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  • Good resource for studying Database High Availability techniques

    - by Invincible
    Hello Can anybody suggest some good resource/book on Database high availability techniques? Moreover, High-availability of system software like Intrusion Prevention system or Web servers. I am considering high-availability is global term which covers clustring, cloud computing, replication, replica management, distributed synchronization for cluster. Thanks in advance!

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  • Database Design Question

    - by Soo
    Ok SO, I have a user table and want to define groups of users together. The best solution I have for this is to create three database tables as follows: UserTable user_id user_name UserGroupLink group_id member_id GroupInfo group_id group_name This method keeps the member and group information separate. This is just my way of thinking. Is there a better way to do this? Also, what is a good naming convention for tables that link two other tables?

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  • What should every developer know about databases?

    - by Aaronaught
    Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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  • SQL SERVER – FIX : ERROR : 4214 BACKUP LOG cannot be performed because there is no current database

    - by pinaldave
    I recently got following email from one of the reader. Hi Pinal, Even thought my database is in full recovery mode when I try to take log backup I am getting following error. BACKUP LOG cannot be performed because there is no current database backup. (Microsoft.SqlServer.Smo) How to fix it? Thanks, [name and email removed as requested] Solution / Fix: This error can happen when you have never taken full backup of your database and you try to attempt to take backup of the log only. Take full backup once and attempt to take log back up. If the name of your database is MyTestDB follow procedure as following. BACKUP DATABASE [MyTestDB] TO DISK = N'C:\MyTestDB.bak' GO BACKUP LOG [MyTestDB] TO DISK = N'C:\MyTestDB.bak' GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Backup and Restore, SQL Error Messages, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Log

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  • CakePHP Missing Database Table Error

    - by BRADINO
    I am baking a new project management application at work and added a couple new tables to the database today. When I went into the console to bake the new models, they were not in the list... php /path/cake/console/cake.php bake all -app /path/app/ So I manually typed in the model name and I got a missing database table for model error. I checked and double-checked and the database table was named properly. Turns out that some files inside the /app/tmp/cache/ folder were causing Cake not to recognize that I had added new tables to my database. Once I deleted the cache files cake instantly recognized my new database tables and I was baking away! rm -Rf /path/app/tmp/cache/cake*

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  • PHP OCI8 and Oracle 11g DRCP Connection Pooling in Pictures

    - by christopher.jones
    Here is a screen shot from a PHP OCI8 connection pooling demo that I like to run. It graphically shows how little database host memory is needed when using DRCP connection pooling with Oracle Database 11g. Migrating to DRCP can be as simple as starting the pool and changing the connection string in your PHP application. The script that generated the data for this graph was a simple "Parts" query application being run under various simulated user loads. I was running the database on a small Oracle Linux server with just 2G of memory. I used PHP OCI8 1.4. Apache is in pre-fork mode, as needed for PHP. Each graph has time on the horizontal access in arbitrary 'tick' time units. Click the image to see it full sized. Pooled connections Beginning with the top left graph, At tick time 65 I used Apache's 'ab' tool to start 100 concurrent 'users' running the application. These users connected to the database using DRCP: $c = oci_pconnect('phpdemo', 'welcome', 'myhost/orcl:pooled'); A second hundred DRCP users were added to the system at tick 80 and a final hundred users added at tick 100. At about tick 110 I stopped the test and restarted Apache. This closed all the connections. The bottom left graph shows the number of statements being executed by the database per second, with some spikes for background database activity and some variability for this small test. Each extra batch of users adds another 'step' of load to the system. Looking at the top right Server Process graph shows the database server processes doing the query work for each web user. As user load is added, the DRCP server pool increases (in green). The pool is initially at its default size 4 and quickly ramps up to about (I'm guessing) 35. At tick time 100 the pool increases to my configured maximum of 40 processes. Those 40 processes are doing the query work for all 300 web users. When I stopped the test at tick 110, the pooled processes remained open waiting for more users to connect. If I had left the test quiet for the DRCP 'inactivity_timeout' period (300 seconds by default), the pool would have shrunk back to 4 processes. Looking at the bottom right, you can see the amount of memory being consumed by the database. During the initial quiet period about 500M of memory was in use. The absolute number is just an indication of my particular DB configuration. As the number of pooled processes increases, each process needs more memory. You can see the shape of the memory graph echoes the Server Process graph above it. Each of the 300 web users will also need a few kilobytes but this is almost too small to see on the graph. Non-pooled connections Compare the DRCP case with using 'dedicated server' processes. At tick 140 I started 100 web users who did not use pooled connections: $c = oci_pconnect('phpdemo', 'welcome', 'myhost/orcl'); This connection string change is the only difference between the two tests. At ticks 155 and 165 I started two more batches of 100 simulated users each. At about tick 195 I stopped the user load but left Apache running. Apache then gradually returned to its quiescent state, killing idle httpd processes and producing the downward slope at the right of the graphs as the persistent database connection in each Apache process was closed. The Executions per Second graph on the bottom left shows the same step increases as for the earlier DRCP case. The database is handling this load. But look at the number of Server processes on the top right graph. There is now a one-to-one correspondence between Apache/PHP processes and DB server processes. Each PHP processes has one DB server processes dedicated to it. Hence the term 'dedicated server'. The memory required on the database is proportional to all those database server processes started. Almost all my system's memory was consumed. I doubt it would have coped with any more user load. Summary Oracle Database 11g DRCP connection pooling significantly reduces database host memory requirements allow more system memory to be allocated for the SGA and allowing the system to scale to handled thousands of concurrent PHP users. Even for small systems, using DRCP allows more web users to be active. More information about PHP and DRCP can be found in the PHP Scalability and High Availability chapter of The Underground PHP and Oracle Manual.

