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  • Strange Locking Behaviour in SQL Server 2005

    - by SQL Learner
    Can anyone please tell me why does the following statement inside a given stored procedure returns repeated results even with locks on the rows used by the first SELECT statement? BEGIN TRANSACTION DECLARE @Temp TABLE ( ID INT ) INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue <= 10 INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue >= 5 SELECT * FROM @Temp COMMIT TRANSACTION Any values in SomeTable for which SomeValue is between 5 and 10 will be returned twice, even though they were locked in the first SELECT. I thought that locks were in place for the whole transaction, and so I wasn't expecting the query to return repeated results. Why is this happening?

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  • SQL: Interrupting a query

    - by NoozNooz42
    I've worked on a project using a proprietary non-SQL DB where queries could be interrupted and in the codebase there were quite some spots where that functionnality was used and made perfect sense (for example to stop a long running query that gets cancelled by the user, or when a more recent query takes place and renders the previous query obsolete, etc.) and I realized I never really saw that kind of "interrupted queries" previously and thought it could make a good SO question (several questions, but they're all related to exactly the same thing): can SQL queries be interrupted? is this part of the SQL standard? if it's not part of the SQL standard, which SQL DBs allow queries to be interrupted (any example most welcome)? is it common to interrupt a DB query (SQL or not) which you'll know you won't care about the result anymore? (in the codebase I've worked on, it sure helps lighten the server's load)

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  • SQL Server Editions and Integration Services

    The SQL Server 2005 and SQL Server 2008 product family has quite a few editions now, so what does this mean for SQL Server Integration Services? Starting from the bottom we have the free edition known as Express, and the entry level Workgroup edition, as well as the new Web edition. None of these three include the full SSIS product, but they do all include the SQL Server Import and Export Wizard, with access to basic data sources but nothing more, so for simple loading and extraction of data this should suffice. You will not be able to build packages though, this is just a one shot deal aimed at using the wizard on an ad-hoc basis. To get the full power of Integration Services you need to start with Standard edition. This includes the BI Development Studio, for building your own packages, and fully functional IDE integrated into Visual Studio. (You get the full VS 2005/2008 IDE with the product). All core functions will be available but with a restricted set of transformations and tasks. The SQL Server 2005 Features Comparison or Features Supported by the Editions of SQL Server 2008 describes standard edition as having basic transforms, compared to Enterprise which includes the advanced transforms. I think basic is a little harsh considering the power you get with Standard, but the advanced covers the truly ground-breaking capabilities of data mining, text mining and cleansing or fuzzy transforms. The power of performing these operations within your ETL pipeline should not be underestimated, but not all processes will require these capabilities, so it seems like a reasonable delineation. Thankfully there are no feature limitations or artificial governors within Standard compared to Enterprise. The same control flow and data flow engines underpin both editions, with the same configuration and deployment options allowing you to work seamlessly between environments and editions if using the common components. In fact there are no govenors at all in SSIS, so whilst the SQL Database engine is limited to 4 CPUs in Standard edition, SSIS is only limited by the base operating system. The advanced transforms only available with Enterprise edition: Data Mining Training Destination Data Mining Query Component Fuzzy Grouping Fuzzy Lookup Term Extraction Term Lookup Dimension Processing Destination Partition Processing Destination The advanced tasks only available with Enterprise edition: Data Mining Query Task So in summary, if you want SQL Server Integration Services, you need SQL Server Standard edition, and for the more advanced tasks and transforms you need SQL Server Enterprise edition. To recap, the answer to the often asked question is no, SQL Server Integration Services is not available in SQL Server Express or Workgroup editions.

