frank
    Trying to know what is the best of my flash memories to use ReadyBoost I realize that I don't know how much of fast flash memory each of my flash drives have. One can read: In some situations, you might not be able to use all of the memory on your device to speed up your computer. For example, some flash memory devices contain both slow and fast flash memory, but ReadyBoost can only use fast flash memory to speed up your computer. From http://windows.microsoft.com/is-IS/windows7/Using-memory-in-your-storage-device-to-speed-up-your-computer

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  • How much of slow and fast flash memory a "flash memory" have? [migrated]

    - by gsc-frank
    Trying to know what is the best of my flash memories to use ReadyBoost I realize that I don't know how much of fast flash memory each of my flash drives have. One can read: In some situations, you might not be able to use all of the memory on your device to speed up your computer. For example, some flash memory devices contain both slow and fast flash memory, but ReadyBoost can only use fast flash memory to speed up your computer. From http://windows.microsoft.com/is-IS/windows7/Using-memory-in-your-storage-device-to-speed-up-your-computer

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  • Windows 7 memory usage

    - by lydonchandra
    Physical memory(MB) for Windows 7 Total 4021 Cached 1113 Available 768 Free 174 Memory used 3.25GB At this point, windows7 asks me to close some programs because "system memory is low". From my understanding reading articles, I still have 768 MB free memory, why does windows7 complain? Also what does Cached memory refer to? Is this part of memory that Windows7 reserved for itself meaning it's free to use by Windows7 (and means I have about 768 + 1113 MB of free mem?)?

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  • sysbench memory test on ec2 small instance

    - by caribio
    I'm seeing a problem with sysbench memory test (the default version that's compiled in). This is on Ubuntu Maverick, sysbench installed via apt-get install sysbench. Running the same thing on Ubuntu @ Rackspace worked just as expected. While the CPU and I/O tests worked fine on EC2 servers, the memory test just runs without doing anything (notice the 0M in the test results). The instance used was the publicly available 'stock' Ubuntu image with no changes to it: ./ec2-run-instances ami-ccf405a5 --instance-type m1.small --region us-east-1 --key mykey Supplying more arguments (such as: --memory-block-size=1K --memory-total-size=102400M) didn't help. What am I doing wrong? Thanks. sysbench --num-threads=4 --test=memory run sysbench 0.4.12: multi-threaded system evaluation benchmark Running the test with following options: Number of threads: 4 Doing memory operations speed test Memory block size: 1K Memory transfer size: 0M Memory operations type: write Memory scope type: global Threads started! Done. Operations performed: 0 ( 0.00 ops/sec) 0.00 MB transferred (0.00 MB/sec) Test execution summary: total time: 0.0003s total number of events: 0 total time taken by event execution: 0.0000 per-request statistics: min: 18446744073709.55ms avg: 0.00ms max: 0.00ms Threads fairness: events (avg/stddev): 0.0000/0.00 execution time (avg/stddev): 0.0000/0.00

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  • Linux released memory

    - by user59088
    If My process allocates some big memory and then deallocates, would top or gnome-system-monitor show that my memory usage of that process decreased ? or kernel will still reserve that memory for that process ? What I see is I am deallocating memory. But I still see gnome-system-monitor displaying growing memory for my program. I don't find memory leak in my end. I want to know whether its not displaying released memory ? or there is really a memory leak at my end ?

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  • What are the advantages of registered memory?

    - by odd parity
    I'm browsing for a few low-end servers for a startup and I'm a bit confused about the different memory types. The advantage of ECC is clear - single-bit error correction. When it comes to registered memory it seems more vague, especially in systems that support both registered and unbuffered memory. A Google search mostly finds copies of the Wikipedia article, which states that registered memory chips "...place less electrical load on the memory controller and allow single systems to remain stable with more memory modules than they would have otherwise". However I can't find any quantification of this. What I'm wondering about is: Is registered memory an improvement over unbuffered when it comes to soft error rate, or is it purely about the maximum number of modules supported? If yes, at what point (amount of modules or GB of memory) do these improvements start to become noticeable? For a specific example, the HP ProLiant DL 120 G6 server manual states that maximum supported memory configuration is 16 GB unbuffered (4x4GB) or 12 GB registered (6x2GB). In this case I'd rather have the extra 4GB of memory if the reliability difference is negligible.

