Search Results

Search found 18534 results on 742 pages for 'dave long'.

Page 438/742 | < Previous Page | 434 435 436 437 438 439 440 441 442 443 444 445  | Next Page >

  • Android daemon process

    - by J Andy
    Is it possible (without violating any licenses) to write a native C/C++ application on top of the Android OS and make it run as a daemon process? There are already several daemon process' running which one can see with the 'ps' command, the legal part concerns me the most. And also the lack of documentation on how to exactly do this. For the writing part, I guess one could use basic Linux programming concepts, since Android supports at least to some level the standard Posix API. To make it run as the phone boots, some modifications is of course required in init as well. I have no plans to have this app in the Android Market, so installing it manually to the phone is not a problem. As long as it does not require re-compiling the whole OS or kernel. I really appreciate all info on this topic, since there's isn't much available. Thanks.

    Read the article

  • Accessing Google Spreadsheets with C# using Google Data API fails with Mono

    - by Maurits Rijk
    I'm trying to access my Google spreadsheets using the GData API. I have followed the example which looks like: var service = new SpreadsheetsService("myTest"); service.setUserCredentials(username, password); var query = new SpreadsheetQuery(); var feed = service.Query(query); This should return a feed with a list of spreadsheets. However this fails with: Google.GData.Client.GDataRequestException: Execution of request failed: http://spreadsheets.google.com/feeds/spreadsheets/private/full --- System.Net.WebException: The remote server returned an error: (404) Not Found. When I try the above link directly in my browser I'm able to download the feed, as long as I'm logged in into my Google account. Some further information: I'm not behind a firewall I have checked my username (maurits.rijk at gmail.com) and password several times I am using Mandriva in VirtualBox on a MacBook All my code is compiled with Mono I tried the same functionality in Java on OS-X. That code runs as expected.

    Read the article

  • MDI WinForm application and duplicate child form memory leak

    - by Steve
    This is a WinForm MDI application problem (.net framework 3.0). It will be described in C#. Sorry it is a bit long because I try to make things as clear as possible. I have a MDI application. At some point I find that one MDI child form is never released. There is a menu that creates the MDI child form and show it. When the MDI child form is closed, it is supposed to be destroyed and the memory taken by it should be given back to .net. But to my surprise, this is not true. All the MDI child form instances are kept in memory. This is obviously a "memory leak". Well, it is not a real leak in .net. It is just that I think the closed form should be dead but somehow there is at least one unknown reference from outside world that still connect with the closed form. I read some articles on the Web. Some says that when the MDI child form is closing, I should unwire all the event handlers, otherwise some event handlers may keep my form alive. Some says that DataBindings should be cleaned before the form is closing otherwise the DataBindings will add references to some global Hashtable and thus keep my form alive. My form contains quite a lot things. Many event handlers and many DataBindings and many BindingSources and few suspected controls containing user control and HelpProvider. I create a big method that unwires all the event handlers from all the relevant controls, clear all the DataBindings and DataSources. The HelpProvider and user controls are disposed carefully. At the end, I find that, I don't have to clear DataBindings and DataSources. Event handlers are definitely causing the problem. And MDI form structure also contributes to something. During my experiments, I find that, if you create a MDI child form, even if you close it, there will still be one instance in the memory. The reference is from PropertyStore of the main form. This means, unless the main form is closed (application ends), there will always be one instance of MDI child form in the memory. The good news is that, no matter how many times you open and close the child form, there will be only one instance, not a big "leak". When it comes to event handlers, things become more tricky. I have to address that, all the event handlers on my form are anonymous event handlers. Here is an example code: //On MDI child form's design code... Button btnSave = new Button(); btnSave.Click += new System.EventHandler(btnSave_Click); Where btnSave_Click is also a method in MDI child form. The above is always the case for various controls and various types of event. To me, this is a bi-directional circular reference. btnSave keeps a reference of MDI child form via the event handler. MDI child form keeps a reference of btnSave instance. To me again, such bi-directional circular reference should not cause any problem for .net's garbage collector. This means that I do not have to explicitly unwire the event when the form is being disposed: btnSave.Click -= btnSave_Click; But the truth is not so. For some event handlers, they are safe. Ignoring them do not cause any duplicate instance. For some other event handlers, they will cause one instance remaining in the memory (similar effect as the MDI form structure, but this time caused by the hanging event handlers). For some other event handlers, they will cause every instance opened in the memory. I am totally confused about the differences between these three types of event handlers. The controls are created in the same way and the event is attached in the same way. What is the difference? (Don't tell me it is the event handle methods that make difference.) Anyone has experience of this wired scenario and has an answer for me? Thanks a lot. So now, for safety issue, I will have to unwire all the event handlers when the form is being disposed. That will be a long list of similar code for each control. Is there a general way of removing events from controls in recursive way using reflection? What about performance issue? That's the end of my story and I am still in the middle of my problem. For any help, I thank you.