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  • I love programming but never get projects started

    - by 0xHenry
    I read this question and the most voted answer and said to myself "Those things are what I want to do! But why the heck I'm not doing it?" The problem here is that I can't get anything started. I hope you get some kind of idea what I'm interested in and can help me continue programming. I'm interested in embedded programming and I'd like to learn some ARM assembly. I think those could be combined with image processing. Also I'd love to create programs that are actually useful to some people but it seems like there are already multiple programs for pretty much every purpose. Maybe if I found an interesting program without open source alternatives I could get a great project to work on. How could I get myself to finally start a project or few and keep myself interested in them? I just want to get myself to do something I love.

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  • Mathematica Programming Language&ndash;An Introduction

    - by JoshReuben
    The Mathematica http://www.wolfram.com/mathematica/ programming model consists of a kernel computation engine (or grid of such engines) and a front-end of notebook instances that communicate with the kernel throughout a session. The programming model of Mathematica is incredibly rich & powerful – besides numeric calculations, it supports symbols (eg Pi, I, E) and control flow logic.   obviously I could use this as a simple calculator: 5 * 10 --> 50 but this language is much more than that!   for example, I could use control flow logic & setup a simple infinite loop: x=1; While [x>0, x=x,x+1] Different brackets have different purposes: square brackets for function arguments:  Cos[x] round brackets for grouping: (1+2)*3 curly brackets for lists: {1,2,3,4} The power of Mathematica (as opposed to say Matlab) is that it gives exact symbolic answers instead of a rounded numeric approximation (unless you request it):   Mathematica lets you define scoped variables (symbols): a=1; b=2; c=a+b --> 5 these variables can contain symbolic values – you can think of these as partially computed functions:   use Clear[x] or Remove[x] to zero or dereference a variable.   To compute a numerical approximation to n significant digits (default n=6), use N[x,n] or the //N prefix: Pi //N -->3.14159 N[Pi,50] --> 3.1415926535897932384626433832795028841971693993751 The kernel uses % to reference the lastcalculation result, %% the 2nd last, %%% the 3rd last etc –> clearer statements: eg instead of: Sqrt[Pi+Sqrt[Sqrt[Pi+Sqrt[Pi]]] do: Sqrt[Pi]; Sqrt[Pi+%]; Sqrt[Pi+%] The help system supports wildcards, so I can search for functions like so: ?Inv* Mathematica supports some very powerful programming constructs and a rich function library that allow you to do things that you would have to write allot of code for in a language like C++.   the Factor function – factorization: Factor[x^3 – 6*x^2 +11x – 6] --> (-3+x) (-2+x) (-1+x)   the Solve function – find the roots of an equation: Solve[x^3 – 2x + 1 == 0] -->   the Expand function – express (1+x)^10 in polynomial form: Expand[(1+x)^10] --> 1+10x+45x^2+120x^3+210x^4+252x^5+210x^6+120x^7+45x^8+10x^9+x^10 the Prime function – what is the 1000th prime? Prime[1000] -->7919 Mathematica also has some powerful graphics capabilities:   the Plot function – plot the graph of y=Sin x in a single period: Plot[Sin[x], {x,0,2*Pi}] you can also plot 3D surfaces of functions using Plot3D function

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  • unix systems programming jobs in India [closed]

    - by mnunna
    Hi, I am currently working on a HP-UX platform and my role as a prod support team member involves mostly to write shell scripts. But i want to branch out into core systems programming in unix. A quick search on the internet threw no "unix systems programming jobs" in india. I'm confused as what to do. I really would like to continue with unix as my core competency, but unix jobs in india are mostly of sys admin/ prod support type, of which i do not want a part of. Can anyone of you give me an informed advice on the career oppurtinities that await unix professionals in india?? Any advice would be appreciated.

