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  • Silverlight 4 + RIA Services - Ready for Business: Validating Data

      To continue our series lets look at data validation our business applications. Updating data is great, but when you enable data update you often need to check the data to ensure it is valid.  RIA Services as clean, prescriptive pattern for handling this.   First lets look at what you get for free.  The value for any field entered has to be valid for the range of that data type.  For example, you never need to write code to ensure someone didnt type is forty-two into...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Should Business Interfaces be part of the Model layer?

    - by Mik378
    In an oriented-services enterprise application, isn't it an antipattern to mix Service APIs (containing interface that external users depends on) with Model objects (entities, custom exceptions objects etc...) ? According to me, Services should only depends on Model layer but never mixed with it. In fact, my colleague told me that it doesn't make sense to separate it since client need both. (model and service interfaces) But I notice that everytime a client asks for some changes, like adding a new method in some interface (means a new service), Model layer has to be also delivered... Thus, client who has not interested by this "addition" is constrained to be concerned by this update of Model... and in a large enterprise application, this kind of delivery is known to be very risked... What is the best practice ? Separate services(only interfaces so) and model objects or mix it ?

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  • Plagued by multithreaded bugs

    - by koncurrency
    On my new team that I manage, the majority of our code is platform, TCP socket, and http networking code. All C++. Most of it originated from other developers that have left the team. The current developers on the team are very smart, but mostly junior in terms of experience. Our biggest problem: multi-threaded concurrency bugs. Most of our class libraries are written to be asynchronous by use of some thread pool classes. Methods on the class libraries often enqueue long running taks onto the thread pool from one thread and then the callback methods of that class get invoked on a different thread. As a result, we have a lot of edge case bugs involving incorrect threading assumptions. This results in subtle bugs that go beyond just having critical sections and locks to guard against concurrency issues. What makes these problems even harder is that the attempts to fix are often incorrect. Some mistakes I've observed the team attempting (or within the legacy code itself) includes something like the following: Common mistake #1 - Fixing concurrency issue by just put a lock around the shared data, but forgetting about what happens when methods don't get called in an expected order. Here's a very simple example: void Foo::OnHttpRequestComplete(statuscode status) { m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } So now we have a bug in which Shutdown could get called while OnHttpNetworkRequestComplete is occuring on. A tester finds the bug, captures the crash dump, and assigns the bug to a developer. He in turn fixes the bug like this. void Foo::OnHttpRequestComplete(statuscode status) { AutoLock lock(m_cs); m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { AutoLock lock(m_cs); m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } The above fix looks good until you realize there's an even more subtle edge case. What happens if Shutdown gets called before OnHttpRequestComplete gets called back? The real world examples my team has are even more complex, and the edge cases are even harder to spot during the code review process. Common Mistake #2 - fixing deadlock issues by blindly exiting the lock, wait for the other thread to finish, then re-enter the lock - but without handling the case that the object just got updated by the other thread! Common Mistake #3 - Even though the objects are reference counted, the shutdown sequence "releases" it's pointer. But forgets to wait for the thread that is still running to release it's instance. As such, components are shutdown cleanly, then spurious or late callbacks are invoked on an object in an state not expecting any more calls. There are other edge cases, but the bottom line is this: Multithreaded programming is just plain hard, even for smart people. As I catch these mistakes, I spend time discussing the errors with each developer on developing a more appropriate fix. But I suspect they are often confused on how to solve each issue because of the enormous amount of legacy code that the "right" fix will involve touching. We're going to be shipping soon, and I'm sure the patches we're applying will hold for the upcoming release. Afterwards, we're going to have some time to improve the code base and refactor where needed. We won't have time to just re-write everything. And the majority of the code isn't all that bad. But I'm looking to refactor code such that threading issues can be avoided altogether. One approach I am considering is this. For each significant platform feature, have a dedicated single thread where all events and network callbacks get marshalled onto. Similar to COM apartment threading in Windows with use of a message loop. Long blocking operations could still get dispatched to a work pool thread, but the completion callback is invoked on on the component's thread. Components could possibly even share the same thread. Then all the class libraries running inside the thread can be written under the assumption of a single threaded world. Before I go down that path, I am also very interested if there are other standard techniques or design patterns for dealing with multithreaded issues. And I have to emphasize - something beyond a book that describes the basics of mutexes and semaphores. What do you think? I am also interested in any other approaches to take towards a refactoring process. Including any of the following: Literature or papers on design patterns around threads. Something beyond an introduction to mutexes and semaphores. We don't need massive parallelism either, just ways to design an object model so as to handle asynchronous events from other threads correctly. Ways to diagram the threading of various components, so that it will be easy to study and evolve solutions for. (That is, a UML equivalent for discussing threads across objects and classes) Educating your development team on the issues with multithreaded code. What would you do?