    Read the article

  • Cross-platform embedded database/key-value store for C#

    - by Arne Claassen
    I'm looking for a fast, embeddable key/value store with cursor semantics over key collections (or a simple embeddable DB) that I can use in .NET and mono. Need it to be open-source, would prefer an MIT or Apache style license over a GPL license. Not opposed to a library that needs bindings to be written, as long as binaries are available for both windows and linux. Options considered: SQLite - has bindings and native implementation, but single-threaded and not all that fast Embedded InnoDB - no .NET bindings i can find and it's GPLv2 Berkley DB - no .NET bindings i can find Tokyo Cabinet - no .NET bindings i can find and problematic to build on windows MadCow Memory-mapped data structures - GPLv2 Is there an option better than the above that i'm missing, or bindings for the above i don't know about?

    Read the article

  • TypeLoadException at startup of WCF

    - by Kelly
    I get the following error long before I hit the breakpoint at Main(). System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. at System.Reflection.Module._GetTypesInternal(StackCrawlMark& stackMark) at System.Reflection.Assembly.GetTypes() at Microsoft.Tools.SvcHost.ServiceHostHelper.LoadServiceAssembly(String svcAssemblyPath) There is a suggestion that it might be a configuration error, but I don't see it when comparing to a similar, working example. How do I "Retrieve the LoaderExceptions property" when it happens this early? Thanks!

    Read the article

  • Error reading in date using Zoo in R

    - by SASnewby
    I am trying to use the Zoo package to read in daily observations which do not occur on each day. The date format looks like this, and it is in the first column of dataset: 25-May-07 The command I use is: z <- read.zoo("multiplier7.csv", sep = ";", header = TRUE, format="%d-%b-%y") I get this error: Error in strptime(x, format, tz = "GMT") : input string is too long First question is: 1. Is Zoo the right package to use if I want to use lm regression with a spline time dummy? The bs command does not work because I need to convert it into a time series. 2. Why is this error occurring and how to fix?

    Read the article

  • jQuery: Dynamic image handling (waiting for load)

    - by dclowd9901
    I'm trying to write a plugin that has a built in function to wait until all images that are on the page to be loaded before it executes itself. $(window).load() only works if it's the initial load of the page, but if someone wants to pull down some HTML through AJAX that contains images, it doesn't work. Is there any good way of doing this AND implementing it so that it can be self-contained in the plug-in? I've tried looping over $('img').complete, and I know that doesn't work (the images never load, and the browser crashes under a "script takes too long to complete" bug). For an example of what I'm trying to do, visit the page I'm looking to house the plugin at: http://www.simplesli.de If you go to the "more uses" section (click it on the nav bar), you'll see that the image slideshow won't load properly. I know the current code doesn't work, but it's just holding place until I figure something out.

    Read the article

  • Running each JUnit test in a separate JVM in Eclipse?

    - by HenryR
    I have a project with nearly 500 individual tests in around 200 test classes. Some of these tests don't do a great job of tearing down their own state after they're finished, and in Eclipse this results in some tests failing. The tests all pass when running the test suite from the command line via Ant. Can I enable 'test isolation' somehow in Eclipse? I don't mind if it takes longer to run. Long term, I will clean up the misbehaving tests, but in the short term I'd like to get the tests working.