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  • Calculating memory footprints using /proc/sysvipc/shm

    - by MarkTeehan
    This is for a SLES 10 database server. One of my servers runs three databases and three app servers; I am analyzing how their shared memory segments grow and shrink to avoid intermittent out-of-memory scenarios. "Top" is hot helpful for this since its calculations for RES and VIRT are inconsistent. I am doing this by matching up the contents of /proc/sysvipc/shm with memory usage reported by the database admin console. I do this by totaling up saving the contents of /proc/sysvipc/shm and then total up "bytes" for all of the segments for the offending userid. This is a large server with hundreds of segments and tens (or hundreds) of GB of allocated memory per userid. However it doesn't match up - the database management software claims to be using around 25% more memory than the total I calculate. Negligible swap space is in use, so I am ignoring that. I am running it as root so I am sure I see all shared memory segments. My question is : is all (significant) allocated memory recorded in /proc/sysvipc/shm, or is this only shared memory (*and not "un-shared" memory?). If this is incorrect, what is the correct way to calculate out the total allocated memory for each userid? Also: I believe doing a 'cat' on this file locks server IPC. I check it every 5 seconds - is it likely that this frequency could be problematic? Thanks! Mark Teehan Singapore

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  • Memory Usage in LINUX

    - by Incredible
    I have a debian system. It has 8GB memory. When I do top it shows 7.9 GB memory used and rest free. I add up the memory usage of all the programs running from top and they hardly sum up to around 50 MB. So, where is rest of the memory being used? Can I have a better detailed info of the memory usage? What is a better way to check the memory usage?

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  • Hibernate+PostgreSQL throws JDBCConnectionException: Cannot open connection

    - by Omer Salmanoglu
    false true auto thread org.postgresql.Driver 1234 jdbc:postgresql://localhost/postgres postgres public org.hibernate.dialect.PostgreSQLDialect false true org.hibernate.transaction.JDBCTransactionFactory false false false false 100 When I press "Save" button I get the following exception: javax.servlet.ServletException: org.hibernate.exception.JDBCConnectionException: Cannot open connection javax.faces.webapp.FacesServlet.service(FacesServlet.java:325) root cause javax.faces.el.EvaluationException: org.hibernate.exception.JDBCConnectionException: Cannot open connection javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312) root cause org.hibernate.exception.JDBCConnectionException: Cannot open connection org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:98) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52) org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449) org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167) org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142) org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85) org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) $Proxy108.beginTransaction(Unknown Source) com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.apache.el.parser.AstValue.invoke(AstValue.java:196) org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276) com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98) javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312) root cause java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost/postgres java.sql.DriverManager.getConnection(Unknown Source) java.sql.DriverManager.getConnection(Unknown Source) org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133) org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446) org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167) org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142) org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85) org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) $Proxy108.beginTransaction(Unknown Source) com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.apache.el.parser.AstValue.invoke(AstValue.java:196) org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276) com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98) javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)

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  • JSF HIBERNATE POSTGRESQL

    - by user312619
    When I press "Save" button I get an exception like that ; javax.servlet.ServletException: org.hibernate.exception.JDBCConnectionException: Cannot open connection javax.faces.webapp.FacesServlet.service(FacesServlet.java:325) root cause javax.faces.el.EvaluationException: org.hibernate.exception.JDBCConnectionException: Cannot open connection javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312) root cause org.hibernate.exception.JDBCConnectionException: Cannot open connection org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:98) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52) org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449) org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167) org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142) org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85) org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) $Proxy108.beginTransaction(Unknown Source) com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.apache.el.parser.AstValue.invoke(AstValue.java:196) org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276) com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98) javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312) root cause java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost/postgres java.sql.DriverManager.getConnection(Unknown Source) java.sql.DriverManager.getConnection(Unknown Source) org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133) org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446) org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167) org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142) org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85) org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) $Proxy108.beginTransaction(Unknown Source) com.yemex.beans.CompanyBean.saveOrUpdate(CompanyBean.java:52) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.apache.el.parser.AstValue.invoke(AstValue.java:196) org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276) com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98) javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88) com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) javax.faces.component.UICommand.broadcast(UICommand.java:315) javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)