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  • The Execute SQL Task

    In this article we are going to take you through the Execute SQL Task in SQL Server Integration Services for SQL Server 2005 (although it appies just as well to SQL Server 2008).  We will be covering all the essentials that you will need to know to effectively use this task and make it as flexible as possible. The things we will be looking at are as follows: A tour of the Task. The properties of the Task. After looking at these introductory topics we will then get into some examples. The examples will show different types of usage for the task: Returning a single value from a SQL query with two input parameters. Returning a rowset from a SQL query. Executing a stored procedure and retrieveing a rowset, a return value, an output parameter value and passing in an input parameter. Passing in the SQL Statement from a variable. Passing in the SQL Statement from a file. Tour Of The Task Before we can start to use the Execute SQL Task in our packages we are going to need to locate it in the toolbox. Let's do that now. Whilst in the Control Flow section of the package expand your toolbox and locate the Execute SQL Task. Below is how we found ours. Now drag the task onto the designer. As you can see from the following image we have a validation error appear telling us that no connection manager has been assigned to the task. This can be easily remedied by creating a connection manager. There are certain types of connection manager that are compatable with this task so we cannot just create any connection manager and these are detailed in a few graphics time. Double click on the task itself to take a look at the custom user interface provided to us for this task. The task will open on the general tab as shown below. Take a bit of time to have a look around here as throughout this article we will be revisting this page many times. Whilst on the general tab, drop down the combobox next to the ConnectionType property. In here you will see the types of connection manager which this task will accept. As with SQL Server 2000 DTS, SSIS allows you to output values from this task in a number of formats. Have a look at the combobox next to the Resultset property. The major difference here is the ability to output into XML. If you drop down the combobox next to the SQLSourceType property you will see the ways in which you can pass a SQL Statement into the task itself. We will have examples of each of these later on but certainly when we saw these for the first time we were very excited. Next to the SQLStatement property if you click in the empty box next to it you will see ellipses appear. Click on them and you will see the very basic query editor that becomes available to you. Alternatively after you have specified a connection manager for the task you can click on the Build Query button to bring up a completely different query editor. This is slightly inconsistent. Once you've finished looking around the general tab, move on to the next tab which is the parameter mapping tab. We shall, again, be visiting this tab throughout the article but to give you an initial heads up this is where you define the input, output and return values from your task. Note this is not where you specify the resultset. If however you now move on to the ResultSet tab this is where you define what variable will receive the output from your SQL Statement in whatever form that is. Property Expressions are one of the most amazing things to happen in SSIS and they will not be covered here as they deserve a whole article to themselves. Watch out for this as their usefulness will astound you. For a more detailed discussion of what should be the parameter markers in the SQL Statements on the General tab and how to map them to variables on the Parameter Mapping tab see Working with Parameters and Return Codes in the Execute SQL Task. Task Properties There are two places where you can specify the properties for your task. One is in the task UI itself and the other is in the property pane which will appear if you right click on your task and select Properties from the context menu. We will be doing plenty of property setting in the UI later so let's take a moment to have a look at the property pane. Below is a graphic showing our properties pane. Now we shall take you through all the properties and tell you exactly what they mean. A lot of these properties you will see across all tasks as well as the package because of everything's base structure The Container. BypassPrepare Should the statement be prepared before sending to the connection manager destination (True/False) Connection This is simply the name of the connection manager that the task will use. We can get this from the connection manager tray at the bottom of the package. DelayValidation Really interesting property and it tells the task to not validate until it actually executes. A usage for this may be that you are operating on table yet to be created but at runtime you know the table will be there. Description Very simply the description of your Task. Disable Should the task be enabled or not? You