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  • OWB 11gR2 &ndash; Degenerate Dimensions

    - by David Allan
    Ever wondered how to build degenerate dimensions in OWB and get the benefits of slowly changing dimensions and cube loading? Now its possible through some changes in 11gR2 to make the dimension and cube loading much more flexible. This will let you get the benefits of OWB's surrogate key handling and slowly changing dimension reference when loading the fact table and need degenerate dimensions (see Ralph Kimball's degenerate dimensions design tip). Here we will see how to use the cube operator to load slowly changing, regular and degenerate dimensions. The cube and cube operator can now work with dimensions which have no surrogate key as well as dimensions with surrogates, so you can get the benefit of the cube loading and incorporate the degenerate dimension loading. What you need to do is create a dimension in OWB that is purely used for ETL metadata; the dimension itself is never deployed (its table is, but has not data) it has no surrogate keys has a single level with a business attribute the degenerate dimension data and a dummy attribute, say description just to pass the OWB validation. When this degenerate dimension is added into a cube, you will need to configure the fact table created and set the 'Deployable' flag to FALSE for the foreign key generated to the degenerate dimension table. The degenerate dimension reference will then be in the cube operator and used when matching. Create the degenerate dimension using the regular wizard. Delete the Surrogate ID attribute, this is not needed. Define a level name for the dimension member (any name). After the wizard has completed, in the editor delete the hierarchy STANDARD that was automatically generated, there is only a single level, no need for a hierarchy and this shouldn't really be created. Deploy the implementing table DD_ORDERNUMBER_TAB, this needs to be deployed but with no data (the mapping here will do a left outer join of the source data with the empty degenerate dimension table). Now, go ahead and build your cube, use the regular TIMES dimension for example and your degenerate dimension DD_ORDERNUMBER, can add in SCD dimensions etc. Configure the fact table created and set Deployable to false, so the foreign key does not get generated. Can now use the cube in a mapping and load data into the fact table via the cube operator, this will look after surrogate lookups and slowly changing dimension references.   If you generate the SQL you will see the ON clause for matching includes the columns representing the degenerate dimension columns. Here we have seen how this use case for loading fact tables using degenerate dimensions becomes a whole lot simpler using OWB 11gR2. I'm sure there are other use cases where using this mix of dimensions with surrogate and regular identifiers is useful, Fact tables partitioned by date columns is another classic example that this will greatly help and make the cube operator much more useful. Good to hear any comments.

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  • Le MIT crée « Kinect du futur », un capteur capable de détecter et suivre les mouvements d'une personne derrière un mur

    Le MIT crée « Kinect du futur » un capteur capable de détecter et suivre les mouvements d'une personne derrière un murDes jeunes chercheurs du MIT viennent de rendre public leur nouveau système de localisation dans l'espace qui permet de détecter une personne (ne disposant d'aucun transmetteur sans fil courant) située derrière un mur.Baptisé « Kinect du futur » en référence à la caméra des consoles de jeux de la firme de Redmond, le nouveau système tire parti de la propriété réflective des ondes...

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  • Dynamically creating a Generic Type at Runtime

    - by Rick Strahl
    I learned something new today. Not uncommon, but it's a core .NET runtime feature I simply did not know although I know I've run into this issue a few times and worked around it in other ways. Today there was no working around it and a few folks on Twitter pointed me in the right direction. The question I ran into is: How do I create a type instance of a generic type when I have dynamically acquired the type at runtime? Yup it's not something that you do everyday, but when you're writing code that parses objects dynamically at runtime it comes up from time to time. In my case it's in the bowels of a custom JSON parser. After some thought triggered by a comment today I realized it would be fairly easy to implement two-way Dictionary parsing for most concrete dictionary types. I could use a custom Dictionary serialization format that serializes as an array of key/value objects. Basically I can use a custom type (that matches the JSON signature) to hold my parsed dictionary data and then add it to the actual dictionary when parsing is complete. Generic Types at Runtime One issue that came up in the process was how to figure out what type the Dictionary<K,V> generic parameters take. Reflection actually makes it fairly easy to figure out generic types at runtime with code like this: if (arrayType.GetInterface("IDictionary") != null) { if (arrayType.IsGenericType) { var keyType = arrayType.GetGenericArguments()[0]; var valueType = arrayType.GetGenericArguments()[1]; … } } The GetArrayType method gets passed a type instance that is the array or array-like object that is rendered in JSON as an array (which includes IList, IDictionary, IDataReader and a few others). In my case the type passed would be something like Dictionary<string, CustomerEntity>. So I know what the parent container class type is. Based on the the container type using it's then possible to use GetGenericTypeArguments() to retrieve all the generic types in sequential order of definition (ie. string, CustomerEntity). That's the easy part. Creating a Generic Type and Providing Generic Parameters at RunTime The next problem is how do I get a concrete type instance for the generic type? I know what the type name and I have a type instance is but it's generic, so how do I get a type reference to keyvaluepair<K,V> that is specific to the keyType and valueType above? Here are a couple of things that come to mind but that don't work (and yes I tried that unsuccessfully first): Type elementType = typeof(keyvalue<keyType, valueType>); Type elementType = typeof(keyvalue<typeof(keyType), typeof(valueType)>); The problem is that this explicit syntax expects a type literal not some dynamic runtime value, so both of the above won't even compile. I turns out the way to create a generic type at runtime is using a fancy bit of syntax that until today I was completely unaware of: Type elementType = typeof(keyvalue<,>).MakeGenericType(keyType, valueType); The key is the type(keyvalue<,>) bit which looks weird at best. It works however and produces a non-generic type reference. You can see the difference between the full generic type and the non-typed (?) generic type in the debugger: The nonGenericType doesn't show any type specialization, while the elementType type shows the string, CustomerEntity (truncated above) in the type name. Once the full type reference exists (elementType) it's then easy to create an instance. In my case the parser parses through the JSON and when it completes parsing the value/object it creates a new keyvalue<T,V> instance. Now that I know the element type that's pretty trivial with: // Objects start out null until we find the opening tag resultObject = Activator.CreateInstance(elementType); Here the result object is picked up by the JSON array parser which creates an instance of the child object (keyvalue<K,V>) and then parses and assigns values from the JSON document using the types  key/value property signature. Internally the parser then takes each individually parsed item and adds it to a list of  List<keyvalue<K,V>> items. Parsing through a Generic type when you only have Runtime Type Information When parsing of the JSON array is done, the List needs to be turned into a defacto Dictionary<K,V>. This should be easy since I know that I'm dealing with an IDictionary, and I know the generic types for the key and value. The problem is again though that this needs to happen at runtime which would mean using several Convert.ChangeType() calls in the code to dynamically cast at runtime. Yuk. In the end I decided the easier and probably only slightly slower way to do this is a to use the dynamic type to collect the items and assign them to avoid all the dynamic casting madness: else if (IsIDictionary) { IDictionary dict = Activator.CreateInstance(arrayType) as IDictionary; foreach (dynamic item in items) { dict.Add(item.key, item.value); } return dict; } This code creates an instance of the generic dictionary type first, then loops through all of my custom keyvalue<K,V> items and assigns them to the actual dictionary. By using Dynamic here I can side step all the explicit type conversions that would be required in the three highlighted areas (not to mention that this nested method doesn't have access to the dictionary item generic types here). Static <- -> Dynamic Dynamic casting in a static language like C# is a bitch to say the least. This is one of the few times when I've cursed static typing and the arcane syntax that's required to coax types into the right format. It works but it's pretty nasty code. If it weren't for dynamic that last bit of code would have been a pretty ugly as well with a bunch of Convert.ChangeType() calls to litter the code. Fortunately this type of type convulsion is rather rare and reserved for system level code. It's not every day that you create a string to object parser after all :-)© Rick Strahl, West Wind Technologies, 2005-2011Posted in .NET  CSharp   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • SQL SERVER – 2011 – Introduction to SEQUENCE – Simple Example of SEQUENCE