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  • Does programming knowledge have a half-life?

    - by Gary Rowe
    In answering this question, I asserted that programming knowledge has a half-life of about 18 months. In physics, we have radioactive decay which is the process by which a radioactive element transforms into something less energetic. The half-life is the measure of how long it takes for this process to result in only half of the material to remain. A parallel concept might be that over time our programming knowledge ceases to be the current idiom and eventually becomes irrelevant. Noting that a half-life is asymptotic (so some knowledge will always be relevant), what are your thoughts on this? Is 18 months a good estimate? Is it even the case? Does it apply to design patterns, but over a longer period? What are the inherent advantages/disadvantages of this half-life? Update Just found this question which covers the material fairly well: "Half of everything you know will be obsolete in 18-24 months" = ( True, or False? )

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  • QotD: Peter Wayner on Programming trend No. 1

    - by $utils.escapeXML($entry.author)
    Programming trend No. 1: The JVM is not just for Java anymoreA long time ago, Sun created Java and shared the virtual machine with the world. By the time Microsoft created C#, people recognized that the VM didn't have to be limited to one language. Anything that could be transformed into the byte code could use it.Now, it seems that everyone is building their language to do just that. Leave the job of building a virtual machine to Sun/Oracle, and concentrate your efforts on the syntactic bells and structural whistles, goes the mantra today.Peter Wayner in an article on "11 programming trends to watch" at ITWorld.

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  • 'Other' Features in a programming language

    - by user12960
    Online (i cant remember where) i saw someone mention he wishes programming language has more built in features for tools like documentation and source control. Now i dont understand what needs to be built in for source control since tools like git (sorry but i dont have much experience with others) has everything i need and is very easy to use. Documentation i can understand, perhaps the ability to generate remote procedures calls from source to some kind of IDL would be cool. But really i dont understand what features a programming language can/should have that isnt tied with code generation and syntax (except the two i mention when it comes to libraries). What ideas do you guys have? What is your wishlist?

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  • Apache cannot find mysql database modules

    - by user809857
    I've created a simple django project and setup a mysql database. My simple project just creates an entry on the database. The project works fine when I use the built in development server provided by django (runserver) and it works well. But when I deployed the project on Apache and mod_Wsgi (Ubuntu server), django could not find 'books', which is in this case my table in the database. The mysql database that I use in runserver and apache are just the same. I also did rebuild the database using sqlall,validate and syncdb of django but still i get the error. What could be wrong with what I'm doing? Thanks

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  • Practical Meta Programming System (MPS)

    - by INTPnerd
    This is in regards to Meta Programming System or MPS by JetBrains. Thus far, from my efforts to learn how to use MPS, I have only learned its basic purpose and that it is very complex. Is MPS worth learning? Is there anyone who already effectively uses MPS to create their own languages and editors for those languages and uses these created editors as their primary way of programming? If so, what types of programs have they made with this? What are the advantages and disadvantages of working with MPS? What is the best way to learn MPS?

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  • Outdoor Programming Jobs...

    - by Rodrick Chapman
    Are there any kinds of jobs that require programming (or at least competency) but take place outdoors for a significant portion of the time? As long as I'm fantasizing, an ideal job would involve programming in a high level language like Haskell, F#, or Scala* for, say, 50% of the time and doing something like digging an irrigation trench the rest of the time. My background: I triple majored in mathematics, philosophy, and history (BS/BA) and have been working as a web developer for the past six years. I love hacking but I'm feeling a bit burned out. *I only chose these languages as examples since, ideally, I'd want to work among high caliber people... but it really doesn't matter.