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  • How to deal with a ten days debugging session? [on hold]

    - by smonff
    Ten days ago, I fixed a bug on a large application and the hot fix has created a disappearing of some data from the user point of view. Data are not deleted, but have been set to hidden status. It could be possible to get the data back, but the thing seems to be hard: I've already spent 10 days to understand and reproduce the problem (mostly with complex SQL queries but sometimes it is necessary to update the database to test the application logic). Is 10 days a normal amount of time for these kind of problems? Should we keep on and retrieve the data or should we tell these users sorry for the loss, but your data have disappeared? Any advice on when to stop searching how to solve the issue?

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  • SQL Server 2008 R2 Reporting Services - The Word is But a Stage (T-SQL Tuesday #006)

    - by smisner
    Host Michael Coles (blog|twitter) has selected LOB data as the topic for this month's T-SQL Tuesday, so I'll take this opportunity to post an overview of reporting with spatial data types. As part of my work with SQL Server 2008 R2 Reporting Services, I've been exploring the use of spatial data types in the new map data region. You can create a map using any of the following data sources: Map Gallery - a set of Shapefiles for the United States only that ships with Reporting Services ESRI Shapefile - a .shp file conforming to the Environmental Systems Research Institute, Inc. (ESRI) shapefile spatial data format SQL Server spatial data - a query that includes SQLGeography or SQLGeometry data types Rob Farley (blog|twitter) points out today in his T-SQL Tuesday post that using the SQL geography field is a preferable alternative to ESRI shapefiles for storing spatial data in SQL Server. So how do you get spatial data? If you don't already have a GIS application in-house, you can find a variety of sources. Here are a few to get you started: US Census Bureau Website, http://www.census.gov/geo/www/tiger/ Global Administrative Areas Spatial Database, http://biogeo.berkeley.edu/gadm/ Digital Chart of the World Data Server, http://www.maproom.psu.edu/dcw/ In a recent post by Pinal Dave (blog|twitter), you can find a link to free shapefiles for download and a tutorial for using Shape2SQL, a free tool to convert shapefiles into SQL Server data. In my post today, I'll show you how to use combine spatial data that describes boundaries with spatial data in AdventureWorks2008R2 that identifies stores locations to embed a map in a report. Preparing the spatial data First, I downloaded Shapefile data for the administrative boundaries in France and unzipped the data to a local folder. Then I used Shape2SQL to upload the data into a SQL Server database called Spatial. I'm not sure of the reason why, but I had to uncheck the option to create a spatial index to upload the data. Otherwise, the upload appeared to run successfully, but no table appeared in my database. The zip file that I downloaded contained three files, but I didn't know what was in them until I used Shape2SQL to upload the data into tables. Then I found that FRA_adm0 contains spatial data for the country of France, FRA_adm1 contains spatial data for each region, and FRA_adm2 contains spatial data for each department (a subdivision of region). Next I prepared my SQL query containing sales data for fictional stores selling Adventure Works products in France. The Person.Address table in the AdventureWorks2008R2 database (which you can download from Codeplex) contains a SpatialLocation column which I joined - along with several other tables - to the Sales.Customer and Sales.Store tables. I'll be able to superimpose this data on a map to see where these stores are located. I included the SQL script for this query (as well as the spatial data for France) in the downloadable project that I created for this post. Step 1: Using the Map Wizard to Create a Map of France You can build a map without using the wizard, but I find it's rather useful in this case. Whether you use Business Intelligence Development Studio (BIDS) or Report Builder 3.0, the map wizard is the same. I used BIDS so that I could create a project that includes all the files related to this post. To get started, I added an empty report template to the project and named it France Stores. Then I opened the Toolbox window and dragged the