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  • When encrypting data that is not an even multiple of the block size do I have to send a complete las

    - by WilliamKF
    If I am using a block cipher such as AES which has a block size of 128 bits, what do I do if my data is not an even multiple of 128 bits? I am working with packets of data and do not want to change the size of my packet when encrypting it, yet my data is not an even multiple of 128? Does the AES block cipher allow handling of a final block that is short without changing the size of my message once encrypted?

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  • Accessing HttpApplication.Application variables from a class

    - by Young Ninja
    I set up various global parameters in Global.asax, as such: Application["PagePolicies"] = "~/Lab/Policies.aspx"; Application["PageShare"] = "/Share.aspx"; Application["FileSearchQueries"] = Server.MapPath("~/Resources/SearchQueries.xml"); ... I have no problem accessing these variables form .ascx.cs or .aspx.cs file -- ie. files that are part of the Web content. However, I can't seem to access 'Application' from basic class objects (ie. standalone .cs files). I read somewhere to use a slight variations in .cs files, as follows, but it always comes throws an exception when in use: String file = (String)System.Web.HttpContext.Current.Application["FileSearchQueries"];

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  • How IBM Implement WebSphere Application Server SDK for Sun Solaris OS

    - by Eng Al-Rawabdeh
    I deploy the same application in IBM-WAS on different OS ( Windows , AIX and SUN-Solaris ) , SDK errors appeared on SDK for just Solaris OS , I refer some sites and it talk that the SDK on Solaris OS was build based on Sun SDK is it write ? so please I need to now if the IBM build the Solaris SDK from scratch or based on sun SDK ?? More Details : I Installed the same IBM WAS Application Server on two servers as the following : 1- Server1 - OS (AIX) 2- Server2 - OS ( Solaris) these two server on the same network and have the same configuration . Then I deploy Java Application ( X ) on both servers , the Application X was run on Server1 ( AIX ) without any problem but when I run the Application on Server 2 ( Solaris OS) I faced SDK issue . So I need to know what the difference between AIX WAS SDK and Solaris WAS SDK ?? Note : I try windows and it was run without any problem .

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  • Building an HTML5 App with ASP.NET