can also set this through a context menu by right clicking on the task itself. DisableEventHandlers As a result of events that happen in the task, should the event handlers for the container fire? ExecValueVariable The variable assigned here will get or set the execution value of the task. Expressions Expressions as we mentioned earlier are a really powerful tool in SSIS and this graphic below shows us a small peek of what you can do. We select a property on the left and assign an expression to the value of that property on the right causing the value to be dynamically changed at runtime. One of the most obvious uses of this is that the property value can be built dynamically from within the package allowing you a great deal of flexibility FailPackageOnFailure If this task fails does the package? FailParentOnFailure If this task fails does the parent container? A task can he hosted inside another container i.e. the For Each Loop Container and this would then be the parent. ForcedExecutionValue This property allows you to hard code an execution value for the task. ForcedExecutionValueType What is the datatype of the ForcedExecutionValue? ForceExecutionResult Force the task to return a certain execution result. This could then be used by the workflow constraints. Possible values are None, Success, Failure and Completion. ForceExecutionValue Should we force the execution result? IsolationLevel This is the transaction isolation level of the task. IsStoredProcedure Certain optimisations are made by the task if it knows that the query is a Stored Procedure invocation. The docs say this will always be false unless the connection is an ADO connection. LocaleID Gets or sets the LocaleID of the container. LoggingMode Should we log for this container and what settings should we use? The value choices are UseParentSetting, Enabled and Disabled. MaximumErrorCount How many times can the task fail before we call it a day? Name Very simply the name of the task. ResultSetType How do you want the results of your query returned? The choices are ResultSetType_None, ResultSetType_SingleRow, ResultSetType_Rowset and ResultSetType_XML. SqlStatementSource Your Query/SQL Statement. SqlStatementSourceType The method of specifying the query. Your choices here are DirectInput, FileConnection and Variables TimeOut How long should the task wait to receive results? TransactionOption How should the task handle being asked to join a transaction? Usage Examples As we move through the examples we will only cover in them what we think you must know and what we think you should see. This means that some of the more elementary steps like setting up variables will be covered in the early examples but skipped and simply referred to in later ones. All these examples used the AventureWorks database that comes with SQL Server 2005. Returning a Single Value, Passing in Two Input Parameters So the first thing we are going to do is add some variables to our package. The graphic below shows us those variables having been defined. Here the CountOfEmployees variable will be used as the output from the query and EndDate and StartDate will be used as input parameters. As you can see all these variables have been scoped to the package. Scoping allows us to have domains for variables. Each container has a scope and remember a package is a container as well. Variable values of the parent container can be seen in child containers but cannot be passed back up to the parent from a child. Our following graphic has had a number of changes made. The first of those changes is that we have created and assigned an OLEDB connection manager to this Task ExecuteSQL Task Connection. The next thing is we have made sure that the SQLSourceType property is set to Direct Input as we will be writing in our statement ourselves. We have also specified that only a single row will be returned from this query. The expressions we typed in was: SELECT COUNT(*) AS CountOfEmployees FROM HumanResources.Employee WHERE (HireDate BETWEEN ? AND ?) Moving on now to the Parameter Mapping tab this is where we are going to tell the task about our input paramaters. We Add them to the window specifying their direction and datatype. A quick word here about the structure of the variable name. As you can see SSIS has preceeded the variable with the word user. This is a default namespace for variables but you can create your own. When defining your variables if you look at the variables window title bar you will see some icons. If you hover over the last one on the right you will see it says "Choose Variable Columns". If you click the button you will see a list of checkbox options and one of them is namespace. after checking this you will see now where you can define your own namespace. The next tab, result set, is where we need to get back the value(s) returned from our statement and assign to a variable which in our case is CountOfEmployees so we can use it later perhaps. Because we are only returning a single value then if you remember from earlier we are allowed to assign a name to the resultset but it must be the name of the column (or alias) from the query. A really cool