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  • java.rmi.UnmarshalException: unable to pull client classes by server

    - by andrews
    Hi, I have an RMI client/server set-up on two machines that works fine in a simple situation when the server doesn't require a client-side defned class. However, when I need to use a class defined on the client side I am unable to have the server unmarshall those classes. I suspect this is an issue with my java.rmi.server.codebase property that I pass in as argument to the client app. I followed Sun's RMI Tutorial trail and I think I have followed the steps exactly except that I don't specify a classpath argument when executing client and server because they execute in the directory right above the root package directory (however I tried that too with no effect). The exceptions I get when attempting to execute the different client-side combinations described in detail below are all the same: RmiServer exception: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: java.lang.ClassNotFoundException: test.MyTask at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:353) at sun.rmi.transport.Transport$1.run(Transport.java:177) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:173) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy0.execute(Unknown Source) at test.myClient.main(myClient.java:32) The details are: My client/server rmi is set up over a home network behind a router. The router is assigned to a static ip address I will call myhostname. Appropriate port-mapping is set-up in the router that points to the right machines. role, machine, os, ip-address: server, venice, linux ubuntu 9.10, 10.0.1.2 client, naples, mac os x leopard, 10.0.1.4 I startup the server side as follows inside /home/andrews/workspace/epsilon/bin: 1 starting registry on the default port 1099: venice% rmiregistry & 2 starting web-server on port 2001 pointing to code base for common interfaces: venice% java webserver/ClassFileServer 2001 /home/andrew/workspace/epsilon/bin 3 starting server app (main class in test/myServer) which registers the server object: venice% java -Djava.rmi.server.codebase="http://myhostname:2001/" -Djava.security.policy=server.policy -Djava.rmi.server.hostname=myhostname test/myServer & Now the client side inside /Users/andrews/Development/Java/workspace/epsilon/bin: 1 start a local web server that can server client-side classes to the server (not sure if this is needed, but I added I tried it, and still no success; I have added port-mapping to the router for 2001 to venice, for 2002 to naples) naples$ java webserver/ClassFileServer 2002 /Users/andrews/Development/Java/workspace/epsilon/bin/ Trying to run the client (note: I don't specify the -cp argument because client executes right above the root package directory): 1 try #1 using an http hostname naples$ java -Djava.rmi.server.codebase=http://10.0.1.4:2002/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the myhostname argument at the end is passed-in to the client so that it resolves to server's rmi hostname. Note 2: I tried using localhost:2002 instead of 10.0.1.4:2002 too. Note 3: I tried using myhostname:2002 since myhostname is assigned to the router and I have proper port-mapping set-up, this address should resolve to naples and not venice 2 try #2: naples$ java -Djava.rmi.server.codebase=file:/Users/andrews/Development/Java/workspace/epsilon/bin/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the code base url format is correct, I created a small program to convert current file directory path into a url and used that. using file:///Users... has same effect. Other notes: 1 my server and client policy files correctly specify the path, as I've tested this setup with good and bad paths, and getting a security exception for bad path 2 this setup works if I don't use client-side defined objects, the client connects correctly to the server and the server executes. 3 when I place the client-side class on the server in the server's classpath, all executes fine. All help is appreciated.

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  • SQL SERVER – Weekly Series – Memory Lane – #052