    - by Stephen Walther
    I’m teaching several JavaScript and ASP.NET workshops over the next couple of months (thanks everyone!) and I thought it would be useful for my students to have a really easy to use JavaScript reference. I wanted a simple interactive JavaScript reference and I could not find one so I decided to put together one of my own. I decided to use the latest features of JavaScript, HTML5 and jQuery such as local storage, offline manifests, and jQuery templates. What could be more appropriate than building a JavaScript Reference with JavaScript? You can try out the application by visiting: http://Superexpert.com/JavaScriptReference Because the app takes advantage of several advanced features of HTML5, it won’t work with Internet Explorer 6 (but really, you should stop using that browser). I have tested it with IE 8, Chrome 8, Firefox 3.6, and Safari 5. You can download the source for the JavaScript Reference application at the end of this article. Superexpert JavaScript Reference Let me provide you with a brief walkthrough of the app. When you first open the application, you see the following lookup screen: As you type the name of something from the JavaScript language, matching results are displayed: You can click the details link for any entry to view details for an entry in a modal dialog: Alternatively, you can click on any of the tabs -- Objects, Functions, Properties, Statements, Operators, Comments, or Directives -- to filter results by type of syntax. For example, you might want to see a list of all JavaScript built-in objects: You can login to the application to make modification to the application: After you login, you can add, update, or delete entries in the reference database: HTML5 Local Storage The application takes advantage of HTML5 local storage to store all of the reference entries on the local browser. IE 8, Chrome 8, Firefox 3.6, and Safari 5 all support local storage. When you open the application for the first time, all of the reference entries are transferred to the browser. The data is stored persistently. Even if you shutdown your computer and return to the application many days later, the data does not need to be transferred again. Whenever you open the application, the app checks with the server to see if any of the entries have been updated on the server. If there have been updates, then only the updates are transferred to the browser and the updates are merged with the existing entries in local storage. After the reference database has been transferred to your browser once, only changes are transferred in the future. You get two benefits from using local storage. First, the application loads very fast and works very fast after the data has been loaded once. The application does not query the server whenever you filter or view entries. All of the data is persisted in the browser. Second, you can browse the JavaScript reference even when you are not connected to the Internet (when you are on the proverbial airplane). The JavaScript Reference works as an offline application for browsers that support offline applications (unfortunately, not IE). When using Google Chrome, you can easily view the contents of local storage by selecting Tools, Developer Tools (CTRL-SHIFT I) and selecting Storage, Local Storage: The JavaScript Reference app stores two items in local storage: entriesLastUpdated and entries. HTML5 Offline App For browsers that support HTML5 offline applications – Chrome 8 and Firefox 3.6 but not Internet Explorer – you do not need to be connected to the Internet to use the JavaScript Reference. The JavaScript Reference can execute entirely on your machine just like any other desktop application. When you first open the application with Firefox, you are presented with the following warning: Notice the notification bar that asks whether you want to accept offline content. If you click the Allow button then all of the files (generated ASPX, images, CSS, JavaScript) needed for the JavaScript Reference will be stored on your local computer. Automatic Script Minification and Combination All of the custom JavaScript files are combined and minified automatically whenever the application is built with Visual Studio. All of the custom scripts are contained in a folder named App_Scripts: When you perform a build, the combine.js and combine.debug.js files are generated. The Combine.config file contains the list of files that should be combined (importantly, it specifies the order in which the files should be combined). Here’s the contents of the Combine.config file:   <?xml version="1.0"?> <combine> <scripts> <file path="compat.js" /> <file path="storage.js" /> <file path="serverData.js" /> <file path="entriesHelper.js" /> <file path="authentication.js" /> <file path="default.js" /> </scripts> </combine>   jQuery and jQuery UI The JavaScript Reference application takes heavy advantage of jQuery and jQuery UI. In particular, the application uses jQuery templates to format and display the reference entries. Each of the separate templates is stored in a separate ASP.NET user control in a folder named Templates: The contents of the user controls (and therefore the templates) are combined in the default.aspx page: <!-- Templates --> <user:EntryTemplate runat="server" /> <user:EntryDetailsTemplate runat="server" /> <user:BrowsersTemplate runat="server" /> <user:EditEntryTemplate runat="server" /> <user:EntryDetailsCloudTemplate runat="server" /> When the default.aspx page is requested, all of the templates are retrieved in a single page. WCF Data Services The JavaScript Reference application uses WCF Data Services to retrieve and modify database data. The application exposes a server-side WCF Data Service named EntryService.svc that supports querying, adding, updating, and deleting entries. jQuery Ajax calls are made against the WCF Data Service to perform the database operations from the browser. The OData protocol makes this easy. Authentication is handled on the server with a ChangeInterceptor. Only authenticated users are allowed to update the JavaScript Reference entry database. JavaScript Unit Tests In order to build the JavaScript Reference application, I depended on JavaScript unit tests. I needed the unit tests, in particular, to write the JavaScript merge functions which merge entry change sets from the server with existing entries in browser local storage. In order for unit tests to be useful, they need to run fast. I ran my unit tests after each build. For this reason, I did not want to run the unit tests within the context of a browser. Instead, I ran the unit tests using server-side JavaScript (the Microsoft Script Control). The source code that you can download at the end of this blog entry includes a project named JavaScriptReference.UnitTests that contains all of the JavaScripts unit tests. JavaScript Integration Tests Because not every feature of an application can be tested by unit tests, the JavaScript Reference application also includes integration tests. I wrote the integration tests using Selenium RC in combination with ASP.NET Unit Tests. The Selenium tests run against all of the target browsers for the JavaScript Reference application: IE 8, Chrome 8, Firefox 3.6, and Safari 5. For example, here is the Selenium test that checks whether authenticating with a valid user name and password correctly switches the application to Admin Mode: [TestMethod] [HostType("ASP.NET")] [UrlToTest("http://localhost:26303/JavaScriptReference")] [AspNetDevelopmentServerHost(@"C:\Users\Stephen\Documents\Repos\JavaScriptReference\JavaScriptReference\JavaScriptReference", "/JavaScriptReference")] public void TestValidLogin() { // Run test for each controller foreach (var controller in this.Controllers) { var selenium = controller.Value; var browserName = controller.Key; // Open reference page. selenium.Open("http://localhost:26303/JavaScriptReference/default.aspx"); // Click login button displays login form selenium.Click("btnLogin"); Assert.IsTrue(selenium.IsVisible("loginForm"), "Login form appears after clicking btnLogin"); // Enter user name and password selenium.Type("userName", "Admin"); selenium.Type("password", "secret"); selenium.Click("btnDoLogin"); // Should set adminMode == true selenium.WaitForCondition("selenium.browserbot.getCurrentWindow().adminMode==true", "30000"); } }   The results for running the Selenium tests appear in the Test Results window just like the unit tests: The Selenium tests take much longer to execute than the unit tests. However, they provide test coverage for actual browsers. Furthermore, if you are using Visual Studio ALM, you can run the tests automatically every night as part of your standard nightly build. You can view the Selenium tests by opening the JavaScriptReference.QATests project. Summary I plan to write more detailed blog entries about this application over the next week. I want to discuss each of the features – HTML5 local storage, HTML5 offline apps, jQuery templates, automatic script combining and minification, JavaScript unit tests, Selenium tests -- in more detail. You can download the source control for the JavaScript Reference Application by clicking the following link: Download You need Visual Studio 2010 and ASP.NET 4 to build the application. Before running the JavaScript unit tests, install the Microsoft Script Control. Before running the Selenium tests, start the Selenium server by running the StartSeleniumServer.bat file located in the JavaScriptReference.QATests project.