feature of Business Intelligence Studio being hosted by Visual Studio is that we get breakpoint support for free. In our package we set a Breakpoint so we can break the package and have a look in a watch window at the variable values as they appear to our task and what the variable value of our resultset is after the task has done the assignment. Here's that window now. As you can see the count of employess that matched the data range was 2. Returning a Rowset In this example we are going to return a resultset back to a variable after the task has executed not just a single row single value. There are no input parameters required so the variables window is nice and straight forward. One variable of type object. Here is the statement that will form the soure for our Resultset. select p.ProductNumber, p.name, pc.Name as ProductCategoryNameFROM Production.ProductCategory pcJOIN Production.ProductSubCategory pscON pc.ProductCategoryID = psc.ProductCategoryIDJOIN Production.Product pON psc.ProductSubCategoryID = p.ProductSubCategoryID We need to make sure that we have selected Full result set as the ResultSet as shown below on the task's General tab. Because there are no input parameters we can skip the parameter mapping tab and move straight to the Result Set tab. Here we need to Add our variable defined earlier and map it to the result name of 0 (remember we covered this earlier) Once we run the task we can again set a breakpoint and have a look at the values coming back from the task. In the following graphic you can see the result set returned to us as a COM object. We can do some pretty interesting things with this COM object and in later articles that is exactly what we shall be doing. Return Values, Input/Output Parameters and Returning a Rowset from a Stored Procedure This example is pretty much going to give us a taste of everything. We have already covered in the previous example how to specify the ResultSet to be a Full result set so we will not cover it again here. For this example we are going to need 4 variables. One for the return value, one for the input parameter, one for the output parameter and one for the result set. Here is the statement we want to execute. Note how much cleaner it is than if you wanted to do it using the current version of DTS. In the Parameter Mapping tab we are going to Add our variables and specify their direction and datatypes. In the Result Set tab we can now map our final variable to the rowset returned from the stored procedure. It really is as simple as that and we were amazed at how much easier it is than in DTS 2000. Passing in the SQL Statement from a Variable SSIS as we have mentioned is hugely more flexible than its predecessor and one of the things you will notice when moving around the tasks and the adapters is that a lot of them accept a variable as an input for something they need. The ExecuteSQL task is no different. It will allow us to pass in a string variable as the SQL Statement. This variable value could have been set earlier on from inside the package or it could have been populated from outside using a configuration. The ResultSet property is set to single row and we'll show you why in a second when we look at the variables. Note also the SQLSourceType property. Here's the General Tab again. Looking at the variable we have in this package you can see we have only two. One for the return value from the statement and one which is obviously for the statement itself. Again we need to map the Result name to our variable and this can be a named Result Name (The column name or alias returned by the query) and not 0. The expected result into our variable should be the amount of rows in the Person.Contact table and if we look in the watch window we see that it is.   Passing in the SQL Statement from a File The final example we are going to show is a really interesting one. We are going to pass in the SQL statement to the task by using a file connection manager. The file itself contains the statement to run. The first thing we are going to need to do is create our file connection mananger to point to our file. Click in the connections tray at the bottom of the designer, right click and choose "New File Connection" As you can see in the graphic below we have chosen to use an existing file and have passed in the name as well. Have a look around at the other "Usage Type" values available whilst you are here. Having set that up we can now see in the connection manager tray our file connection manager sitting alongside our OLE-DB connection we have been using for the rest of these examples. Now we can go back to the familiar General Tab to set up how the task will accept our file connection as the source. All the other properties in this task are set up exactly as we have been doing for other examples depending on the options chosen so we will not cover them again here.   We hope you will agree that the Execute SQL Task has changed considerably in this release from its DTS predecessor. It has a lot of options available but once you have configured it a few times you get to learn what needs to go where. We hope you have found this article useful.