    Read the article

  • to_date in MS SQL Server 2005

    - by Chin
    Does any one know how I would have to change the following to work with ms sql? WHERE registrationDate between to_date ('2003/01/01', 'yyyy/mm/dd') AND to_date ('2003/12/31', 'yyyy/mm/dd'); What I have read implies I would have to construct it using DATEPART() which could become very long winded. Especially when the goal would be to compare on dates which I receive in the following format "2003-12-30 10:07:42". It would be nice to pass them off to the database as is. Any pointers appreciated.

    Read the article

  • WPF DataGrid: How to reset column width when applying new ItemsSource

    - by paul
    I am using a DataGrid to display details of an item selected in a ListBox. The DataGrid has 3 columns set to Width="Auto". As different items in the ListBox are selected, the width of the columns in the DataGrid increase as needed in order to display the text. What I want is that the column widths also decrease when the extra width is not needed. An example. Column 1 normally contains a percent value. However, in some cases it contains a long error message which causes column 1 to widen and push columns 2 & 3 off the screen. When I switch to an item containing normal values, I want column 1 to regain its' normal width and for columns 2 & 3 to be visible again. What can I do to force the column widths to take the minimum size?

    Read the article

  • DAL without web2py

    - by Jay
    I am using web2py to power my web site. I decided to use the web2py DAL for a long running program that runs behind the site. This program does not seem to update its data or the database (sometimes). from gluon.sql import * from gluon.sql import SQLDB from locdb import * # contains # db = SQLDB("mysql://user/pw@localhost/mydb", pool_size=10) # db.define_table('orders', Field('status', 'integer'), Field('item', 'string'), # migrate='orders.table') orderid = 20 # there is row with id == 20 in table orders #when I do db(db.orders.id==orderid).update(status=6703) db.commit() It does not update the database, and a select on orders with this id, shows the correct data. In some circumstances a "db.rollback()" after a commit seems to help. Very strange to say the least. Have you seen this, more importantly do you know the solution? Jay

    Read the article

  • Laissez les bon temps rouler! (Microsoft BI Conference 2010)