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  • iPhone :Can we add more than One application in a Single application

    - by iPhone Fun
    Hi all, I do have an Idea to integrate with my application. I want to create multiple application within a single one application. Like and application containing Weather application as well as image processing application + camera based application. I want to know Is this thing possible with iphone application? Please suggest me is this possible with iPhone app development and is it allowed by apple or not. thanks for your suggestion in advance.

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  • IIS 7.5, Multiple Application Pools, and URL Rewriting (403.18 -- Forbidden)

    - by Jerry Hewett
    Is there any way to configure IIS 7.5 to perform URL rewrites to different application pools on the same site without running into a 403.18 error? We're using Helicon ISAPI Rewrite 3 on IIS 6 and it's working like a charm. The root-level "application" is running under it's own application pool, and on IIS 6 we have no problems doing URL rewrites from that application pool to any one of the other four application pools. But when I copy the same server configuration information over to IIS 7.5 the URL rewrites to any of the other application pools fail with a "403.18 -- Forbidden" error. The weird bit is that the IIS 6 is not (at least as far as I can tell, by looking at the site Service configuration dialog) running under IIS 5 emulation mode, so somehow the rewrites aren't throwing 403.18 errors. So something must be different... but whatever it is, I sure haven't been able to figure it out. Btw, we're not married to Helicon ISAPI Rewrite. If there's another way to preserve our current rewrite configuration rules using another module or method I'd be more than happy to use it.

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  • IIS 7.5, Multiple Application Pools, and URL Rewriting (403.18 -- Forbidden)

    - by Jerry Hewett
    Is there any way to configure IIS 7.5 to perform URL rewrites to different application pools on the same site without running into a 403.18 error? We're using Helicon ISAPI Rewrite 3 on IIS 6 and it's working like a charm. The root-level "application" is running under it's own application pool, and on IIS 6 we have no problems doing URL rewrites from that application pool to any one of the other four application pools. But when I copy the same server configuration information over to IIS 7.5 the URL rewrites to any of the other application pools fail with a "403.18 -- Forbidden" error. The weird bit is that the IIS 6 is not (at least as far as I can tell, by looking at the site Service configuration dialog) running under IIS 5 emulation mode, so somehow the rewrites aren't throwing 403.18 errors. So something must be different... but whatever it is, I sure haven't been able to figure it out. Btw, we're not married to Helicon ISAPI Rewrite. If there's another way to preserve our current rewrite configuration rules using another module or method I'd be more than happy to use it.

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  • Distributing processing for an application that wasn't designed with that in mind

    - by Tim
    We've got the application at work that just sits and does a whole bunch of iterative processing on some data files to perform some simulations. This is done by an "old" Win32 application that isn't multi-processor aware, so new(ish) computers and workstations are mostly sitting idle running this application. However, since it's installed by a typical Windows Install Shield installer, I can't seem to install and run multiple copies of the application. The work can be split up manually before processing, enabling the work to be distributed across multiple machines, but we still can't take advantage of multiple core CPUs. The results can be joined back together after processing to make a complete simulation. Is there a product out there that would let me "compartmentalize" an installation (or 4) so I can take advantage of a multi-core CPU? I had thought of using MS Softgrid, but I believe that still depends on a remote server to do the heavy lifting (though please correct me if I'm wrong). Furthermore, is there a way I can distribute the workload off the one machine? So an input could be split into 50 chunks, handed out to 50 machines, and worked on? All without really changing the initial application? In a perfect world, I'd get the application to take advantage of a DesktopGrid (BOINC), but like most "mission critical corporate applications", the need is there, but the money is not. Thank you in advance (and sorry if this isn't appropriate for serverfault).