Map item to the report body which starts the wizard. Here are the steps to perform to create a map of France: On the Choose a source of spatial data page of the wizard, select SQL Server spatial query, and click Next. On the Choose a dataset with SQL Server spatial data page, select Add a new dataset with SQL Server spatial data. On the Choose a connection to a SQL Server spatial data source page, select New. In the Data Source Properties dialog box, on the General page, add a connecton string like this (changing your server name if necessary): Data Source=(local);Initial Catalog=Spatial Click OK and then click Next. On the Design a query page, add a query for the country shape, like this: select * from fra_adm1 Click Next. The map wizard reads the spatial data and renders it for you on the Choose spatial data and map view options page, as shown below. You have the option to add a Bing Maps layer which shows surrounding countries. Depending on the type of Bing Maps layer that you choose to add (from Road, Aerial, or Hybrid) and the zoom percentage you select, you can view city names and roads and various boundaries. To keep from cluttering my map, I'm going to omit the Bing Maps layer in this example, but I do recommend that you experiment with this feature. It's a nice integration feature. Use the + or - button to rexize the map as needed. (I used the + button to increase the size of the map until its edges were just inside the boundaries of the visible map area (which is called the viewport). You can eliminate the color scale and distance scale boxes that appear in the map area later. Select the Embed map data in this report for faster rendering. The spatial data won't be changing, so there's no need to leave it in the database. However, it does increase the size of the RDL. Click Next. On the Choose map visualization page, select Basic Map. We'll add data for visualization later. For now, we have just the outline of France to serve as the foundation layer for our map. Click Next, and then click Finish. Now click the color scale box in the lower left corner of the map, and press the Delete key to remove it. Then repeat to remove the distance scale box in the lower right corner of the map. Step 2: Add a Map Layer to an Existing Map The map data region allows you to add multiple layers. Each layer is associated with a different data set. Thus far, we have the spatial data that defines the regional boundaries in the first map layer. Now I'll add in another layer for the store locations by following these steps: If the Map Layers windows is not visible, click the report body, and then click twice anywhere on the map data region to display it. Click on the New Layer Wizard button in the Map layers window. And then we start over again with the process by choosing a spatial data source. Select SQL Server spatial query, and click Next. Select Add a new dataset with SQL Server spatial data, and click Next. Click New, add a connection string to the AdventureWorks2008R2 database, and click Next. Add a query with spatial data (like the one I included in the downloadable project), and click Next. The location data now appears as another layer on top of the regional map created earlier. Use the + button to resize the map again to fill as much of the viewport as possible without cutting off edges of the map. You might need to drag the map within the viewport to center it properly. Select Embed map data in this report, and click Next. On the Choose map visualization page, select Basic Marker Map, and click Next. On the Choose color theme and data visualization page, in the Marker drop-down list, change the marker to diamond. There's no particular reason for a diamond; I think it stands out a little better than a circle on this map. Clear the Single color map checkbox as another way to distinguish the markers from the map. You can of course create an analytical map instead, which would change the size and/or color of the markers according to criteria that you specify, such as sales volume of each store, but I'll save that exploration for another post on another day. Click Finish and then click Preview to see the rendered report. Et voilà...c'est fini. Yes, it's a very simple map at this point, but there are many other things you can do to enhance the map. I'll create a series of posts to explore the possibilities. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Accessing SharePoint 2010 Data with REST/OData on Windows Phone 7