    - by smisner
    "Laissez les bons temps rouler" is a Cajun phrase that I heard frequently when I lived in New Orleans in the mid-1990s. It means "Let the good times roll!" and encapsulates a feeling of happy expectation. As I met with many of my peers and new acquaintances at the Microsoft BI Conference last week, this phrase kept running through my mind as people spoke about their plans in their respective businesses, the benefits and opportunities that the recent releases in the BI stack are providing, and their expectations about the future of the BI stack. Notwithstanding some jabs here and there to point out the platform is neither perfect now nor will be anytime soon (along with admissions that the competitors are also not perfect), and notwithstanding several missteps by the event organizers (which I don't care to enumerate), the overarching mood at the conference was positive. It was a refreshing change from the doom and gloom hovering over several conferences that I attended in 2009. Although many people expect economic hardships to continue over the coming year or so, everyone I know in the BI field is busier than ever and expects to stay busy for quite a while. Self-Service BI Self-service was definitely a theme of the BI conference. In the keynote, Ted Kummert opened with a look back to a fairy tale vision of self-service BI that he told in 2008. At that time, the fairy tale future was a time when "every end user was able to use BI technologies within their job in order to move forward more effectively" and transitioned to the present time in which SQL Server 2008 R2, Office 2010, and SharePoint 2010 are available to deliver managed self-service BI. This set of technologies is presumably poised to address the needs of the 80% of users that Kummert said do not use BI today. He proceeded to outline a series of activities that users ought to be able to do themselves--from simple changes to a report like formatting or an addtional data visualization to integration of an additional data source. The keynote then continued with a series of demonstrations of both current and future technology in support of self-service BI. Some highlights that interested me: PowerPivot, of course, is the flagship product for self-service BI in the Microsoft BI stack. In the TechEd keynote, which was open to the BI conference attendees, Amir Netz (twitter) impressed the audience by demonstrating interactivity with a workbook containing 100 million rows. He upped the ante at the BI keynote with his demonstration of a future-state PowerPivot workbook containing over 2 billion records. It's important to note that this volume of data is being processed by a server engine, and not in the PowerPivot client engine. (Yes, I think it's impressive, but none of my clients are typically wrangling with 2 billion records at a time. Maybe they're thinking too small. This ability to work quickly with large data sets has greater implications for BI solutions than for self-service BI, in my opinion.) Amir also demonstrated KPIs for the future PowerPivot, which appeared to be easier to implement than in any other Microsoft product that supports KPIs, apart from simple KPIs in SharePoint. (My initial reaction is that we have one more place to build KPIs. Great. It's confusing enough. I haven't seen how well those KPIs integrate with other BI tools, which will be important for adoption.) One more PowerPivot feature that Amir showed was a graphical display of the lineage for calculations. (This is hugely practical, especially if you build up calculations incrementally. You can more easily follow the logic from calculation to calculation. Furthermore, if you need to make a change to one calculation, you can assess the impact on other calculations.) Another product demonstration will be available within the next 30 days--Pivot for Reporting Services. If you haven't seen this technology yet, check it out at www.getpivot.com. (It definitely has a wow factor, but I'm skeptical about its practicality. However, I'm looking forward to trying it out with data that I understand.) Michael Tejedor (twitter) demonstrated a feature that I think is really interesting and not emphasized nearly enough--overshadowed by PowerPivot, no doubt. That feature is the Microsoft Business Intelligence Indexing Connector, which enables search of the content of Excel workbooks and Reporting Services reports. (This capability existed in MOSS 2007, but was more cumbersome to implement. The search results in SharePoint 2010 are not only cooler, but more useful by describing whether the content is found in a table or a chart, for example.) This may yet be the dawning of the age of self-service BI - a phrase I've heard repeated from time to time over the last decade - but I think BI professionals are likely to stay busy for a long while, and need not start looking for a new line of work. Kummert repeatedly referenced strategic BI solutions in contrast to self-service BI to emphasize that self-service BI is not a replacement for the services that BI professionals provide. After all, self-service BI does not appear magically on user desktops (or whatever device they want to use). A supporting infrastructure is necessary, and grows in complexity in proportion to the need to simplify BI for users. It's one thing to hear the party line touted by Microsoft employees at the BI keynote, but it's another to hear from the people who are responsible for implementing and supporting it within an organization. Rob Collie (blog | twitter), Kasper de Jonge (blog | twitter), Vidas Matelis (site | twitter), and I were invited to join Andrew Brust (blog | twitter) as he led a Birds of a Feather session at TechEd entitled "PowerPivot: Is It the BI Deal-Changer for Developers and IT Pros?" I would single out the prevailing concern in this session as the issue of control. On one side of this issue were those who were concerned that they would lose control once PowerPivot is implemented. On the other side were those who believed that data should be freely accessible to users in PowerPivot, and even acknowledgment that users would get the data they want even if it meant they would have to manually enter into a workbook to have it ready for analysis. For another viewpoint on how PowerPivot played out at the conference, see Rob Collie's observations. Collaborative BI I have been