    - by pinaldave
    SQL Server 2011 will contain one of the very interesting feature called SEQUENCE. I have waited for this feature for really long time. I am glad it is here finally. SEQUENCE allows you to define a single point of repository where SQL Server will maintain in memory counter. USE AdventureWorks2008R2 GO CREATE SEQUENCE [Seq] AS [int] START WITH 1 INCREMENT BY 1 MAXVALUE 20000 GO SEQUENCE is very interesting concept and I will write few blog post on this subject in future. Today we will see only working example of the same. Let us create a sequence. We can specify various values like start value, increment value as well maxvalue. -- First Run SELECT NEXT VALUE FOR Seq, c.CustomerID FROM Sales.Customer c GO -- Second Run SELECT NEXT VALUE FOR Seq, c.AccountNumber FROM Sales.Customer c GO Once the sequence is defined, it can be fetched using following method. Every single time new incremental value is provided, irrespective of sessions. Sequence will generate values till the max value specified. Once the max value is reached, query will stop and will return error message. Msg 11728, Level 16, State 1, Line 2 The sequence object ‘Seq’ has reached its minimum or maximum value. Restart the sequence object to allow new values to be generated. We can restart the sequence from any particular value and it will work fine. -- Restart the Sequence ALTER SEQUENCE [Seq] RESTART WITH 1 GO -- Sequence Restarted SELECT NEXT VALUE FOR Seq, c.CustomerID FROM Sales.Customer c GO Let us do final clean up. -- Clean Up DROP SEQUENCE [Seq] GO There are lots of things one can find useful about this feature. We will see that in future posts. Here is the complete code for easy reference. USE AdventureWorks2008R2 GO CREATE SEQUENCE [Seq] AS [int] START WITH 1 INCREMENT BY 1 MAXVALUE 20000 GO -- First Run SELECT NEXT VALUE FOR Seq, c.CustomerID FROM Sales.Customer c GO -- Second Run SELECT NEXT VALUE FOR Seq, c.AccountNumber FROM Sales.Customer c GO -- Restart the Sequence ALTER SEQUENCE [Seq] RESTART WITH 1 GO -- Sequence Restarted SELECT NEXT VALUE FOR Seq, c.CustomerID FROM Sales.Customer c GO -- Clean Up DROP SEQUENCE [Seq] GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Smile sort son « Guide Michelin » 2013 de l'Open-Source, le Livre Blanc gratuit s'enrichit de rubriques sur le Cloud et le Big Data

    Smile sort son « Guide Michelin » 2013 de l'Open-Source Le Livre Blanc gratuit s'enrichit de rubriques sur le Cloud et le Big Data Pour l'édition 2013 de son Guide de référence sur l'open source, Smile a enrichit son Livre Blanc (285 pages) d'une trentaine de nouvelles solutions et de deux nouvelles rubriques (Cloud et Big Data). Plus 300 solutions y sont recensées (dont 200 évaluées dans le détail) dans plus de 40 domaines d'applications, répartis en trois « dimensions » (Infrastructure, Développement et couches intermédiaires, Applications). Le livre se présente sous la forme de fiches de présentation (version du produit, site web, aute...

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  • SSIS Catalog, Windows updates and deployment failures due to System.Core mismatch

    - by jamiet
    This is a heads-up for anyone doing development on SSIS. On my current project where we are implementing a SQL Server Integration Services (SSIS) 2012 solution we recently encountered a situation where we were unable to deploy any of our projects even though we had successfully deployed in the past. Any attempt to use the deployment wizard resulted in this error dialog: The text of the error (for all you search engine crawlers out there) was: A .NET Framework error occurred during execution of user-defined routine or aggregate "create_key_information": System.IO.FileLoadException: Could not load file or assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) ---> System.IO.FileLoadException: The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) System.IO.FileLoadException: System.IO.FileLoadException:     at Microsoft.SqlServer.IntegrationServices.Server.Security.CryptoGraphy.CreateSymmetricKey(String algorithm)    at Microsoft.SqlServer.IntegrationServices.Server.Security.CryptoGraphy.CreateKeyInformation(SqlString algorithmName, SqlBytes& key, SqlBytes& IV) . (Microsoft SQL Server, Error: 6522) After some investigation and a bit of back and forth with some very helpful members of the SSIS product team (hey Matt, Wee Hyong) it transpired that this was due to a .Net Framework fix that had been delivered via Windows Update. I took a look at the server update history and indeed there have been some recently applied .Net Framework updates: This fix had (in the words of Matt Masson) “somehow caused a mismatch on System.Core for SQLCLR” and, as you may know, SQLCLR is used heavily within the SSIS Catalog. The fix was pretty simple – restart SQL Server. This causes the assemblies to be upgraded automatically. If you are using Data Quality Services (DQS) you may have experienced similar problems which are documented at Upgrade SQLCLR Assemblies After .NET Framework Update. I am hoping the SSIS team will follow-up with a more thorough explanation on their blog soon. You DBAs out there may be questioning why Windows Update is set to automatically apply updates on our production servers. We’re checking that out with our hosting provider right now You have been warned! @Jamiet