    - by Jan Tielens
    Consuming SharePoint 2010 data in Windows Phone 7 applications using the CTP version of the developer tools is quite a challenge. The issue is that the SharePoint 2010 data is not anonymously available; users need to authenticate to be able to access the data. When I first tried to access SharePoint 2010 data from my first Hello-World-type Windows Phone 7 application I thought “Hey, this should be easy!” because Windows Phone 7 development based on Silverlight and SharePoint 2010 has a Client Object Model for Silverlight. Unfortunately you can’t use the Client Object Model of SharePoint 2010 on the Windows Phone platform; there’s a reference to an assembly that’s not available (System.Windows.Browser). My second thought was “OK, no problem!” because SharePoint 2010 also exposes a REST/OData API to access SharePoint data. Using the REST API in SharePoint 2010 is as easy as making a web request for a URL (in which you specify the data you’d like to retrieve), e.g. http://yoursiteurl/_vti_bin/listdata.svc/Announcements. This is very easy to accomplish in a Silverlight application that’s running in the context of a page in a SharePoint site, because the credentials of the currently logged on user are automatically picked up and passed to the WCF service. But a Windows Phone application is of course running outside of the SharePoint site’s page, so the application should build credentials that have to be passed to SharePoint’s WCF service. This turns out to be a small challenge in Silverlight 3, the WebClient doesn’t support authentication; there is a Credentials property but when you set it and make the request you get a NotImplementedException exception. Probably this issued will be solved in the very near future, since Silverlight 4 does support authentication, and there’s already a WCF Data Services download that uses this new platform feature of Silverlight 4. So when Windows Phone platform switches to Silverlight 4, you can just use the WebClient to get the data. Even more, if the OData Client Library for Windows Phone 7 gets updated after that, things should get even easier! By the way: the things I’m writing in this paragraph are just assumptions that I make which make a lot of sense IMHO, I don’t have any info all of this will happen, but I really hope so. So are SharePoint developers out of the Windows Phone development game until they get this fixed? Well luckily not, when the HttpWebRequest class is being used instead, you can pass credentials! Using the HttpWebRequest class is slightly more complex than using the WebClient class, but the end result is that you have access to your precious SharePoint 2010 data. The following code snippet is getting all the announcements of an Annoucements list in a SharePoint site: HttpWebRequest webReq =     (HttpWebRequest)HttpWebRequest.Create("http://yoursite/_vti_bin/listdata.svc/Announcements");webReq.Credentials = new NetworkCredential("username", "password"); webReq.BeginGetResponse(    (result) => {        HttpWebRequest asyncReq = (HttpWebRequest)result.AsyncState;         XDocument xdoc = XDocument.Load(            ((HttpWebResponse)asyncReq.EndGetResponse(result)).GetResponseStream());         XNamespace ns = "http://www.w3.org/2005/Atom";        var items = from item in xdoc.Root.Elements(ns + "entry")                    select new { Title = item.Element(ns + "title").Value };         this.Dispatcher.BeginInvoke(() =>        {            foreach (var item in items)                MessageBox.Show(item.Title);        });    }, webReq); When you try this in a Windows Phone 7 application, make sure you add a reference to the System.Xml.Linq assembly, because the code uses Linq to XML to parse the resulting Atom feed, so the Title of every announcement is being displayed in a MessageBox. Check out my previous post if you’d like to see a more polished sample Windows Phone 7 application that displays SharePoint 2010 data.When you plan to use this technique, it’s of course a good idea to encapsulate the code doing the request, so it becomes really easy to get the data that you need. In the following code snippet you can find the GetAtomFeed method that gets the contents of any Atom feed, even if you need to authenticate to get access to the feed. delegate void GetAtomFeedCallback(Stream responseStream); public MainPage(){    InitializeComponent();     SupportedOrientations = SupportedPageOrientation.Portrait |         SupportedPageOrientation.Landscape;     string url = "http://yoursite/_vti_bin/listdata.svc/Announcements";    string username = "username";    string password = "password";    string domain = "";     GetAtomFeed(url, username, password, domain, (s) =>    {        XNamespace ns = "http://www.w3.org/2005/Atom";        XDocument xdoc = XDocument.Load(s);         var items = from item in xdoc.Root.Elements(ns + "entry")                    select new { Title = item.Element(ns + "title").Value };         this.Dispatcher.BeginInvoke(() =>        {            foreach (var item in items)            {                MessageBox.Show(item.Title);            }        });    });} private static void GetAtomFeed(string url, string username,     string password, string domain, GetAtomFeedCallback cb){    HttpWebRequest webReq = (HttpWebRequest)HttpWebRequest.Create(url);    webReq.Credentials = new NetworkCredential(username, password, domain);     webReq.BeginGetResponse(        (result) =>        {            HttpWebRequest asyncReq = (HttpWebRequest)result.AsyncState;            HttpWebResponse resp = (HttpWebResponse)asyncReq.EndGetResponse(result);            cb(resp.GetResponseStream());        }, webReq);}