intrigued by the notion of collaborative BI for a very long time. Before I discovered BI, I was a Lotus Notes developer and later a manager of developers, working in a software company that enabled collaboration in the legal industry. Not only did I help create collaborative systems for our clients, I created a complete project management from the ground up to collaboratively manage our custom development work. In that case, collaboration involved my team, my client contacts, and me. I was also able to produce my own BI from that system as well, but didn't know that's what I was doing at the time. Only in recent years has SharePoint begun to catch up with the capabilities that I had with Lotus Notes more than a decade ago. Eventually, I had the opportunity at that job to formally investigate BI as another product offering for our software, and the rest - as they say - is history. I built my first data warehouse with Scott Cameron (who has also ventured into the authoring world by writing Analysis Services 2008 Step by Step and was at the BI Conference last week where I got to reminisce with him for a bit) and that began a career that I never imagined at the time. Fast forward to 2010, and I'm still lauding the virtues of collaborative BI, if only the tools will catch up to my vision! Thus, I was anxious to see what Donald Farmer (blog | twitter) and Rita Sallam of Gartner had to say on the subject in their session "Collaborative Decision Making." As I suspected, the tools aren't quite there yet, but the vendors are moving in the right direction. One thing I liked about this session was a non-Microsoft perspective of the state of the industry with regard to collaborative BI. In addition, this session included a better demonstration of SharePoint collaborative BI capabilities than appeared in the BI keynote. Check out the video in the link to the session to see the demonstration. One of the use cases that was demonstrated was linking from information to a person, because, as Donald put it, "People don't trust data, they trust people." The Microsoft BI Stack in General A question I hear all the time from students when I'm teaching is how to know what tools to use when there is overlap between products in the BI stack. I've never taken the time to codify my thoughts on the subject, but saw that my friend Dan Bulos provided good insight on this topic from a variety of perspectives in his session, "So Many BI Tools, So Little Time." I thought one of his best points was that ideally you should be able to design in your tool of choice, and then deploy to your tool of choice. Unfortunately, the ideal is yet to become real across the platform. The closest we come is with the RDL in Reporting Services which can be produced from two different tools (Report Builder or Business Intelligence Development Studio's Report Designer), manually, or by a third-party or custom application. I have touted the idea for years (and publicly said so about 5 years ago) that eventually more products would be RDL producers or consumers, but we aren't there yet. Maybe in another 5 years. Another interesting session that covered the BI stack against a backdrop of competitive products was delivered by Andrew Brust. Andrew did a marvelous job of consolidating a lot of information in a way that clearly communicated how various vendors' offerings compared to the Microsoft BI stack. He also made a particularly compelling argument about how the existence of an ecosystem around the Microsoft BI stack provided innovation and opportunities lacking for other vendors. Check out his presentation, "How Does the Microsoft BI Stack...Stack Up?" Expo Hall I had planned to spend more time in the Expo Hall to see who was doing new things with the BI stack, but didn't manage to get very far. Each time I set out on an exploratory mission, I got caught up in some fascinating conversations with one or more of my peers. I find interacting with people that I meet at conferences just as important as attending sessions to learn something new. There were a couple of items that really caught me eye, however, that I'll share here. Pragmatic Works. Whether you develop SSIS packages, build SSAS cubes, or author SSRS reports (or all of the above), you really must take a look at BI Documenter. Brian Knight (twitter) walked me through the key features, and I must say I was impressed. Once you've seen what this product can do, you won't want to document your BI projects any other way. You can download a free single-user database edition, or choose from more feature-rich standard or professional editions. Microsoft Press ebooks. I also stopped by the O'Reilly Media booth to meet some folks that one of my acquisitions editors at Microsoft Press recommended. In case you haven't heard, Microsoft Press has partnered with O'Reilly Media for distribution and publishing. Apart from my interest in learning more about O'Reilly Media as an author, an advertisement in their booth caught me eye which I think is a really great move. When you buy Microsoft Press ebooks through the O'Reilly web site, you can receive it in any (or all) of the following formats where possible: PDF, epub, .mobi for Kindle and .apk for Android. You also have lifetime DRM-free access to the ebooks. As someone who is an avid collector of books, I fnd myself running out of room for storage. In addition, I travel a lot, and it's hard to lug my reference library with me. Today's e-reader options make the move to digital books a more viable way to grow my library. Having a variety of formats means I am not limited to a single device, and lifetime access means I don't have to worry about keeping track of where I've stored my files. Because the e-books are DRM-free, I can copy and paste when I'm compiling notes, and I can print pages when necessary. That's a winning combination in my mind! Overall, I was pleased with the BI conference. There were many more sessions that I couldn't attend, either because the room was full when I got there or there were multiple sessions running concurrently that I wanted to see. Fortunately, many of the sessions are accessible for viewing online at http://www.msteched.com/2010/NorthAmerica along with the TechEd sessions. You can spot the BI sessions by the yellow skyline on the title slide of the presentation as shown below. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