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  • Application Virtualization

    - by Peter Versnee
    I have been looking for a solution to virtualize my desktop application as a SaaS. After picking Citrix XenApp as the best solution for my case and trying for ever to get it to work (with some more experienced people) I can't help but to conclude that Citrix has too much problems for my case. Every time I fix one thing some other thing pops up. As I can't imagine Citrix XenApp is the only way to deliver my application to my clients, I'd like to ask you experienced guys if you think there is an other way to deliver it whilst meeting my requirements. I've got no money issues - time on the other hand... My requirements: My application must run on a windows server; The application should be virtualized with the application window only (no desktop); Content Redirection (my application is the only one virtualized, so PDF, DOC(X) etc. is on the users' system); Easy user management; SSO;* Cross platform (Windows, Linux, Mac OSX).* I truly hope I don't annoy you with another of the same question. I've tried to find the same question here and - obviously - didn't found it. *) these I can live without, however very much appreciated

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  • Turn off LogEnabled Filter at run time - Logging Enterprise Application Block

    - by Or A
    Hi, so the story go like this: i'm using the Logging Enterprise Application block that provided by microsoft to log events in our application. The goal is to enabled event viewer logging at loading and then turn it off. What i did is to add EventLog TraceListener which write all our logs into the event viewer. What i'm trying to do is to disable it after the application was done loading. The only way that i can thing about is to add a LogEnabled Filter and then turn it off. However, i don't know how to access this filter at run time and disable log on this listener. if you have an idea, please share. Thanks

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  • Is having functionality in DB a road block to scalability?

    - by Estefany Velez
    I may not be able to give the right title to the question. But here it is, We are developing financial portal for wealth management. We are expecting over 10000 clients to use the application. The portal calculates various performance analytics based on the the technical analysis of the stock market. We developed lot of the functionality through Stored procedures, user defined functions, triggers etc. through Database. We thought we can gain huge performance boost doing stuff directly in database than through C# code. And we actually did get a huge performance boost. When I tried to brag about the achievement to our CTO, he counter questioned my decision of having functionality implemented in database rather than code. According to him such applications suffer scalability problems. In his words "These days things are kept in memory/cache. Clustered data is hard to manage over time. Facebook, Google have nothing in database. It is the era of thin servers and thick clients. DB is used only to store plain data and functionality should be completely decoupled from the database." Can you guys please give me some suggestions as to whether what he says is right. How to go about architect such an application?

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  • SQL SERVER – Database Dynamic Caching by Automatic SQL Server Performance Acceleration