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  • Would this be a good web application architecture?

    - by Gustav Bertram
    My problem Our MVC based framework does not allow us to cache only part of our output. Ideally we want to cahce static and semi-static bits, and run dynamic bits. In addition, we need to consider data caching that reacts to database changes. My idea The concept I came up with was to represent a page as a tree of XML fragment objects. (I say XML, but I mean XHTML). Some of the fragments are dynamic, and can pull their data directly from models or other sources, but most of the fragments are static scaffolding. If a subtree of fragments is completely static, then I imagine that they could unfold into pure XML that would then be cached as the text representation of their parent element. This process would ideally continue until we are left with a root element that contains all of the static XML, and has a couple of dynamic XML fragments that are resolved and attached to the relevant nodes of the XML tree just before the page is displayed. In addition to separating content into dynamic and static fragments, some fragments could be dynamic and cached. A simple expiry time which propagates up through the XML fragment tree would indicate that a specific fragment should periodically be refreshed. A newspaper section or front page does not need to be updated each second. Minutes or sometimes even longer is sufficient. Other fragments would be dynamic and uncached. Typically too many articles are viewed for them to be cached - the cache would overflow. Some individual articles may be cached if they are extremely popular. Functional notes The folding mechanism could be to be smart enough to judge when it would be more profitable to fold a dynamic cached fragment and propagate the expiry date to the parent fragment, or to keep it separate and simple attach to the XML tree when resolving the page. If some dynamic cached fragments are associated to database objects through mechanisms like a globally unique content id, then changes to the database could trigger changes to the output cache. If fragments store the identifiers of parent fragments, then they could trigger a refolding process that would then include the updated data. A set of pure XML with an ordered array of fragment objects (that each store the identifying information of the node to which they should be attached), can be resolved in a fairly simple way by walking the XML tree, and merging the data from the fragments. Because it is not necessary to parse and construct the entire tree in memory before attaching nodes, processing should be fairly fast. The identifiers of each fragment would be a combination of relevant identity data and the type of fragment object. Cached parent fragments would contain references to these identifiers, in order to then either pull them from the fragment cache, or to run their code. The controller's responsibility is reduced to making changes to the database, and telling the root XML fragment object to render itself. The Question My question has two parts: Is this a good design? Are there any obvious flaws I'm missing? Has somebody else thought of this before? References? Is there an existing alternative that I should consider? A cool templating engine maybe?

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  • MVC design in Cocoa - are all 3 always necessary? Also: naming conventions, where to put Controller