    Read the article

  • Doxygen C++ comment string parser in python?

    - by Sebastian
    Does anybody know of a python module to parse a doxygen style C++ comment string? I mean a string like this (simple example): /** * A constructor. * A more elaborate description of the constructor. * @param param1 test1 * @param param2 test2 */ and I would like to extract the brief, the long description, the parameters, the return value etc. I'm currently doing this using string methods and regular expressions but my solution is not very robust. Alternatively does anybody know an easy to use parser lib that I can set up quickly? Thanks in advance

    Read the article

  • WPF ListView column auto sizing

    - by Diego Mijelshon
    Let's say I have the following ListView: <ListView ScrollViewer.VerticalScrollBarVisibility="Auto"> <ListView.View> <GridView> <GridViewColumn Header="Something" DisplayMemberBinding="{Binding Path=ShortText}" /> <GridViewColumn Header="Description" DisplayMemberBinding="{Binding Path=VeryLongTextWithCRs}" /> <GridViewColumn Header="Something Else" DisplayMemberBinding="{Binding Path=AnotherShortText}" /> </GridView> </ListView.View> </ListView> I'd like the short text columns to always fit in the screen, and the long text column to use the remaining space, word-wrapping if necessary. Is that possible?

    Read the article

  • Best way to detect integer overflow in C/C++

    - by Chris Johnson
    I was writing a program in C++ to find all solutions of a^b = c (a to the power of b), where a, b and c together use all the digits 0-9 exactly once. The program looped over values of a and b, and ran a digit-counting routine each time on a, b and a^b to check if the digits condition was satisfied. However, spurious solutions can be generated when a^b overflows the integer limit. I ended up checking for this using code like: unsigned long b, c, c_test; ... c_test=c*b; // Possible overflow if (c_test/b != c) {/* There has been an overflow*/} else c=c_test; // No overflow Is there a better way of testing for overflow? I know that some chips have an internal flag that is set when overflow occurs, but I've never seen it accessed through C or C++.

    Read the article

  • FormsAuthentication.SignOut() does not log the user out.

    - by Jason
    Smashed my head against this a bit too long. How do I prevent a user from browsing a site's pages after they have been logged out using FormsAuthentication.SignOut? I would expect this to do it: FormsAuthentication.SignOut(); Session.Abandon(); FormsAuthentication.RedirectToLoginPage(); But it doesn't. If I type in a URL directly, I can still browse to the page. I haven't used roll-your-own security in a while so I forget why this doesn't work.

    Read the article

  • 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

    Read the article

  • How can I stop SQL Server Reporting Services 2008 going to sleep?

    - by Nick
    I have SSRS 2008 set-up on a server. All works fine except that if left inactive for a length of time the next time a request is made to the server it takes a long time for it to service it. I think this is to do with the worker process being shutdown after being idle for a certain length of time. However, as SSRS 2008 isn't managed through IIS I can't find any settings that I can adjust to stop this from happening. In IIS I'd go to the Performance tab of the Application Pool Properties and choose not to shutdown the worker process. How can I do this for SSRS 2008?

    Read the article

  • Firefox jQuery Drag and Drop File Upload together with PHP

    - by tonsils
    Hi, Hoping to get some assistance but I am after a jQuery/PHP means of allowing a user to drag and drop files and then via PHP, upload one or more files to a specific directory on a Linux box. I only have Firefox 3.6 as my base browser but can also move to FFox if need be. Cann use any HTML5 features as long as I'm using Firefox 3.6 Can someone possibly point me to any examples/sites where this process is demonstrated? I have had a look at http://www.plupload.com/index.php but this does not work in IE6. As mentioned, would like it to work in FFox only. Thanks.

    Read the article

  • Best Practices for persisting iPod Playlist (MPMediaItemCollection) across sessions

    - by coneybeare
    When using in-app audio in the iPhone SDK, it is possible to allow users to select a list from their ipod library and create an in-app local playlist. If I want to persist this choice, it is easy to serialize the data and write to file, then recover. Just vanilla like this, however, leads me to think there is going to be something wrong. For example, what if the user syncs and removes sounds? I can loop across them all and query the iPod DB at setup time, but with lists that could be 50,000 long, this could take some time. How are other people doing this and what are some gotchas that I haven't though about?