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  • SQL SERVER – Rename Columnname or Tablename – SQL in Sixty Seconds #032 – Video

    - by pinaldave
    We all make mistakes at some point of time and we all change our opinion. There are quite a lot of people in the world who have changed their name after they have grown up. Some corrected their parent’s mistake and some create new mistake. Well, databases are not protected from such incidents. There are many reasons why developers may want to change the name of the column or table after it was initially created. The goal of this video is not to dwell on the reasons but to learn how we can rename the column and table. Earlier I have written the article on this subject over here: SQL SERVER – How to Rename a Column Name or Table Name. I have revised the same article over here and created this video. There is one very important point to remember that by changing the column name or table name one creates the possibility of errors in the application the columns and tables are used. When any column or table name is changed, the developer should go through every place in the code base, ad-hoc queries, stored procedures, views and any other place where there are possibility of their usage and change them to the new name. If this is one followed up religiously there are quite a lot of changes that application will stop working due to this name change.  One has to remember that changing column name does not change the name of the indexes, constraints etc and they will continue to reference the old name. Though this will not stop the show but will create visual un-comfort as well confusion in many cases. Here is my question back to you – have you changed ever column name or table name in production database (after project going live)? If yes, what was the scenario and need of doing it. After all it is just a name. Let me know what you think of this video. Here is the updated script. USE tempdb GO CREATE TABLE TestTable (ID INT, OldName VARCHAR(20)) GO INSERT INTO TestTable VALUES (1, 'First') GO -- Check the Tabledata SELECT * FROM TestTable GO -- Rename the ColumnName sp_RENAME 'TestTable.OldName', 'NewName', 'Column' GO -- Check the Tabledata SELECT * FROM TestTable GO -- Rename the TableName sp_RENAME 'TestTable', 'NewTable' GO -- Check the Tabledata - Error SELECT * FROM TestTable GO -- Check the Tabledata - New SELECT * FROM NewTable GO -- Cleanup DROP TABLE NewTable GO Related Tips in SQL in Sixty Seconds: SQL SERVER – How to Rename a Column Name or Table Name What would you like to see in the next SQL in Sixty Seconds video? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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  • Bancassurers Seek IT Solutions to Support Distribution Model

    - by [email protected]
    Oracle Insurance's director of marketing for EMEA, John Sinclair, attended the third annual Bancassurance Forum in Vienna last month. He reports that the outlook for bancassurance in EMEA remains positive, despite changing market conditions that have led a number of bancassurers to re-examine their business models. Vienna is at the crossroads between mature Western European markets, where bancassurance is now an established best practice, and more recently tapped Eastern European markets that offer the greatest growth potential. Attendance at the Bancassurance Forum was good, with 87 bancassurance attendees, most in very senior positions in the industry. The conference provided the chance for a lively discussion among bancassurers looking to keep abreast of the latest trends in one of Europe's most successful distribution models for insurance. Even under normal business conditions, there is a great demand for best practice sharing within the industry as there is no standard formula for success.  Each company has to chart its own course and choose the strategies for sales, products development and the structure of ownership that make sense for their business, and as soon as they get it right bancassurers need to adapt the mix to keep up with ever changing regulations, completion and economic conditions.  To optimize the overall relationship between banking and insurance for mutual benefit, a balance needs to be struck between potentially conflicting interests. The banking side of the house is looking for greater wallet share from its customers and the ability to increase profitability by bundling insurance products with higher margins - especially in light of the recent economic crisis, where margins for traditional banking products are low and completion high. The insurance side of the house seeks access to new customers through a complementary distribution channel that is efficient and cost effective. To make the relationship work, it is important that both sides of the same house forge strategic and long term relationships - irrespective of whether the underlying business model is supported by a distribution agreement, cross-ownership or other forms of capital structure. However, this third annual conference was not held under normal business conditions. The conference took place in challenging, yet interesting times. ING's forced spinoff of its insurance operations under pressure by the EU Commission and the troubling losses suffered by Allianz as a result of the Dresdner bank sale were fresh in everyone's mind. One year after markets crashed, there is now enough hindsight to better understand the implications for bancassurance and best practices that are emerging to deal with them. The loan-driven business that has been crucial to bancassurance up till now evaporated during the crisis, leaving bancassurers grappling with how to change their overall strategy from a loan-driven to a more diversified model.  Attendees came to the conference to learn what strategies were working - not only to cope with the market shift, but to take advantage of it as markets pick up. Over the course of 14 customer case studies and numerous analyst presentations, topical issues ranging from getting the business model right to the impact on capital structuring of Solvency II were debated openly. Many speakers alluded to the need to specifically design insurance products with the banking distribution channel in mind, which brings with it specific requirements such as a high degree of standardization to achieve efficiency and reduce training costs. Moreover, products must be engineered to suit end consumers who consider banks a one-stop shop. The importance of IT to the successful implementation of bancassurance strategies was a theme that surfaced regularly throughout the conference.  The cross-selling opportunity - that will ultimately determine the success or failure of any bancassurance model - can only be fully realized through a flexible IT architecture that enables banking and insurance processes to be integrated and presented to front-line staff through a common interface. However, the reality is that most bancassurers have legacy IT systems, which constrain the businesses' ability to implement new strategies to maintaining competitiveness in turbulent times. My colleague Glenn Lottering, who chaired the conference, believes that the primary opportunities for bancassurers to extract value from their IT infrastructure investments lie in distribution management, risk management with the advent of Solvency II, and achieving operational excellence. "Oracle is ideally suited to meet the needs of bancassurance," Glenn noted, "supplying market-leading software for both banking and insurance. Oracle provides adaptive systems that let customers easily integrate hybrid business processes from both worlds while leveraging existing IT infrastructure." Overall, the consensus at the conference was that the outlook for bancassurance in EMEA remains positive, despite changing market conditions that have led a number of bancassurers to re-examine their business models. John Sinclair is marketing director for Oracle Insurance in EMEA. He has more than 20 years of experience in insurance and financial services.    