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  • Interview with Al-Sorayai Group’s Managing Director on the Oracle Retail deployment

    - by user801960
    Recently, I had the opportunity to speak with Sheik Al Sorayai, Managing Director of the Saudi Arabian carpet and rug manufacturer, the Al-Sorayai Group. His business has recently implemented Oracle® Retail Merchandising and Stores applications in only six months to support the launch of its new furniture retail concept, HomeStyle. With an aggressive growth strategy for the new business in place, the Oracle Retail solutions are enabling Al-Sorayai to coordinate merchandising and store operations and improve decision-making and insight to optimise margins, reduce inventory costs and provide a consistent customer experience.

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  • SQL Server 2012 Memory Manager KB articles

    - by SQLOS Team
    Since the release of SQL Server 2012 with a redesigned memory manager, a steady stream of KB articles have been produced by CSS to provide guidance on the new or changed options, as well as fixes that have been published..   How has memory sizing changed in SQL 2012? 2663912 Memory configuration and sizing considerations in SQL Server 2012 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2663912     Setting "locked pages" to avoid SQL Server memory pages getting swapped has been simplified, particularly for Standard Edition, the details can be found here: 2659143 How to enable the "locked pages" feature in SQL Server 2012 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2659143   Note the following deprecation (particularly relevant for 32-bit installations): 2644592 The "AWE enabled" SQL Server feature is deprecated - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2644592   Note the following fixes available: 2708594 FIX: Locked page allocations are enabled without any warning after you upgrade to SQL Server 2012 - http://support.microsoft.com/kb/2708594/EN-US 2688697 FIX: Out-of-memory error when you run an instance of SQL Server 2012 on a computer that uses NUMA - http://support.microsoft.com/kb/2688697/EN-US Originally posted at http://blogs.msdn.com/b/sqlosteam/

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  • Java EE 7 interview @ InfoQ

    - by alexismp
    Anil Gaur, the head of JavaEE and GlassFish at Oracle, was recently interviewed by InfoQ on the progress and scope of Java EE 7. Make sure you read this for an up-to-date status. It turns out that the final release of Java EE 7 in now slated for late Q1, early Q2, 2013 with most specs expected t be at the Public Review stage by this summer. In addition to the improvements to the JMS, JAX-RS, JPA and JSF specifications Anil also covers the new JSON and WebSockets JSRs and gives a complete overview of the Java EE platform at it is shaping up with PaaS as its main theme.

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  • WebLogic history an interview with Laurie Pitman by Qualogy

    - by JuergenKress
    All those years that I am working with WebLogic, the BEA and Oracle era are the most well known about WebLogic evolving into a worldwide Enterprise platform for Java applications, being used by multinationals around the globe. But how did it all begin? Besides from the spare info you find on some Internet pages, I was eager to hear it in person from one of the founders of WebLogic back in 1995, before the BEA era, Laurie Pitman. Four young people, Carl Resnikoff, Paul Ambrose, Bob Pasker, and Laurie Pitman, became friends and colleagues about the time of the first release of Java in 1995. Between the four of them, they had an MA in American history, an MA in piano, an MS in library systems, a BS in chemistry, and a BS in computer science. They had come together kind of serendipitously, interested in building some web tools exclusively in Java for the emerging Internet web application market. They found many things to like about each other, some overlap in our interests, but also a lot of well-placed differences which made a partnership particularly interesting. They made it formal in January 1996 by incorporating. Read the complete article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: WebLogic history,Qualogy,WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

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  • The Retail Week Conference 2012 - Interview with Paul Dickson

    - by user801960
    Recently we attended the Retail Week Conference at the Hilton London Metropole Hotel in London. The conference proves to be an inspirational meeting of retail minds and the insight gained from both the speakers and the other delegates is invaluable. In particular we enjoyed hearing from Charlie Mayfield, Chairman at John Lewis Partnership, about understanding how the consumer is viewing the ever changing world of retail; a session on how to encourage brand-loyal multichannel activities from Robin Terrell of House of Fraser with Alan White of the N Brown Group, Vince Russell from The Cloud and Lucy Neville-Rolfe from Tesco; and a fascinating session from Tim Steiner, Chief Executive of Ocado, about how the business makes it as easy as possible for consumers to shop on their various platforms, which included some surprising usage statistics. Oracle's own Vice President of Retail, Paul Dickson, also held a session with Richard Pennycook, Group Finance Director at Morrisons, about the role of technology in accelerating and supporting the business strategy. Morrisons' 'Evolve' programme takes a litte-and-often approach to updating its technology infrastructure to spread cost and keep the adoption process gentle for staff, and the session explored how the process works and how Oracle's technology underpins the programme to optimise their operations using actionable insight. We had a quick chat with Paul Dickson at the session to get his thoughts on the programme - the video is below. We also filmed the whole presentation, so keep checking back on this blog if you're interested in seeing it.