    Read the article

  • Translate query to NHibernate

    - by Rob Walker
    I am trying to learn NHibernate, and am having difficulty translating a SQL query into one using the criteria API. The data model has tables: Part (Id, Name, ...), Order (Id, PartId, Qty), Shipment (Id, PartId, Qty) For all the parts I want to find the total quantity ordered and the total quantity shipped. In SQL I have: select shipment.part_id, sum(shipment.quantity), sum(order.quantity) from shipment cross join order on order.part_id = shipment.part_id group by shipment.part_id Alternatively: select id, (select sum(quantity) from shipment where part_id = part.id), (select sum(quantity) from order where part_id = part.id) from part But the latter query takes over twice as long to execute. Any suggestions on how to create these queries in (fluent) NHibernate? I have all the tables mapped and loading/saving/etc the entities works fine.

    Read the article

  • How to (pre)start xamlx workflow service

    - by rwwilden
    Related to this question. I have a xamlx workflow service that loads part of its definition from a database when it runs (using ActivityXamlServices.Load). Reason for this is that I need versioning, see the related question. I'll use WCF routing to direct calls to the right service. The part that I load dynamically contains a Receive activity. However, this activity is 'invisible' as long as the workflow doesn't start because the part of the workflow I load from the database is only loaded when the workflow starts. So from the outside it appears as if there is no Receive activity in the workflow. Apart from not being able to generate a contract for the workflow service, I can't call the service either. My first attempt was to do a soap call with the right contract on the workflow service. However, the runtime doesn't automagically activate my workflow in that case. So the question is, how do I start a workflow that is hosted inside IIS? Regards, Ronald

    Read the article

  • Documenting applications - automation / semi-automation for screenshots?

    - by bguiz
    For me one of the biggest bores of being a developer is writing user documentation. (I am referring to the stuff that gets exported into PDF files files that ship with the product, not comments in code here). The task off adding or updating new bits of text to the existing documentation is OK. However having to take screenshots of select screens can be quite a tedious process. Is there a way to automate or even semi-automate the process of taking screenshots? The main requirement is the ability to crop images such that they contain only the window, including window manager areas (such as the title bar). The secondary requirement is that any format is OK, so long as it can be exported to PDF. EDIT: Any more biters?

    Read the article

  • What exactly is the "Multi-threaded Debug DLL" Runtime Library option doing in VS 2008?

    - by GregH
    I have a solution in VS 2008 that creates a DLL. I then use that DLL in another application. If I go in to the DLL projects property pages and change the following configuration for a DEBUG build then the built dll no long provides the desired functionality. If I change it back and rebuild the DLL, then the DLL does provide the correct functionality: Property Pages = Configuration Properties = C/C++ = Code Generation = Runtime Library If set to "Multi-threaded Debug DLL (/MDd)" then everything works as it should. I get the correct functionality from the DLL If set to "Multi-threaded DLL (/MD)" then the DLL does not function properly...no runtime errors or anything, it just doesn't work (The DLL is supposed to plot some lines on a map but does not in this mode). So the question is, why does using the /MDd flag result in correction functionality of the underlying code, while /MD results in incorrect functionality? A little background...somebody else developed the DLL in C++ and I am using this DLL in a VB.net application.

    Read the article

  • iPhone CoreData join

    - by Ken
    Hi guys, long time reader, first time poster. (A link to this schema is located here) http://www.weeshsoft.com/pix/DatabasePic.jpg I'm trying to get all LanguageEntries from a database for a given category.categoryName and languageset.languageSetName e.g. NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"LanguageEntry" inManagedObjectContext:del.managedObjectContext]; [fetchRequest setEntity:entity]; NSString* predicateString = [NSString stringWithFormat:@"Category.categoryName = %@ AND LanguageSet.languageSetName = %@", @"Food", @"English####Spanish"]; fetchRequest.predicate = [NSPredicate predicateWithFormat:predicateString]; NSError *error = nil; NSArray* objects = [del.managedObjectContext executeFetchRequest:fetchRequest error:&error]; This always returns 0 objects. If I set the predicate string to match on one relationship (e.g. Category.categoryName = Food or languageSet.languageSetName = English####Spanish) it will return data. This is baffling, can anyone shed some light? -Ken

    Read the article

< Previous Page | 434 435 436 437 438 439 440 441 442 443 444 445  | Next Page >