    - by Pinal Dave
    Let us continue with the final episode of the Memory Lane Series. Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Set Server Level FILLFACTOR Using T-SQL Script Specifies a percentage that indicates how full the Database Engine should make the leaf level of each index page during index creation or alteration. fillfactor must be an integer value from 1 to 100. The default is 0. Limitation of Online Index Rebuld Operation Online operation means when online operations are happening in the database are in normal operational condition, the processes which are participating in online operations does not require exclusive access to the database. Get Permissions of My Username / Userlogin on Server / Database A few days ago, I was invited to one of the largest database company. I was asked to review database schema and propose changes to it. There was special username or user logic was created for me, so I can review their database. I was very much interested to know what kind of permissions I was assigned per server level and database level. I did not feel like asking Sr. DBA the question about permissions. Simple Example of WHILE Loop With CONTINUE and BREAK Keywords This question is one of those questions which is very simple and most of the users get it correct, however few users find it confusing for the first time. I have tried to explain the usage of simple WHILE loop in the first example. BREAK keyword will exit the stop the while loop and control is moved to the next statement after the while loop. CONTINUE keyword skips all the statement after its execution and control is sent to the first statement of while loop. Forced Parameterization and Simple Parameterization – T-SQL and SSMS When the PARAMETERIZATION option is set to FORCED, any literal value that appears in a SELECT, INSERT, UPDATE or DELETE statement is converted to a parameter during query compilation. When the PARAMETERIZATION database option is SET to SIMPLE, the SQL Server query optimizer may choose to parameterize the queries. 2008 Transaction and Local Variables – Swap Variables – Update All At Once Concept Summary : Transaction have no effect over memory variables. When UPDATE statement is applied over any table (physical or memory) all the updates are applied at one time together when the statement is committed. First of all I suggest that you read the article listed above about the effect of transaction on local variant. As seen there local variables are independent of any transaction effect. Simulate INNER JOIN using LEFT JOIN statement – Performance Analysis Just a day ago, while I was working with JOINs I find one interesting observation, which has prompted me to create following example. Before we continue further let me make very clear that INNER JOIN should be used where it cannot be used and simulating INNER JOIN using any other JOINs will degrade the performance. If there are scopes to convert any OUTER JOIN to INNER JOIN it should be done with priority. 2009 Introduction to Business Intelligence – Important Terms & Definitions Business intelligence (BI) is a broad category of application programs and technologies for gathering, storing, analyzing, and providing access to data from various data sources, thus providing enterprise users with reliable and timely information and analysis for improved decision making. Difference Between Candidate Keys and Primary Key Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as Primary Key. Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key. 2010 Taking Multiple Backup of Database in Single Command – Mirrored Database Backup I recently had a very interesting experience. In one of my recent consultancy works, I was told by our client that they are going to take the backup of the database and will also a copy of it at the same time. I expressed that it was surely possible if they were going to use a mirror command. In addition, they told me that whenever they take two copies of the database, the size of the database, is always reduced. Now this was something not clear to me, I said it was not possible and so I asked them to show me the script. Corrupted Backup File and Unsuccessful Restore The CTO, who was also present at the location, got very upset with this situation. He then asked when the last successful restore test was done. As expected, the answer was NEVER.There were no successful restore tests done before. During that time, I was present and I could clearly see the stress, confusion, carelessness and anger around me. I did not appreciate the feeling and I was pretty sure that no one in there wanted the atmosphere like me. 2011 TRACEWRITE – Wait Type – Wait Related to Buffer and Resolution SQL Trace is a SQL Server database engine technology which monitors specific events generated when various actions occur in the database engine. When any event is fired it goes through various stages as well various routes. One of the routes is Trace I/O Provider, which sends data to its final destination either as a file or rowset. DATEDIFF – Accuracy of Various Dateparts If you want to have accuracy in seconds, you need to use a different approach. In the first example, the accurate method is to find the number of seconds first and then divide it by 60 to convert it in minutes. Dedicated Access Control for SQL Server Express Edition http://www.youtube.com/watch?v=1k00z82u4OI Book Signing at SQLPASS 2012 Who I Am And How I Got Here – True Story as Blog Post If there was a shortcut to success – I want to know. I learnt SQL Server hard way and I am still learning. There are so many things, I have to learn. There is not enough time to learn everything which we want to learn. I am constantly working on it every day. I welcome you to join my journey as well. Please join me in my journey to learn SQL Server – more the merrier. Vacation, Travel and Study – A New Concept Even those who have advanced degrees and went to college for years, or even decades, find studying hard.  There is a difference between studying for a career and studying for a certification.  At least to get a degree there is a variety of subjects, with labs, exams, and practice problems to make things more interesting. Order By Numeric Values Formatted as String We have a table which has a column containing alphanumeric data. The data always has first as an integer and later part as a string. The business need is to order the data based on the first part of the alphanumeric data which is an integer. Now the problem is that no matter how we use ORDER BY the result is not produced as expected. Let us understand this with an example. Resolving SQL Server Connection Errors – SQL in Sixty Seconds #030 – Video One of the most famous errors related to SQL Server is about connecting to SQL Server itself. Here is how it goes, most of the time developers have worked with SQL Server and knows pretty much every error which they face during development language. However, hardly they install fresh SQL Server. As the installation of the SQL Server is a rare occasion unless you are a DBA who is responsible for such an instance – the error faced during installations are pretty rare as well. http://www.youtube.com/watch?v=1k00z82u4OI Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Weekly Series – Memory Lane – #034