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  • SQL Server 2012 Memory Manager KB articles

    - by SQLOS Team
    Since the release of SQL Server 2012 with a redesigned memory manager, a steady stream of KB articles have been produced by CSS to provide guidance on the new or changed options, as well as fixes that have been published..   How has memory sizing changed in SQL 2012? 2663912 Memory configuration and sizing considerations in SQL Server 2012 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2663912     Setting "locked pages" to avoid SQL Server memory pages getting swapped has been simplified, particularly for Standard Edition, the details can be found here: 2659143 How to enable the "locked pages" feature in SQL Server 2012 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2659143   Note the following deprecation (particularly relevant for 32-bit installations): 2644592 The "AWE enabled" SQL Server feature is deprecated - http://support.microsoft.com/default.aspx?scid=kb;EN-US;2644592   Note the following fixes available: 2708594 FIX: Locked page allocations are enabled without any warning after you upgrade to SQL Server 2012 - http://support.microsoft.com/kb/2708594/EN-US 2688697 FIX: Out-of-memory error when you run an instance of SQL Server 2012 on a computer that uses NUMA - http://support.microsoft.com/kb/2688697/EN-US Originally posted at http://blogs.msdn.com/b/sqlosteam/

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  • How do I make complex SQL queries easier to write?

    - by DragonLord
    I'm finding it very difficult to write complex SQL queries involving joins across many (at least 3-4) tables and involving several nested conditions. The queries I'm being asked to write are easily described by a few sentences, but can require a deceptive amount of code to complete. I'm finding myself often using temporary views to write these queries, which seem like a bit of a crutch. What tips can you provide that I can use to make these complex queries easier? More specifically, how do I break these queries down into the steps I need to use to actually write the SQL code? Note that I'm the SQL I'm being asked to write is part of homework assignments for a database course, so I don't want software that will do the work for me. I want to actually understand the code I'm writing. More technical details: The database is hosted on a PostgreSQL server running on the local machine. The database is very small: there are no more than seven tables and the largest table has less than about 50 rows. The SQL queries are being passed unchanged to the server, via LibreOffice Base.

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  • My Interview With DevExpress Regarding Silicon Valley Code Camp

    Last week, while at Microsofts TechEd 2010, Mehul Harry, Technical Evangalist for Developer Express, interviewed me about our upcoming Silicon Valley Code Camp (of which Dev Express is a platinum... This site is a resource for asp.net web programming. It has examples by Peter Kellner of techniques for high performance programming...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Questions about Mac Book Pro Keyboard and shortcuts

    - by SimonSolnes
    I have been researching a lot about this and I cannot seem to find any useful information about this topic, what so ever. I have now been using Ubuntu in one week, and have gotten pretty confident with almost everything. Except keyboard layout and shortcuts. If you know a tutorial or a documents explaining keyboard shortcuts in Ubuntu or linux in general, can you please list it? I use a Mac Book Pro with a Norwegian keyboard, and I have several questions about this: Is there a program for having a consise list of absolutely all keyboard shortcuts, and be able to change them? How do I use my fn keys? (fn button doesnt do the job for some reason) How can I use my alt+letter-key-or-number-key or alt+shift+letter-key-or-number-key to get fancy characters. (Like I do on Mac OS X) How can I swap cmd and ctrl key system wide? Also I really want to be oriented around this subject, since this is the only thing holding me back on Ubuntu, so if there exists some in-depth material on this, it would be great. Also, if there exists some programs or material out there making it easier with Mac hardware I would enjoy that. Sorry if my questions seems vague. Thank you very much Simon

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  • Interview

    Duncan Mills, senior director of product management at Oracle, talks about the recent release of Oracle Enterprise Pack for Eclipse 11g.

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  • Interview

    OTN's Justin Kestelyn talks with Richard Sarwal and Leng Leng Tan of Oracle product development about Oracle Enterprise Manager 10g Release 5.

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  • "Interview"

    Thomas Kurian, senior vice president, Oracle Fusion Middleware, talks about Oracle’s acquisition of BEA.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

    Read the article

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