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  • links for 2010-04-06

    - by Bob Rhubart
    Dean Halbeisen: Best Practices for Network Backup (Sun StorageTek) Dean Halbeisen's white paper describes the Oracle reference architecture for next-generation data backup using Sun StorageTek Enterprise Backup software. (tags: entarch oracle otn sun enterprisearchitecture storagetek)

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  • Mise à jour du cours vidéo Python pour débutants par Pythonnerie, trois nouvelles vidéos sur les interfaces graphiques

    voici un tutoriel, destiné à des débutants en informatique, utilise la vidéo pour aider à visualiser les concepts. Cours vidéo Python pour débutants Ce tutoriel est un travail en cours, qui sera (doucement) enrichi et complété au fil du temps. Bien entendu, il n'a aucune prétention à remplacer la documentation de référence, qu'il espère simplement rendre indirectement plus accessible. Mais son auteur espère avoir confirmé le goût de l'informatique chez ceux qui l'avaient déjà et montré aux autres que la programmation n'est pas forcément rébarbative ni mystérieuse....

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  • SQL Server Installation Checklist

    - by Jonathan Kehayias
    The other night I was asked on Twitter by Todd McDonald (Twitter), for a build list for SQL Server 2005 and 2008.  My initial response was to provide a link to the SQL Server Build List Blog , which documents all of the builds of SQL Server and provides links to the KB articles associated with the builds.  However, this wasn’t what Todd was after, he actually wanted a reference for an installation checklist for SQL Server.  I have a number of these that I use in my job, and they vary...(read more)

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  • Oracle at The Forrester Customer Intelligence and Marketing Leadership Forums

    - by Christie Flanagan
    The Forrester Customer Intelligence Forum and the Forrester Marketing Leadership Forums will soon be here.  This year’s events will be co-located on April 18-19 at the J.W. Marriott at the L.A. Live entertainment complex in downtown Los Angeles.  Last year’s Marketing Forum was quite memorable for me.  You see, while Forrester analysts and business marketers were busy mingling over at the Marriott, another marketing powerhouse was taking up residence a few feet away at The Staples Center.  That’s right folks. Lada Gaga was coming to town.  And, as I came to learn, it made perfect sense for Lady Gaga and her legions of fans to be sharing a small patch of downtown L.A. with marketing leaders from all over the world.  After all, whether you like Lady Gaga or not, what pop star in recent memory has done more to build herself into a brand and to create an engaging, social and interactive customer experience for her Little Monsters?  While Lady Gaga won’t be back in town for this year’s Forrester events, there are still plenty of compelling reasons to make the trip out to Los Angeles.   The theme for The Forrester Customer Intelligence and Marketing Leadership Forums this year is “From Cool To Critical: Creating Engagement In The Age Of The Customer” and will tackle the important questions about how marketers can survive and thrive in the age of the empowered customer: •    How can you assess consumer uptake of new innovations?•    How do you build deep customer knowledge to drive competitive advantage?•    How do you drive deep, personalized customer engagement?•    What is more valuable — eyeballs or engagement?•    How do business customers engage in new media types?•    How can you tie social data to corporate data?•    Who should lead the movement to customer obsession?•    How should you shift your planning and measurement approaches to accommodate more data and a higher signal-to-noise ratio?•    What role does technology play in customizing and synchronizing marketing efforts across channels?As a platinum sponsor of the event, there will be a numbers of ways to interact with Oracle while you’re attending the Forums.  Here are some of the highlights:Oracle Speaking SessionThursday, April 19, 9:15am – 9:55amMaximize Customer Engagement and Retention with Integrated Marketing & LoyaltyMelissa Boxer, Vice President, Oracle CRM Marketing & LoyaltyCustomers expect to interact with your company, brand and products in more ways than ever before.   New devices and channels, such as mobile, social and web, are creating radical shifts in the customer buying process and the ways your company can reach and communicate with existing and potential customers. While Marketing's objectives (attract, convert, retain) remain fundamentally the same, your approach and tools must adapt quickly to succeed in this more complex, cross-channel world. Hear how leading brands are using Oracle's integrated marketing and loyalty solutions to maximize customer engagement and retention through better planning, execution, and measurement of synchronized cross-channel marketing initiatives.Solution ShowcaseWednesday, April 1810:20am – 11:50am 12:30pm – 1:30pm2:55pm – 3:40pmThursday, April 199:55am – 10:40am12:00pm – 1:00pmSolution Showcase & Networking ReceptionWednesday, April 185:10pm – 6:20pmBe sure to follow the #webcenter hashtag for updates on these events.  And for a more considered perspective on what Lady Gaga can teach businesses about branding and customer experience, check out Denise Lee Yohn’s post, Lessons from Lady Gaga from the Brand as Business Bites blog.

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  • SQL SERVER – Identify Numbers of Non Clustered Index on Tables for Entire Database

    - by pinaldave
    Here is the script which will give you numbers of non clustered indexes on any table in entire database. SELECT COUNT(i.TYPE) NoOfIndex, [schema_name] = s.name, table_name = o.name FROM sys.indexes i INNER JOIN sys.objects o ON i.[object_id] = o.[object_id] INNER JOIN sys.schemas s ON o.[schema_id] = s.[schema_id] WHERE o.TYPE IN ('U') AND i.TYPE = 2 GROUP BY s.name, o.name ORDER BY schema_name, table_name Here is the small story behind why this script was needed. I recently went to meet my friend in his office and he introduced me to his colleague in office as someone who is an expert in SQL Server Indexing. I politely said I am yet learning about Indexing and have a long way to go. My friend’s colleague right away said – he had a suggestion for me with related to Index. According to him he was looking for a script which will count all the non clustered on all the tables in the database and he was not able to find that on SQLAuthority.com. I was a bit surprised as I really do not remember all the details about what I have written so far. I quickly pull up my phone and tried to look for the script on my custom search engine and he was correct. I never wrote a script which will count all the non clustered indexes on tables in the whole database. Excessive indexing is not recommended in general. If you have too many indexes it will definitely negatively affect your performance. The above query will quickly give you details of numbers of indexes on tables on your entire database. You can quickly glance and use the numbers as reference. Please note that the number of the index is not a indication of bad indexes. There is a lot of wisdom I can write here but that is not the scope of this blog post. There are many different rules with Indexes and many different scenarios. For example – a table which is heap (no clustered index) is often not recommended on OLTP workload (here is the blog post to identify them), drop unused indexes with careful observation (here is the script for it), identify missing indexes and after careful testing add them (here is the script for it). Even though I have given few links here it is just the tip of the iceberg. If you follow only above four advices your ship may still sink. Those who wants to learn the subject in depth can watch the videos here after logging in. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Computer Science: Arts or Science?