    - by Pinal Dave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 UDF – User Defined Function to Strip HTML – Parse HTML – No Regular Expression The UDF used in the blog does fantastic task – it scans entire HTML text and removes all the HTML tags. It keeps only valid text data without HTML task. This is one of the quite commonly requested tasks many developers have to face everyday. De-fragmentation of Database at Operating System to Improve Performance Operating system skips MDF file while defragging the entire filesystem of the operating system. It is absolutely fine and there is no impact of the same on performance. Read the entire blog post for my conversation with our network engineers. Delay Function – WAITFOR clause – Delay Execution of Commands How do you delay execution of the commands in SQL Server – ofcourse by using WAITFOR keyword. In this blog post, I explain the same with the help of T-SQL script. Find Length of Text Field To measure the length of TEXT fields the function is DATALENGTH(textfield). Len will not work for text field. As of SQL Server 2005, developers should migrate all the text fields to VARCHAR(MAX) as that is the way forward. Retrieve Current Date Time in SQL Server CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} There are three ways to retrieve the current datetime in SQL SERVER. CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} Explanation and Comparison of NULLIF and ISNULL An interesting observation is NULLIF returns null if it comparison is successful, whereas ISNULL returns not null if its comparison is successful. In one way they are opposite to each other. Here is my question to you - How to create infinite loop using NULLIF and ISNULL? If this is even possible? 2008 Introduction to SERVERPROPERTY and example SERVERPROPERTY is a very interesting system function. It returns many of the system values. I use it very frequently to get different server values like Server Collation, Server Name etc. SQL Server Start Time We can use DMV to find out what is the start time of SQL Server in 2008 and later version. In this blog you can see how you can do the same. Find Current Identity of Table Many times we need to know what is the current identity of the column. I have found one of my developers using aggregated function MAX () to find the current identity. However, I prefer following DBCC command to figure out current identity. Create Check Constraint on Column Some time we just need to create a simple constraint over the table but I have noticed that developers do many different things to make table column follow rules than just creating constraint. I suggest constraint is a very useful concept and every SQL Developer should pay good attention to this subject. 2009 List Schema Name and Table Name for Database This is one of the blog post where I straight forward display script. One of the kind of blog posts, which I still love to read and write. Clustered Index on Separate Drive From Table Location A table devoid of primary key index is called heap, and here data is not arranged in a particular order, which gives rise to issues that adversely affect performance. Data must be stored in some kind of order. If we put clustered index on it then the order will be forced by that index and the data will be stored in that particular order. Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. 2010 Data Pages in Buffer Pool – Data Stored in Memory Cache One of my earlier year article, which I still read it many times and point developers to read it again. It is clear from the Resultset that when more than one index is used, datapages related to both or all of the indexes are stored in Memory Cache separately. TRANSACTION, DML and Schema Locks Can you create a situation where you can see Schema Lock? Well, this is a very simple question, however during the interview I notice over 50 candidates failed to come up with the scenario. In this blog post, I have demonstrated the situation where we can see the schema lock in database. 2011 Solution – Puzzle – Statistics are not updated but are Created Once In this example I have created following situation: Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated Auto Update Statistics and Auto Create Statistics for database is TRUE Now I have requested two things in the example 1) Why this is happening? 2) How to fix this issue? Selecting Domain from Email Address This is a straight to script blog post where I explain how to select only domain name from entire email address. Solution – Generating Zero Without using Any Numbers in T-SQL How to get zero digit without using any digit? This is indeed a very interesting question and the answer is even interesting. Try to come up with answer in next 10 minutes and if you can’t come up with the answer the blog post read this post for solution. 2012 Simple Explanation and Puzzle with SOUNDEX Function and DIFFERENCE Function In simple words - SOUNDEX converts an alphanumeric string to a four-character code to find similar-sounding words or names. DIFFERENCE function returns an integer value. The  integer returned is the number of characters in the SOUNDEX values that are the same. Read Only Files and SQL Server Management Studio (SSMS) I have come across a very interesting feature in SSMS related to “Read Only” files. I believe it is a little unknown feature as well so decided to write a blog about the same. Identifying Column Data Type of uniqueidentifier without Querying System Tables How do I know if any table has a uniqueidentifier column and what is its value without using any DMV or System Catalogues? Only information you know is the table name and you are allowed to return any kind of error if the table does not have uniqueidentifier column. Read the blog post to find the answer. Solution – User Not Able to See Any User Created Object in Tables – Security and Permissions Issue Interesting question – “When I try to connect to SQL Server, it lets me connect just fine as well let me open and explore the database. I noticed that I do not see any user created instances but when my colleague attempts to connect to the server, he is able to explore the database as well see all the user created tables and other objects. Can you help me fix it?” Importing CSV File Into Database – SQL in Sixty Seconds #018 – Video Here is interesting small 60 second video on how to import CSV file into Database. ColumnStore Index – Batch Mode vs Row Mode Here is the logic behind when Columnstore Index uses Batch Mode and when it uses Row Mode. A batch typically represents about 1000 rows of data. Batch mode processing also uses algorithms that are optimized for the multicore CPUs and increased memory throughput. Follow up – Usage of $rowguid and $IDENTITY This is an excellent follow up blog post of my earlier blog post where I explain where to use $rowguid and $identity.  If you do not know the difference between them, this is a blog with a script example. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • How to learn high-level Java web development concepts