    - by pinaldave
    My second look at SafePeak’s new version (2.1) revealed to me few additional interesting features. For those of you who hadn’t read my previous reviews SafePeak and not familiar with it, here is a quick brief: SafePeak is in business of accelerating performance of SQL Server applications, as well as their scalability, without making code changes to the applications or to the databases. SafePeak performs database dynamic caching, by caching in memory result sets of queries and stored procedures while keeping all those cache correct and up to date. Cached queries are retrieved from the SafePeak RAM in microsecond speed and not send to the SQL Server. The application gets much faster results (100-500 micro seconds), the load on the SQL Server is reduced (less CPU and IO) and the application or the infrastructure gets better scalability. SafePeak solution is hosted either within your cloud servers, hosted servers or your enterprise servers, as part of the application architecture. Connection of the application is done via change of connection strings or adding reroute line in the c:\windows\system32\drivers\etc\hosts file on all application servers. For those who would like to learn more on SafePeak architecture and how it works, I suggest to read this vendor’s webpage: SafePeak Architecture. More interesting new features in SafePeak 2.1 In my previous review of SafePeak new I covered the first 4 things I noticed in the new SafePeak (check out my article “SQLAuthority News – SafePeak Releases a Major Update: SafePeak version 2.1 for SQL Server Performance Acceleration”): Cache setup and fine-tuning – a critical part for getting good caching results Database templates Choosing which database to cache Monitoring and analysis options by SafePeak Since then I had a chance to play with SafePeak some more and here is what I found. 5. Analysis of SQL Performance (present and history): In SafePeak v.2.1 the tools for understanding of performance became more comprehensive. Every 15 minutes SafePeak creates and updates various performance statistics. Each query (or a procedure execute) that arrives to SafePeak gets a SQL pattern, and after it is used again there are statistics for such pattern. An important part of this product is that it understands the dependencies of every pattern (list of tables, views, user defined functions and procs). From this understanding SafePeak creates important analysis information on performance of every object: response time from the database, response time from SafePeak cache, average response time, percent of traffic and break down of behavior. One of the interesting things this behavior column shows is how often the object is actually pdated. The break down analysis allows knowing the above information for: queries and procedures, tables, views, databases and even instances level. The data is show now on all arriving queries, both read queries (that can be cached), but also any types of updates like DMLs, DDLs, DCLs, and even session settings queries. The stats are being updated every 15 minutes and SafePeak dashboard allows going back in time and investigating what happened within any time frame. 6. Logon trigger, for making sure nothing corrupts SafePeak cache data If you have an application with many parts, many servers many possible locations that can actually update the database, or the SQL Server is accessible to many DBAs or software engineers, each can access some database directly and do some changes without going thru SafePeak – this can create a potential corruption of the data stored in SafePeak cache. To make sure SafePeak cache is correct it needs to get all updates to arrive to SafePeak, and if a DBA will access the database directly and do some changes, for example, then SafePeak will simply not know about it and will not clean SafePeak cache. In the new version, SafePeak brought a new feature called “Logon Trigger” to solve the above challenge. By special click of a button SafePeak can deploy a special server logon trigger (with a CLR object) on your SQL Server that actually monitors all connections and informs SafePeak on any connection that is coming not from SafePeak. In SafePeak dashboard there is an interface that allows to control which logins can be ignored based on login names and IPs, while the rest will invoke cache cleanup of SafePeak and actually locks SafePeak cache until this connection will not be closed. Important to note, that this does not interrupt any logins, only informs SafePeak on such connection. On the Dashboard screen in SafePeak you will be able to see those connections and then decide what to do with them. Configuration of this feature in SafePeak dashboard can be done here: Settings -> SQL instances management -> click on instance -> Logon Trigger tab. Other features: 7. User management ability to grant permissions to someone without changing its configuration and only use SafePeak as performance analysis tool. 8. Better reports for analysis of performance using 15 minute resolution charts. 9. Caching of client cursors 10. Support for IPv6 Summary SafePeak is a great SQL Server performance acceleration solution for users who want immediate results for sites with performance, scalability and peak spikes challenges. Especially if your apps are packaged or 3rd party, since no code changes are done. SafePeak can significantly increase response times, by reducing network roundtrip to the database, decreasing CPU resource usage, eliminating I/O and storage access. SafePeak team provides a free fully functional trial www.safepeak.com/download and actually provides a one-on-one assistance during such trial. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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  • Plan Caching and Query Memory Part I – When not to use stored procedure or other plan caching mechanisms like sp_executesql or prepared statement