    - by Nektarios
    I'm new to MVC although I've read a lot of papers and information on the web. I know it's somewhat ambiguous and there are many different interpretations of MVC patterns.. but the differences seem somewhat minimal My main question is - are M, V, and C always going to be necessary to be doing this right? I haven't seen anyone address this in anything I've read. Examples (I'm working in Cocoa/Obj-c although that shouldn't much matter).. 1) If I have a simple image on my GUI, or a text entry field that is just for a user's convenience and isn't saved or modified, these both would be V (view) but there's no M (no data and no domain processing going on), and no C to bridge them. So I just have some aspects that are "V" - seems fine 2) I have 2 different and visible windows that each have a button on them labeled as "ACTIVATE FOO" - when a user clicks the button on either, both buttons press in and change to say "DEACTIVATE FOO" and a third window appears with label "FOO". Clicking the button again will change the button on both windows to "ACTIVATE FOO" and will remove the third "FOO" window. In this case, my V consists of the buttons on both windows, and I guess also the third window (maybe all 3 windows). I definitely have a C, my Controller object will know about these buttons and windows and will get their clicks and hold generic states regarding windows and buttons. However, whether I have 1 button or 10 button, my window is called "FOO" or my window is called "BAR", this doesn't matter. There's no domain knowledge or data here - just control of views. So in this example, I really have "V" and "C" but no "M" - is that ok? 3) Final example, which I am running in to the most. I have a text entry field as my View. When I enter text in this, say a number representing gravity, I keep it in a Model that may do things like compute physics of a ball while taking in to account my gravity parameter. Here I have a V and an M, but I don't understand why I would need to add a C - a controller would just accept the signals from the View and pass it along to the Model, and vice versa. Being as the C is just a pure passthrough, it's really "junk" code and isn't making things any more reusable in my opinion. In most situations, when something changes I will need to change the C and M both in nearly identical ways. I realize it's probably an MVC beginner's mistake to think most situations call for only V and M.. leads me in to next subject 4) In Cocoa / Xcode / IB, I guess my Controllers should always be an instantiated object in IB? That is, I lay all of my "V" components in IB, and for each collection of View objects (things that are related) I should have an instantiated Controller? And then perhaps my Models should NOT be found in IB, and instead only found as classes in Xcode that tie in with Controller code found there. Is this accurate? This could explain why you'd have a Controller that is not really adding value - because you are keeping consistent.. 5) What about naming these things - for my above example about FOO / BAR maybe something that ends in Controller would be the C, like FancyWindowOpeningController, etc? And for models - should I suffix them with like GravityBallPhysicsModel etc, or should I just name those whatever I like? I haven't seen enough code to know what's out there in the wild and I want to get on the right track early on Thank you in advance for setting me straight or letting me know I'm on the right track. I feel like I'm starting to get it and most of what I say here makes sense, but validation of my guessing would help me feel confident..

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  • Extract data from specific range of cells in multiple worksheet in multiple files.

    - by Michele
    Extract data from specific range of cells(always the same cells) in multiple worksheet in multiple files. 1 file=1 day. I have 6 technicians each day of the week, Monday thru Friday. So, 5 files with 6 worksheets. I have entered specific info in specific cells of every work sheet. The range is constant(the same address in EVERY worksheet in every file.) So, I need a formula to extract and calculate the data in the given range and dump it into another spreadsheet. I can forward an example a file if it will help anyone to answer my question. Or more explanation if necessary is available upon request. JUST PLEASE SOMEBODY HELP ME!!!!! Thank you all in advance. Regards, Michele

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  • How can I recover [data from] my failing USB key?

    - by moe37x3
    I have a Corsair Flash Voyager USB key, and it's almost completely failed. When I plug it into my [WinXP] computer, the OS mounts it and open up explorer to the drive's root directory. However, if I try to copy any data off, I get an error message saying that the device is not there. If I leave it plugged in, the OS seems to oscillate between seeing it and not seeing it, since the "Safely Remove Hardware" tray icon appears and disappears every few seconds. The damage was probably caused by my abuse, either from plugging it in with my keys hanging off of it or from losing the cap and keeping it in my pocket uncapped. Is there anything I can do to save the data from it or even rehabilitate the drive?

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  • Changing Word mail merge data source locations in bulk?

    - by Daft Viking
    I've just moved a number of Word mail merge files, and a number of Excel spreadsheets that are the data sources for the mail merges, from a Windows XP computer to a Windows 7 computer, and now all the paths for the merge sources are incorrect (used to be c:\documents and settings\user\my documents.... now c:\users\documents....). While I can correct the path of the data source in each file individually, I was hoping that there would be some way of updating the files in bulk, as there are a relatively large number of them. Word 2007 is what is being used, but the documents are all in the previous DOC format (not DOCX).

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  • Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder?

    - by Selin Peck
    Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder? I used to start office work by removing chrome User Data, replacing it with my own User Data copied from my external drive, saving the original User Data to other folder. Before leaving in the evening, I will take back my own User Data, and bring back the original User Data where it is originally saved. Is this process advisable? Would I be safe this way or if not, where else does chrome save data outside of User Data folder in AppData? Also, how is the process in Mozilla Firefox?