    - by titaniumdecoy
    I have some experience writing web applications in Java for class projects. My first project used Servlets and my second, the Stripes framework. However, I feel that I am missing the greater picture of Java web development. I don't really understand the web.xml and context.xml files. I'm not sure what constitutes a Java EE application as opposed to a generic Java web application. I can't figure out how a bean is different from an ordinary Java class (POJO?) and how that differs from an Enterprise Java Bean (EJB). These are just the first few questions I could think of, but there are many more. What is a good way to learn how Java web applications function from the top down rather than simply how to develop an application with a specific framework? (Is there a book for this sort of thing?) Ultimately, I would like to understand Java web applications well enough to write my own framework.

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  • Appserver runs out of memory

    - by sarego
    We have been facing Out of Memory errors in our App server for sometime. We see the used heap size increasing gradually until finally it reaches the available heap in size. This happens every 3 weeks after which a server restart is needed to fix this. Upon analysis of the heap dumps we find the problem to be objects used in JSPs. Can JSP objects be the real cause of Appserver memory issues? How do we free up JSP objects (Objects which are being instantiated using usebean or other tags)? We have a clustered Websphere appserver with 2 nodes and an IHS.

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  • Error in java code.

    - by user243680
    I am getting the following error when i try to use a blue tooth dongle to transfer a video file from pc to mobile phone. does anyone know run: BlueCove log redirected to log4j log4j:WARN No appenders could be found for logger (com.intel.bluetooth). log4j:WARN Please initialize the log4j system properly. BlueCove version 2.1.0 on bluesoleil java.io.IOException: Device not discovered BlueCove stack shutdown completed at com.intel.bluetooth.BluetoothStackBlueSoleil.connectionRfOpenClientConnection(BluetoothStackBlueSoleil.java:361) at com.intel.bluetooth.BluetoothRFCommClientConnection.<init>(BluetoothRFCommClientConnection.java:37) at com.intel.bluetooth.MicroeditionConnector.openImpl(MicroeditionConnector.java:379) at com.intel.bluetooth.MicroeditionConnector.open(MicroeditionConnector.java:162) at javax.microedition.io.Connector.open(Connector.java:83) at de.avetana.obexsolo.OBEXConnector.open(OBEXConnector.java:103) at OBEXTest.main(OBEXTest.java:23)

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