    - by sqlworkshops
      The most common performance mistake SQL Server developers make: SQL Server estimates memory requirement for queries at compilation time. This mechanism is fine for dynamic queries that need memory, but not for queries that cache the plan. With dynamic queries the plan is not reused for different set of parameters values / predicates and hence different amount of memory can be estimated based on different set of parameter values / predicates. Common memory allocating queries are that perform Sort and do Hash Match operations like Hash Join or Hash Aggregation or Hash Union. This article covers Sort with examples. It is recommended to read Plan Caching and Query Memory Part II after this article which covers Hash Match operations.   When the plan is cached by using stored procedure or other plan caching mechanisms like sp_executesql or prepared statement, SQL Server estimates memory requirement based on first set of execution parameters. Later when the same stored procedure is called with different set of parameter values, the same amount of memory is used to execute the stored procedure. This might lead to underestimation / overestimation of memory on plan reuse, overestimation of memory might not be a noticeable issue for Sort operations, but underestimation of memory will lead to spill over tempdb resulting in poor performance.   This article covers underestimation / overestimation of memory for Sort. Plan Caching and Query Memory Part II covers underestimation / overestimation for Hash Match operation. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   To read additional articles I wrote click here.   In most cases it is cheaper to pay for the compilation cost of dynamic queries than huge cost for spill over tempdb, unless memory requirement for a stored procedure does not change significantly based on predicates.   The best way to learn is to practice. To create the below tables and reproduce the behavior, join the mailing list by using this link: www.sqlworkshops.com/ml and I will send you the table creation script. Most of these concepts are also covered in our webcasts: www.sqlworkshops.com/webcasts   Enough theory, let’s see an example where we sort initially 1 month of data and then use the stored procedure to sort 6 months of data.   Let’s create a stored procedure that sorts customers by name within certain date range.   --Example provided by www.sqlworkshops.com create proc CustomersByCreationDate @CreationDateFrom datetime, @CreationDateTo datetime as begin       declare @CustomerID int, @CustomerName varchar(48), @CreationDate datetime       select @CustomerName = c.CustomerName, @CreationDate = c.CreationDate from Customers c             where c.CreationDate between @CreationDateFrom and @CreationDateTo             order by c.CustomerName       option (maxdop 1)       end go Let’s execute the stored procedure initially with 1 month date range.   set statistics time on go --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-01-31' go The stored procedure took 48 ms to complete.     The stored procedure was granted 6656 KB based on 43199.9 rows being estimated.       The estimated number of rows, 43199.9 is similar to actual number of rows 43200 and hence the memory estimation should be ok.       There was no Sort Warnings in SQL Profiler.      Now let’s execute the stored procedure with 6 month date range. --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-06-30' go The stored procedure took 679 ms to complete.      The stored procedure was granted 6656 KB based on 43199.9 rows being estimated.      The estimated number of rows, 43199.9 is way different from the actual number of rows 259200 because the estimation is based on the first set of parameter value supplied to the stored procedure which is 1 month in our case. This underestimation will lead to sort spill over tempdb, resulting in poor performance.      There was Sort Warnings in SQL Profiler.    To monitor the amount of data written and read from tempdb, one can execute select num_of_bytes_written, num_of_bytes_read from sys.dm_io_virtual_file_stats(2, NULL) before and after the stored procedure execution, for additional information refer to the webcast: www.sqlworkshops.com/webcasts.     Let’s recompile the stored procedure and then let’s first execute the stored procedure with 6 month date range.  In a production instance it is not advisable to use sp_recompile instead one should use DBCC FREEPROCCACHE (plan_handle). This is due to locking issues involved with sp_recompile, refer to our webcasts for further details.   exec sp_recompile CustomersByCreationDate go --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-06-30' go Now the stored procedure took only 294 ms instead of 679 ms.    The stored procedure was granted 26832 KB of memory.      The estimated number of rows, 259200 is similar to actual number of rows of 259200. Better performance of this stored procedure is due to better estimation of memory and avoiding sort spill over tempdb.      There was no Sort Warnings in SQL Profiler.       Now let’s execute the stored procedure with 1 month date range.   --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-01-31' go The stored procedure took 49 ms to complete, similar to our very first stored procedure execution.     This stored procedure was granted more memory (26832 KB) than necessary memory (6656 KB) based on 6 months of data estimation (259200 rows) instead of 1 month of data estimation (43199.9 rows). This is because the estimation is based on the first set of parameter value supplied to the stored procedure which is 6 months in this case. This overestimation did not affect performance, but it might affect performance of other concurrent queries requiring memory and hence overestimation is not recommended. This overestimation might affect performance Hash Match operations, refer to article Plan Caching and Query Memory Part II for further details.    Let’s recompile the stored procedure and then let’s first execute the stored procedure with 2 day date range. exec sp_recompile CustomersByCreationDate go --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-01-02' go The stored procedure took 1 ms.      The stored procedure was granted 1024 KB based on 1440 rows being estimated.      There was no Sort Warnings in SQL Profiler.      Now let’s execute the stored procedure with 6 month date range. --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-06-30' go   The stored procedure took 955 ms to complete, way higher than 679 ms or 294ms we noticed before.      