    - by sunpech
    Various colleges and universities may offer a degree in Computer Science either as an Arts or a Science. What differences are there between the two? Would recruiters and those who conduct interviews favor one over the other? (Bachelor of Arts vs Bachelor of Sciences etc...) Update - Just wanted to add this link to Joel Spolsky's site to give a better frame of reference: BA or BS in Computer Science

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  • What is PubSubHubbub?

    What is PubSubHubbub? An overview of pubsubhubbub, a simple, open, web-hook-based pubsub protocol & open source reference implementation. Brett Slatkin and Brad Fitzpatrick demonstrate what pubsubhubbub is and how it works. For more information, visit pubsubhubbub.googlecode.com From: GoogleDevelopers Views: 23753 112 ratings Time: 03:20 More in Science & Technology

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  • Silverlight Cream for June 10, 2010 -- #879

    - by Dave Campbell
    In this Issue: Emiel Jongerius, Nokola, Christian Schormann, Tim Heuer, David Poll, Mike Snow(-2-), John Papa, and Charles Petzold. Shoutout: Viktor Larsson has a frank look at WP7 based on information from MIX10 and what was said this week in his post: Licking Windows Phone 7... yeah licking, not liking :) .. my guess is even that didn't allow him to keep it! If you haven't already noticed, the CodeProject reader's choice awards are out this week and Telerik won for their RadColorPicker and RadCalendar for Silverlight Telerik also needs congratulations for winning Telerik wins “Best of TechEd” award in the “Components and Middleware” category... check out that trophy... Steven Forte has a picture up of the Telerikers after getting the award. Koen Zwikstra has a new release of Silverlight Spy up that supports the latest release: Silverlight Spy 3.0.0.12 From SilverlightCream.com: Localization of XAML files in Silverlight Emiel Jongerius is back with another post, this time discussing Localizing XAM files... external links and source included. Coolest Silverlight Sound Library for Games I've Seen Yet Nokola talks up a Sound Library for Silverlight 4 Games ... and has links to a great demo, plus the source. SketchFlow: Firing Actions when a Storyboard is Complete Christian Schormann responded to some Twitter questions and demonstrates using the StoryboardCompleted trigger with a Navigate action. Hosting cross-domain Silverlight applications (XAP) Tim Heuer responds to a question from a reader and demonstrates how to host a XAP from a domain other than the one you're working on. Taking Microsoft Silverlight 4 Applications Beyond the Browser (TechEd WEB313) David Poll has all his material up from his TechEd presentation earlier this week on Silverlight OOB... and he covered some pretty extensive material ... check it out! Silverlight Tip of the Day #29 – Configuring Service Reference to Back to LocalHost Mike Snow has a couple new tips up... this first one is quick, but very useful... how to switch your service reference back to localhost without pulling out your hair. Silverlight Tip of the Day #30 – Sending Email from Silverlight In Mike Snow's latest tip, he shows how to send email from your Silverlight app... using a WCF service... and a step-by-step set of instructions. Creating Rich Interactions Using Blend 4: Transition Effects, Fluid Layout and Layout States (Silverlight TV #32) John Papa has Silverlight TV #32 up, and he's talking with Kenny Young of the Expression Blend team while Kenny uses some built-om effects and also creates some impressive examples from scratch -- code included. Simulating Touch Inertia on Windows Phone 7 Charles Petzold has a post up on simulating inertia on WP7... demos in WPF and then moves into WP7... math, source, and external links. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • How to wire finite state machine into component-based architecture?

    - by Pup
    State machines seem to cause harmful dependencies in component-based architectures. How, specifically, is communication handled between a state machine and the components that carry out state-related behavior? Where I'm at: I'm new to component-based architectures. I'm making a fighting game, although I don't think that should matter. I envision my state machine being used to toggle states like "crouching", "dashing", "blocking", etc. I've found this state-management technique to be the most natural system for a component-based architecture, but it conflicts with techniques I've read about: Dynamic Game Object Component System for Mutable Behavior Characters It suggests that all components activate/deactivate themselves by continually checking a condition for activation. I think that actions like "running" or "walking" make sense as states, which is in disagreement with the accepted response here: finite state machine used in mario like platform game I've found this useful, but ambiguous: How to implement behavior in a component-based game architecture? It suggests having a separate component that contains nothing but a state machine. But, this necessitates some kind of coupling between the state machine component and nearly all the other components. I don't understand how this coupling should be handled. These are some guesses: A. Components depend on state machine: Components receive reference to state machine component's getState(), which returns an enumeration constant. Components update themselves regularly and check this as needed. B. State machine depends on components: The state machine component receives references to all the components it's monitoring. It queries their getState() methods to see where they're at. C. Some abstraction between them Use an event hub? Command pattern? D. Separate state objects that reference components State Pattern is used. Separate state objects are created, which activate/deactivate a set of components. State machine switches between state objects. I'm looking at components as implementations of aspects. They do everything that's needed internally to make that aspect happen. It seems like components should function on their own, without relying on other components. I know some dependencies are necessary, but state machines seem to want to control all of my components.