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  • How do I populate multiple records of data into a PDF form like a mail-merge?

    - by user38801
    I have Acrobat Pro, and I have a PDF with a form on it. Assuming the fields in the form correspond to a data source (like rows in an RDBMS table or xml file), I want to then print multiple copies of the PDF file, with each copy having the values of a different row in the data source. It is preferable to directly interface with an actual database, rather than having to save an XML file every time I do this. If this involves programming that's cool too, I only posted here because the question didn't seem appropriate for StackOverflow. Thanks!

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  • Ways to improve completeness of files for data recovery and scanning?

    - by SteveO
    I am using R-studio for data recovery on one of my ntfs partition. There is a pdf file about 16MB, but the software can only recover 15MB of it. So I am thinking about what ways can be used to improve the quality of scanning and recovery by the software? I am looking around its preferences. I am not quite sure whether there are some adjustable parameters for scanning and recovery which can be fine-tuned to improve the quality? R-studio has a free demo version, for which scanning is free,but recovery isn't. It is downloadable from http://www.data-recovery-software.net/Data_Recovery_Download.shtml Its manual is here http://www.r-tt.com/downloads/Recovery_Manual.pdf. I have tried my best to search for answers in the manual, but failed to find one. Their technical support is not as good as their software, and helpless usually in my opinion. Thanks!

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  • Looking for design/architecture suggestions for a simple HTML game.

    - by z-boss
    Imagine that HTML page is a game surface (see picture). User can have n number of boards (blue divs) on his page. Each board can be moved, re-sized, relabeled, created new and removed. Inside each board there are m number of figures (purple divs). Each of these user can move inside the board or to another board, re-size, change color and label, delete, add new. The goal of the game is not important, but let's say it is to rearrange figures in a certain way so that they disappear. But the goal of the programmer is to save the whole game surface in the database for every user of the site, and to load it later when he returns. So, how do I go about data exchange between client and the database? I'll give my idea in one of the answers.

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  • What resources will help me understand the fundamentals of Relational Database Design.

    - by Rachel
    This are few of the fundamental database questions which has always given me trouble. I have tried using google and wiki but I somehow I miss out on understanding the functionality rather than terminology. If possible would really appreciate if someone can share more insights on this questions using some visual representative examples. What is a key? A candidate key? A primary key? An alternate key? A foreign key? What is an index and how does it help your database? What are the data types available and when to use which ones?

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  • Database table design vs. ease of use.

    - by Gastoni
    I have a table with 3 fields: color, fruit, date. I can pick 1 fruit and 1 color, but I can do this only once each day. examples: red, apple, monday red, mango, monday blue, apple, monday blue, mango, monday red, apple, tuesday The two ways in which I could build the table are: 1.- To have color, fruit and date be a composite primary key (PK). This makes it easy to insert data into the table because all the validation needed is done by the database. PK color PK fruit PK date 2.- Have and id column set as PK and then all the other fields. Many say thats the way it should be, because composite PKs are evil. For example, CakePHP does no support them. PK id color fruit date Both have advantages. Which would be the 'better' approach?

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  • Using Microsoft's Chart Controls In An ASP.NET Application: Serializing Chart Data

    In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the Getting Started article rendered a column chart with seven columns whose labels and values were defined statically in the <asp:Series> tag's <Points> collection. Given this functionality, it should come as no surprise that the Microsoft Chart Controls also support serialization. Serialization is the process of persisting the state of a control or an object to some other medium, such as to disk. Deserialization is the inverse process, and involves taking the persisted data and recreating the control or object. With just a few lines of code you can persist the appearance settings, the data, or both to a file on disk or to any stream. Likewise, it takes just a few lines of codes to reconstitute a chart from the persisted information. This article shows how to use the Microsoft Chart Control's serialization functionality by examining a demo application that allows users to create custom charts, specifying the data to plot and some appearance-related settings. The user can then save a "snapshot" of this chart, which persists its appearance and data to a record in a database. From another page, users can view these saved chart snapshots. Read on to learn more! Read More >