The stored procedure was granted 1024 KB based on 1440 rows being estimated. But we noticed in the past this stored procedure with 6 month date range needed 26832 KB of memory to execute optimally without spill over tempdb. This is clear underestimation of memory and the reason for the very poor performance.      There was Sort Warnings in SQL Profiler. Unlike before this was a Multiple pass sort instead of Single pass sort. This occurs when granted memory is too low.      Intermediate Summary: This issue can be avoided by not caching the plan for memory allocating queries. Other possibility is to use recompile hint or optimize for hint to allocate memory for predefined date range.   Let’s recreate the stored procedure with recompile hint. --Example provided by www.sqlworkshops.com drop proc CustomersByCreationDate go create proc CustomersByCreationDate @CreationDateFrom datetime, @CreationDateTo datetime as begin       declare @CustomerID int, @CustomerName varchar(48), @CreationDate datetime       select @CustomerName = c.CustomerName, @CreationDate = c.CreationDate from Customers c             where c.CreationDate between @CreationDateFrom and @CreationDateTo             order by c.CustomerName       option (maxdop 1, recompile)       end go Let’s execute the stored procedure initially with 1 month date range and then with 6 month date range. --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-01-30' exec CustomersByCreationDate '2001-01-01', '2001-06-30' go The stored procedure took 48ms and 291 ms in line with previous optimal execution times.      The stored procedure with 1 month date range has good estimation like before.      The stored procedure with 6 month date range also has good estimation and memory grant like before because the query was recompiled with current set of parameter values.      The compilation time and compilation CPU of 1 ms is not expensive in this case compared to the performance benefit.     Let’s recreate the stored procedure with optimize for hint of 6 month date range.   --Example provided by www.sqlworkshops.com drop proc CustomersByCreationDate go create proc CustomersByCreationDate @CreationDateFrom datetime, @CreationDateTo datetime as begin       declare @CustomerID int, @CustomerName varchar(48), @CreationDate datetime       select @CustomerName = c.CustomerName, @CreationDate = c.CreationDate from Customers c             where c.CreationDate between @CreationDateFrom and @CreationDateTo             order by c.CustomerName       option (maxdop 1, optimize for (@CreationDateFrom = '2001-01-01', @CreationDateTo ='2001-06-30'))       end go Let’s execute the stored procedure initially with 1 month date range and then with 6 month date range.   --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-01-30' exec CustomersByCreationDate '2001-01-01', '2001-06-30' go The stored procedure took 48ms and 291 ms in line with previous optimal execution times.    The stored procedure with 1 month date range has overestimation of rows and memory. This is because we provided hint to optimize for 6 months of data.      The stored procedure with 6 month date range has good estimation and memory grant because we provided hint to optimize for 6 months of data.       Let’s execute the stored procedure with 12 month date range using the currently cashed plan for 6 month date range. --Example provided by www.sqlworkshops.com exec CustomersByCreationDate '2001-01-01', '2001-12-31' go The stored procedure took 1138 ms to complete.      2592000 rows were estimated based on optimize for hint value for 6 month date range. Actual number of rows is 524160 due to 12 month date range.      The stored procedure was granted enough memory to sort 6 month date range and not 12 month date range, so there will be spill over tempdb.      There was Sort Warnings in SQL Profiler.      As we see above, optimize for hint cannot guarantee enough memory and optimal performance compared to recompile hint.   This article covers underestimation / overestimation of memory for Sort. Plan Caching and Query Memory Part II covers underestimation / overestimation for Hash Match operation. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   Summary: Cached plan might lead to underestimation or overestimation of memory because the memory is estimated based on first set of execution parameters. It is recommended not to cache the plan if the amount of memory required to execute the stored procedure has a wide range of possibilities. One can mitigate this by using recompile hint, but that will lead to compilation overhead. However, in most cases it might be ok to pay for compilation rather than spilling sort over tempdb which could be very expensive compared to compilation cost. The other possibility is to use optimize for hint, but in case one sorts more data than hinted by optimize for hint, this will still lead to spill. On the other side there is also the possibility of overestimation leading to unnecessary memory issues for other concurrently executing queries. In case of Hash Match operations, this overestimation of memory might lead to poor performance. When the values used in optimize for hint are archived from the database, the estimation will be wrong leading to worst performance, so one has to exercise caution before using optimize for hint, recompile hint is better in this case. I explain these concepts with detailed examples in my webcasts (www.sqlworkshops.com/webcasts), I recommend you to watch them. The best way to learn is to practice. To create the above tables and reproduce the behavior, join the mailing list at www.sqlworkshops.com/ml and I will send you the relevant SQL Scripts.     Register for the upcoming 3 Day Level 400 Microsoft SQL Server 2008 and SQL Server 2005 Performance Monitoring & Tuning Hands-on Workshop in London, United Kingdom during March 15-17, 2011, click here to register / Microsoft UK TechNet.These are hands-on workshops with a maximum of 12 participants and not lectures. For consulting engagements click here.     Disclaimer and copyright information:This article refers to organizations and products that may be the trademarks or registered trademarks of their various owners. Copyright of this article belongs to R Meyyappan / www.sqlworkshops.com. You may freely use the ideas and concepts discussed in this article with acknowledgement (www.sqlworkshops.com), but you may not claim any of it as your own work. This article is for informational purposes only; you use any of the suggestions given here entirely at your own risk.   R Meyyappan [email protected] LinkedIn: http://at.linkedin.com/in/rmeyyappan