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  • Évènement : eMetrics Marketing Optimization Summit, le salon de l'optimisation marketing et de la Bu

    eMetrics Marketing Optimization / SMX - l'événement webmarketing à ne pas manquer La première en France et ce sera au Hilton à Paris le 15 et 16 juin Le sommet eMetrics Marketing Optimization - l´évènement international de référence pour l´e-marketing et le « Web Analytics » - fera son entrée en France, pour la première fois le 15 et 16 juin 2010 à Paris. Depuis 2002, c´est la plateforme de rencontre des responsables marketing, des analystes web et des experts en business intelligence qui souhaitent augmenter leur retour sur investissements en ligne. Il est généralement mené en parallèle avec

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  • Oracle Technológia Fórum rendezvény, 2010. május 5. szerda

    - by Fekete Zoltán
    Jövo hét szerdán Oracle Technology Fórum napot tartunk, ahol az adatbázis-kezelési és a fejlesztoi szekciókban hallgathatók meg eloadások illetve kaphatók válaszok a kérdésekre. Jelentkezés a rendezvényre. Az adatbázis szekcióban fogok beszélni a Sun Oracle Database Machine / Exadata megoldások technikai gyöngyszemeirol mind a tranzakciós (OLTP) mind az adattárházas (DW) és adatbázis konszolidáció oldaláról. Emellett kiemelem majd az Oracle Data Mining (adatbányászat) és OLAP újdonságait, érdekességeit. Megemlítem majd az Oracle's Data Warehouse Reference Architecture alkalmazási lehetoségeit is.

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  • SQL SERVER – Weekly Series – Memory Lane – #035

    - by Pinal Dave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Row Overflow Data Explanation  In SQL Server 2005 one table row can contain more than one varchar(8000) fields. One more thing, the exclusions has exclusions also the limit of each individual column max width of 8000 bytes does not apply to varchar(max), nvarchar(max), varbinary(max), text, image or xml data type columns. Comparison Index Fragmentation, Index De-Fragmentation, Index Rebuild – SQL SERVER 2000 and SQL SERVER 2005 An old but like a gold article. Talks about lots of concepts related to Index and the difference from earlier version to the newer version. I strongly suggest that everyone should read this article just to understand how SQL Server has moved forward with the technology. Improvements in TempDB SQL Server 2005 had come up with quite a lots of improvements and this blog post describes them and explains the same. If you ask me what is my the most favorite article from early career. I must point out to this article as when I wrote this one I personally have learned a lot of new things. Recompile All The Stored Procedure on Specific TableI prefer to recompile all the stored procedure on the table, which has faced mass insert or update. sp_recompiles marks stored procedures to recompile when they execute next time. This blog post explains the same with the help of a script.  2008 SQLAuthority Download – SQL Server Cheatsheet You can download and print this cheat sheet and use it for your personal reference. If you have any suggestions, please let me know and I will see if I can update this SQL Server cheat sheet. Difference Between DBMS and RDBMS What is the difference between DBMS and RDBMS? DBMS – Data Base Management System RDBMS – Relational Data Base Management System or Relational DBMS High Availability – Hot Add Memory Hot Add CPU and Hot Add Memory are extremely interesting features of the SQL Server, however, personally I have not witness them heavily used. These features also have few restriction as well. I blogged about them in detail. 2009 Delete Duplicate Rows I have demonstrated in this blog post how one can identify and delete duplicate rows. Interesting Observation of Logon Trigger On All Servers – Solution The question I put forth in my previous article was – In single login why the trigger fires multiple times; it should be fired only once. I received numerous answers in thread as well as in my MVP private news group. Now, let us discuss the answer for the same. The answer is – It happens because multiple SQL Server services are running as well as intellisense is turned on. Blog post demonstrates how we can do the same with the help of SQL scripts. Management Studio New Features I have selected my favorite 5 features and blogged about it. IntelliSense for Query Editing Multi Server Query Query Editor Regions Object Explorer Enhancements Activity Monitors Maximum Number of Index per Table One of the questions I asked in my user group was – What is the maximum number of Index per table? I received lots of answers to this question but only two answers are correct. Let us now take a look at them in this blog post. 2010 Default Statistics on Column – Automatic Statistics on Column The truth is, Statistics can be in a table even though there is no Index in it. If you have the auto- create and/or auto-update Statistics feature turned on for SQL Server database, Statistics will be automatically created on the Column based on a few conditions. Please read my previously posted article, SQL SERVER – When are Statistics Updated – What triggers Statistics to Update, for the specific conditions when Statistics is updated. 2011 T-SQL Scripts to Find Maximum between Two Numbers In this blog post there are two different scripts listed which demonstrates way to find the maximum number between two numbers. I need your help, which one of the script do you think is the most accurate way to find maximum number? Find Details for Statistics of Whole Database – DMV – T-SQL Script I was recently asked is there a single script which can provide all the necessary details about statistics for any database. This question made me write following script. I was initially planning to use sp_helpstats command but I remembered that this is marked to be deprecated in future. 2012 Introduction to Function SIGN SIGN Function is very fundamental function. It will return the value 1, -1 or 0. If your value is negative it will return you negative -1 and if it is positive it will return you positive +1. Let us start with a simple small example. Template Browser – A Very Important and Useful Feature of SSMS Templates are like a quick cheat sheet or quick reference. Templates are available to create objects like databases, tables, views, indexes, stored procedures, triggers, statistics, and functions. Templates are also available for Analysis Services as well. The template scripts contain parameters to help you customize the code. You can Replace Template Parameters dialog box to insert values into the script. An invalid floating point operation occurred If you run any of the above functions they will give you an error related to invalid floating point. Honestly there is no workaround except passing the function appropriate values. SQRT of a negative number will give you result in real numbers which is not supported at this point of time as well LOG of a negative number is not possible (because logarithm is the inverse function of an exponential function and the exponential function is NEVER negative). Validating Spatial Object with IsValidDetailed Function SQL Server 2012 has introduced the new function IsValidDetailed(). This function has made my life very easy. In simple words, this function will check if the spatial object passed is valid or not. If it is valid it will give information that it is valid. If the spatial object is not valid it will return the answer that it is not valid and the reason for the same. This makes it very easy to debug the issue and make the necessary correction. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • IntelliSense for Razor Hosting in non-Web Applications