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  • SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

    - by pinaldave
    This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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  • Join our webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate

    - by Irem Radzik
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";} Data integration team has organized a series of webcasts for this summer. We are kicking it off this Thursday June 30th at 10am PT with a product update webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate. In this webcast you will hear from product management about the new patch updates to both GoldenGate 11g R1 and ODI 11gR1. Jeff Pollock, Sr. Director of Product Management for ODI will talk about the new features in Oracle Data Integrator 11.1.1.5, including the data lineage integration with OBI EE, enhanced web services to support flexible architectures as well as capabilities for efficient object execution such as Load Plans. Jeff will discuss support for complex files and performance enhancements. Chris McAllister, Sr. Director of Product Management for Oracle GoldenGate will cover the new features of Oracle GoldenGate 11.1.1.1 such as increased data security by supporting Oracle Database Advanced Security option, deeper integration with Oracle Database, and the expanded list of heterogeneous databases GoldenGate supports . Chris will also talk about the new Oracle GoldenGate 11gR1 release for HP NonStop platform and will provide information on our strategic direction for product development. Join us this Thursday at 10am PT/ 1pm ET to hear directly from Data Integration Product Management . You can register here for the June 30th webcast as well as for the upcoming ones in our summer webcast series.

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  • Oracle Database Security Protecting the Oracle IRM Schema

    - by Simon Thorpe
    Acquiring the Information Rights Management technology in 2006 was part of Oracle's strategic security vision and IRM compliments nicely the overall Oracle security set of solutions. A year ago I spoke about how Oracle has solutions that can help companies protect information throughout its entire life cycle. With our acquisition of Sun this set of solutions has solidified and has even extended down to the operating system and hardware level. Oracle can now offer customers technology that protects their data from the disk, through the database to documents on the desktop! With the recent release of Oracle IRM 11g I was tasked to configure demonstration and evaluation environments and I thought it would make a nice story to leverage some of the security features in the latest release of the Oracle Database. After building these environments I thought I would put together a simple video demonstrating how both Database Advanced Security and Information Rights Management combined can provide a very secure platform for protecting your information. Have a look at the following which highlights these database security options.Transparent Data Encryption protecting the communication from the Oracle IRM server to the Database server. Encryption techniques provide confidentiality and integrity of the data passing to and from the IRM service on the back end. Transparent Data Encryption protecting the Oracle IRM database schema. Encryption is used to provide confidentiality of the IRM data whilst it resides at rest in the database table space. Database Vault is used to ensure only the Oracle IRM service has access to query and update the information that resides in the database. This is an excellent method of ensuring that database administrators cannot look at or make changes to the Oracle IRM database whilst retaining their ability to administrate the database. The last thing you want after deploying an IRM solution is for a curious or unhappy DBA to run a query that grants them rights to your company financial data or documents pertaining to a merger or acquisition.

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  • Methodology behind fetching large XML data sets in pieces

    - by Jerry Dodge
    I am working on an HTTP Server in Delphi which simply sends back a custom XML dataset. I am not following any type of standard formatting, such as SOAP. I have the system working seamlessly, except one small flaw: When I have a very large dataset to send back to the client, it might take up to 2 minutes for all the data to be transferred. The HTTP Server I'm building is essentially an XML Data based API around a database, implementing the common business rule - therefore, the requests are specific to the data behind the system. When, for example, I fetch a large set of product data, I would like to break this down and send it back piece by piece. However, a single HTTP request calls for a single response. I can't necessarily keep feeding the client with multiple different XML packets unless the client explicitly requests it. I don't have any session management, but rather an API Key. I know if I had sessions, I could keep-alive a dataset temporarily for a client, and they could request bits and pieces of it. However, without session management, I would have to execute the SQL query multiple times (for each chunk of data), and in the mean-time, if that data changes, the "pages" might get messed up, therefore causing items to show on the wrong pages, after navigating to a different page. So how is this commonly handled? What's the methodology behind breaking down a large XML dataset into chunks to save the load?

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