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  • How To Block Web Sites at the Router Level for Network Wide Filtering

    - by Jason Fitzpatrick
    A comprehensive network filtering system is overkill if all you want to do is block a handful of web sites. Read on as we show you how—with nothing more than your router—you can selectively block and temporarily restrict individual websites. For many people a massive commercial internet filter is overkill. What if you just want to block Facebook when your kids are supposed to be doing their homework or Reddit when you’re supposed to be getting work done? You don’t need a huge system for that, all you need is the access restrictions module in your router. Today we’re looking at how you can quickly and easily block traffic on your network using router-based access restrictions. HTG Explains: When Do You Need to Update Your Drivers? How to Make the Kindle Fire Silk Browser *Actually* Fast! Amazon’s New Kindle Fire Tablet: the How-To Geek Review

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  • Per-machine decentralised DNS caching - nscd/lwresd/etc

    - by Dan Carley
    Preface: We have caching resolvers at each of our geographic network locations. These are clustered for resiliency and their locality reduces the latency of internal requests generated by our servers. This works well. Except that a vast quantity of the requests seen over the wire are lookups for the same records, generated by applications which don't perform any DNS caching of their own. Questions: Is there a significant benefit to running lightweight caching daemons on the individual servers in order to reduce repeated requests from hitting the network? Does anyone have experience of using [u]nscd, lwresd or dnscache to do such a thing? Are there any other packages worth looking at? Any caveats to beware of? Besides the obvious, caching and negative caching stale results.

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  • Caching DNS server (bind9.2) CPU usage is so so so high.

    - by Gk
    Hi, I have a caching-only dns server which get ~3k queries per second. Here is specs: Xeon dual-core 2,8GHz 4GB of RAM Centos 5x (kernel 2.6.18-164.15.1.el5PAE) bind 9.4.2 rndc status: recursive clients: 666/4900/5000 About 300 new queries (not in cache) per second. Bind always uses 100% on one core on single-thread config. After I recompiled it to multi-thread, it uses nearly 200% on two core :( No iowait, only sys and user. I searched around but didn't see any info about how bind use CPU. Why does it become bottleneck? One more thing, here is RAM usage: cat /proc/meminfo MemTotal: 4147876 kB MemFree: 1863972 kB Buffers: 143632 kB Cached: 372792 kB SwapCached: 0 kB Active: 1916804 kB Inactive: 276056 kB I've set max-cache-size to 0 to make sure bind can use as much RAM as it want, but it always stop at ~2GB. Since every second we got not cached queries so theoretically RAM must be exhausted but it wasn't. Do you have any idea? TIA, -Gk

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  • What advantages does developing applications for smartphones have over developing the same application as a web application?

    - by Alfredo O
    Let's take the Facebook application as an example. Why did they develop an application when the users could just access to their page and do the same? For me that represents more maintenance and more cost because for each feature added to the web application that feature will have to be added to the smartphone application as well. So why would I want to develop more than once (for each patform iOS, Android, etc) when I could just have one web application? What benefits do I get? The only one that comes to my mind is GPS feature. EDIT: My question is more oriented towards business applications that are going to be used only by some members of the company, it's not about selling the application (private use). So contrary to what some answers say about that by developing as a smartphone application it will benefit from more sells because of the "smartphone stores" for me this point is not important because the application is for private use. By developing the application as a web application it means that it can be accessed through smartphone browser and also in a PC (any capable browser), but developing as a native application would limit this to only some kind of smartphone so we would be limiting the use. On the other hand developing it as a web application means that in order to access the application an Internet connection must be available. So keeping this in mind how would you convince your boss to write the application for a given smartphone platform (iOS/Android) vs developing it as a web application?

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  • Best way to block a country by IP address?

    - by George Edison
    I have a website that needs to block a particular country based on IP address. I am more than aware that IP-based blocking is not a foolproof method for blocking visitors, but it is a necessary step in the right direction. Since I'm using PHP, what I would do is use a GeoIP database like geoplugin.net. However, I'm curious to know if there's a better way of doing this. The website is on a shared webserver (I don't have root access) and it is running Apache on centOS. I guess my question is "can an .htaccess file be configured to block by IP using an external source to lookup IP addresses."

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