    - by Rick Strahl
    When I posted my Razor Hosting article a couple of weeks ago I got a number of questions on how to get IntelliSense to work inside of Visual Studio while editing your templates. The answer to this question is mainly dependent on how Visual Studio recognizes assemblies, so a little background is required. If you open a template just on its own as a standalone file by clicking on it say in Explorer, Visual Studio will open up with the template in the editor, but you won’t get any IntelliSense on any of your related assemblies that you might be using by default. It’ll give Intellisense on base System namespace, but not on your imported assembly types. This makes sense: Visual Studio has no idea what the assembly associations for the single file are. There are two options available to you to make IntelliSense work for templates: Add the templates as included files to your non-Web project Add a BIN folder to your template’s folder and add all assemblies required there Including Templates in your Host Project By including templates into your Razor hosting project, Visual Studio will pick up the project’s assembly references and make IntelliSense available for any of the custom types in your project and on your templates. To see this work I moved the \Templates folder from the samples from the Debug\Bin folder into the project root and included the templates in the WinForm sample project. Here’s what this looks like in Visual Studio after the templates have been included:   Notice that I take my original example and type cast the Context object to the specific type that it actually represents – namely CustomContext – by using a simple code block: @{ CustomContext Model = Context as CustomContext; } After that assignment my Model local variable is in scope and IntelliSense works as expected. Note that you also will need to add any namespaces with the using command in this case: @using RazorHostingWinForm which has to be defined at the very top of a Razor document. BTW, while you can only pass in a single Context 'parameter’ to the template with the default template I’ve provided realize that you can also assign a complex object to Context. For example you could have a container object that references a variety of other objects which you can then cast to the appropriate types as needed: @{ ContextContainer container = Context as ContextContainer; CustomContext Model = container.Model; CustomDAO DAO = container.DAO; } and so forth. IntelliSense for your Custom Template Notice also that you can get IntelliSense for the top level template by specifying an inherits tag at the top of the document: @inherits RazorHosting.RazorTemplateFolderHost By specifying the above you can then get IntelliSense on your base template’s properties. For example, in my base template there are Request and Response objects. This is very useful especially if you end up creating custom templates that include your custom business objects as you can get effectively see full IntelliSense from the ‘page’ level down. For Html Help Builder for example, I’d have a Help object on the page and assuming I have the references available I can see all the way into that Help object without even having to do anything fancy. Note that the @inherits key is a GREAT and easy way to override the base template you normally specify as the default template. It allows you to create a custom template and as long as it inherits from the base template it’ll work properly. Since the last post I’ve also made some changes in the base template that allow hooking up some simple initialization logic so it gets much more easy to create custom templates and hook up custom objects with an IntializeTemplate() hook function that gets called with the Context and a Configuration object. These objects are objects you can pass in at runtime from your host application and then assign to custom properties on your template. For example the default implementation for RazorTemplateFolderHost does this: public override void InitializeTemplate(object context, object configurationData) { // Pick up configuration data and stuff into Request object RazorFolderHostTemplateConfiguration config = configurationData as RazorFolderHostTemplateConfiguration; this.Request.TemplatePath = config.TemplatePath; this.Request.TemplateRelativePath = config.TemplateRelativePath; // Just use the entire ConfigData as the model, but in theory // configData could contain many objects or values to set on // template properties this.Model = config.ConfigData as TModel; } to set up a strongly typed Model and the Request object. You can do much more complex hookups here of course and create complex base template pages that contain all the objects that you need in your code with strong typing. Adding a Bin folder to your Template’s Root Path Including templates in your host project works if you own the project and you’re the only one modifying the templates. However, if you are distributing the Razor engine as a templating/scripting solution as part of your application or development tool the original project is likely not available and so that approach is not practical. Another option you have is to add a Bin folder and add all the related assemblies into it. You can also add a Web.Config file with assembly references for any GAC’d assembly references that need to be associated with the templates. Between the web.config and bin folder Visual Studio can figure out how to provide IntelliSense. The Bin folder should contain: The RazorHosting.dll Your host project’s EXE or DLL – renamed to .dll if it’s an .exe Any external (bin folder) dependent assemblies Note that you most likely also want a reference to the host project if it contains references that are going to be used in templates. Visual Studio doesn’t recognize an EXE reference so you have to rename the EXE to DLL to make it work. Apparently the binary signature of EXE and DLL files are identical and it just works – learn something new everyday… For GAC assembly references you can add a web.config file to your template root. The Web.config file then should contain any full assembly references to GAC components: <configuration> <system.web> <compilation debug="true"> <assemblies> <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> <add assembly="System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /> <add assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> </assemblies> </compilation> </system.web> </configuration> And with that you should get full IntelliSense. Note that if you add a BIN folder and you also have the templates in your Visual Studio project Visual Studio will complain about reference conflicts as it’s effectively seeing both the project references and the ones in the bin folder. So it’s probably a good idea to use one or the other but not both at the same time :-) Seeing IntelliSense in your Razor templates is a big help for users of your templates. If you’re shipping an application level scripting solution especially it’ll be real useful for your template consumers/users to be able to get some quick help on creating customized templates – after all that’s what templates are all about – easy customization. Making sure that everything is referenced in your bin folder and web.config is a good idea and it’s great to see that Visual Studio (and presumably WebMatrix/Visual Web Developer as well) will be able to pick up your custom IntelliSense in Razor templates.© Rick Strahl, West Wind Technologies, 2005-2011Posted in Razor  

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  • SQLAuthority News – New Book Released – SQL Server Interview Questions And Answers

    - by pinaldave
    Two days ago, on birthday of my blog – I asked simple question – Guess! What is in this box? I have received lots of interesting comments on the blog about what is in it. Many of you got it absolutely incorrect and many got it close to the right answer but no one got it 100% correct. Well, no issue at all, I am going to give away the price to whoever has the closest answer first in personal email. Here is the answer to the question about what is in the box? Here it is – the box has my new book. In fact, I should say our new book as I co-authored this book with my very good friend Vinod Kumar. We had real blast writing this book together and had lots of interesting conversation when we were writing this book. This book has one simple goal – “master the basics.” This book is not only for people who are preparing for interview. This book is for every one who wants to revisit the basics and wants to prepare themselves to the technology. One always needs to have practical knowledge to do their duty efficiently. This book talks about more than basics. There are multiple ways to present learning – either we can create simple book or make it interesting. We have decided the learning should be interactive and have opted for Interview Questions and Answer format. Here is quick interview which we have done together. Details of the books are here The core concept of this book will continue to evolve over time. I am sure many of you will come along with us on this journey and submit your suggestions to us to make this book a key reference for anybody who wants to start with SQL server. Today we want to acknowledge the fact that you will help us keep this book alive forever with the latest updates. We want to thank everyone who participates in this journey with us. You can get the books from [Amazon] | [Flipkart]. Read Vinod‘s blog post. Do not forget to wish him happy birthday as today is his birthday and also book release day – two reason to wish him congratulations. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Data Warehousing, Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, SQLAuthority News, SQLServer, T SQL, Technology

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  • How to Achieve OC4J RMI Load Balancing

    - by fip
    This is an old, Oracle SOA and OC4J 10G topic. In fact this is not even a SOA topic per se. Questions of RMI load balancing arise when you developed custom web applications accessing human tasks running off a remote SOA 10G cluster. Having returned from a customer who faced challenges with OC4J RMI load balancing, I felt there is still some confusions in the field how OC4J RMI load balancing work. Hence I decide to dust off an old tech note that I wrote a few years back and share it with the general public. Here is the tech note: Overview A typical use case in Oracle SOA is that you are building web based, custom human tasks UI that will interact with the task services housed in a remote BPEL 10G cluster. Or, in a more generic way, you are just building a web based application in Java that needs to interact with the EJBs in a remote OC4J cluster. In either case, you are talking to an OC4J cluster as RMI client. Then immediately you must ask yourself the following questions: 1. How do I make sure that the web application, as an RMI client, even distribute its load against all the nodes in the remote OC4J cluster? 2. How do I make sure that the web application, as an RMI client, is resilient to the node failures in the remote OC4J cluster, so that in the unlikely case when one of the remote OC4J nodes fail, my web application will continue to function? That is the topic of how to achieve load balancing with OC4J RMI client. Solutions You need to configure and code RMI load balancing in two places: 1. Provider URL can be specified with a comma separated list of URLs, so that the initial lookup will land to one of the available URLs. 2. Choose a proper value for the oracle.j2ee.rmi.loadBalance property, which, along side with the PROVIDER_URL property, is one of the JNDI properties passed to the JNDI lookup.(http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI) More details below: About the PROVIDER_URL The JNDI property java.name.provider.url's job is, when the client looks up for a new context at the very first time in the client session, to provide a list of RMI context The value of the JNDI property java.name.provider.url goes by the format of a single URL, or a comma separate list of URLs. A single URL. For example: opmn:ormi://host1:6003:oc4j_instance1/appName1 A comma separated list of multiple URLs. For examples:  opmn:ormi://host1:6003:oc4j_instanc1/appName, opmn:ormi://host2:6003:oc4j_instance1/appName, opmn:ormi://host3:6003:oc4j_instance1/appName When the client looks up for a new Context the very first time in the client session, it sends a query against the OPMN referenced by the provider URL. The OPMN host and port specifies the destination of such query, and the OC4J instance name and appName are actually the “where clause” of the query. When the PROVIDER URL reference a single OPMN server Let's consider the case when the provider url only reference a single OPMN server of the destination cluster. In this case, that single OPMN server receives the query and returns a list of the qualified Contexts from all OC4Js within the cluster, even though there is a single OPMN server in the provider URL. A context represent a particular starting point at a particular server for subsequent object lookup. For example, if the URL is opmn:ormi://host1:6003:oc4j_instance1/appName, then, OPMN will return the following contexts: appName on oc4j_instance1 on host1 appName on oc4j_instance1 on host2, appName on oc4j_instance1 on host3,  (provided that host1, host2, host3 are all in the same cluster) Please note that One OPMN will be sufficient to find the list of all contexts from the entire cluster that satisfy the JNDI lookup query. You can do an experiment by shutting down appName on host1, and observe that OPMN on host1 will still be able to return you appname on host2 and appName on host3. When the PROVIDER URL reference a comma separated list of multiple OPMN servers When the JNDI propery java.naming.provider.url references a comma separated list of multiple URLs, the lookup will return the exact same things as with the single OPMN server: a list of qualified Contexts from the cluster. The purpose of having multiple OPMN servers is to provide high availability in the initial context creation, such that if OPMN at host1 is unavailable, client will try the lookup via OPMN on host2, and so on. After the initial lookup returns and cache a list of contexts, the JNDI URL(s) are no longer used in the same client session. That explains why removing the 3rd URL from the list of JNDI URLs will not stop the client from getting the EJB on the 3rd server. About the oracle.j2ee.rmi.loadBalance Property After the client acquires the list of contexts, it will cache it at the client side as “list of available RMI contexts”.  This list includes all the servers in the destination cluster. This list will stay in the cache until the client session (JVM) ends. The RMI load balancing against the destination cluster is happening at the client side, as the client is switching between the members of the list. Whether and how often the client will fresh the Context from the list of Context is based on the value of the  oracle.j2ee.rmi.loadBalance. The documentation at http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI list all the available values for the oracle.j2ee.rmi.loadBalance. Value Description client If specified, the client interacts with the OC4J process that was initially chosen at the first lookup for the entire conversation. context Used for a Web client (servlet or JSP) that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be returned each time InitialContext() is invoked. lookup Used for a standalone client that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be created each time the client calls Context.lookup(). Please note the regardless of the setting of oracle.j2ee.rmi.loadBalance property, the “refresh” only occurs at the client. The client can only choose from the "list of available context" that was returned and cached from the very first lookup. That is, the client will merely get a new Context object from the “list of available RMI contexts” from the cache at the client side. The client will NOT go to the OPMN server again to get the list. That also implies that if you are adding a node to the server cluster AFTER the client’s initial lookup, the client would not know it because neither the server nor the client will initiate a refresh of the “list of available servers” to reflect the new node. About High Availability (i.e. Resilience Against Node Failure of Remote OC4J Cluster) What we have discussed above is about load balancing. Let's also discuss high availability. This is how the High Availability works in RMI: when the client use the context but get an exception such as socket is closed, it knows that the server referenced by that Context is problematic and will try to get another unused Context from the “list of available contexts”. Again, this list is the list that was returned and cached at the very first lookup in the entire client session.

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  • 5 Reasons why I hate WPF

    - by Richard Mitchell
    I decided to use writing a new tool as a way to learn WPF and MVVM and I thought I'd write down a few of my problems as a way of cathartic release. I decided to read a book before attempting WPF for the first time as I've heard others complain about the steep learning curve. I chose the rather excellent "WPF 4 Unleashed" by Adam Nathan to read through and "Pro WPF in C# 2010" by Matthew MacDonald as a reference whilst I programmed. 1 - Poor editing support for XAML The first thing I think any...(read more)

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