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  • Apache cannot find mysql database modules

    - by user809857
    I've created a simple django project and setup a mysql database. My simple project just creates an entry on the database. The project works fine when I use the built in development server provided by django (runserver) and it works well. But when I deployed the project on Apache and mod_Wsgi (Ubuntu server), django could not find 'books', which is in this case my table in the database. The mysql database that I use in runserver and apache are just the same. I also did rebuild the database using sqlall,validate and syncdb of django but still i get the error. What could be wrong with what I'm doing? Thanks

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  • Oracle Database 12c

    - by jgelhaus
    What's your pain? Cost of IT and downtime, Complexity of IT, Poor database application performance? All of the above and more? These are real challenges caused by today's demands on data centers and their IT teams.  Oracle Database 12c provides a breakthrough architecture that makes it easy to deploy and manage databases in the cloud. Oracle partners will leverage Database 12c innovation to provide additional options for Oracle customer success and ROI. Download Oracle Database 12c and plug into the cloud! Join us for our July 10th webcast to learn about this database breakthrough.

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  • Most underestimated programming tool

    - by Anto
    We have many great tools which helps a lot when programming, such as good programmers text editors, IDEs, debuggers, version control systems etc. Some of the tools are more or less "must have" tools for getting the job done (e.g. compilers). There are still always tools which do help a lot, but still don't get so much attention, for various reasons, for instance, when they were released, they were ahead of their time and now are more or less forgotten. What type of programming tool do you think is the most underestimated one? Motivate your answer.

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  • Goto for the Java Programming Language

    - by darcy
    Work on JDK 8 is well-underway, but we thought this late-breaking JEP for another language change for the platform couldn't wait another day before being published. Title: Goto for the Java Programming Language Author: Joseph D. Darcy Organization: Oracle. Created: 2012/04/01 Type: Feature State: Funded Exposure: Open Component: core/lang Scope: SE JSR: 901 MR Discussion: compiler dash dev at openjdk dot java dot net Start: 2012/Q2 Effort: XS Duration: S Template: 1.0 Reviewed-by: Duke Endorsed-by: Edsger Dijkstra Funded-by: Blue Sun Corporation Summary Provide the benefits of the time-testing goto control structure to Java programs. The Java language has a history of adding new control structures over time, the assert statement in 1.4, the enhanced for-loop in 1.5,and try-with-resources in 7. Having support for goto is long-overdue and simple to implement since the JVM already has goto instructions. Success Metrics The goto statement will allow inefficient and verbose recursive algorithms and explicit loops to be replaced with more compact code. The effort will be a success if at least twenty five percent of the JDK's explicit loops are replaced with goto's. Coordination with IDE vendors is expected to help facilitate this goal. Motivation The goto construct offers numerous benefits to the Java platform, from increased expressiveness, to more compact code, to providing new programming paradigms to appeal to a broader demographic. In JDK 8, there is a renewed focus on using the Java platform on embedded devices with more modest resources than desktop or server environments. In such contexts, static and dynamic memory footprint is a concern. One significant component of footprint is the code attribute of class files and certain classes of important algorithms can be expressed more compactly using goto than using other constructs, saving footprint. For example, to implement state machines recursively, some parties have asked for the JVM to support tail calls, that is, to perform a complex transformation with security implications to turn a method call into a goto. Such complicated machinery should not be assumed for an embedded context. A better solution is just to expose to the programmer the desired functionality, goto. The web has familiarized users with a model of traversing links among different HTML pages in a free-form fashion with some state being maintained on the side, such as login credentials, to effect behavior. This is exactly the programming model of goto and code. While in the past this has been derided as leading to "spaghetti code," spaghetti is a tasty and nutritious meal for programmers, unlike quiche. The invokedynamic instruction added by JSR 292 exposes the JVM's linkage operation to programmers. This is a low-level operation that can be leveraged by sophisticated programmers. Likewise, goto is a also a low-level operation that should not be hidden from programmers who can use more efficient idioms. Some may object that goto was consciously excluded from the original design of Java as one of the removed feature from C and C++. However, the designers of the Java programming languages have revisited these removals before. The enum construct was also left out only to be added in JDK 5 and multiple inheritance was left out, only to be added back by the virtual extension method methods of Project Lambda. As a living language, the needs of the growing Java community today should be used to judge what features are needed in the platform tomorrow; the language should not be forever bound by the decisions of the past. Description From its initial version, the JVM has had two instructions for unconditional transfer of control within a method, goto (0xa7) and goto_w (0xc8). The goto_w instruction is used for larger jumps. All versions of the Java language have supported labeled statements; however, only the break and continue statements were able to specify a particular label as a target with the onerous restriction that the label must be lexically enclosing. The grammar addition for the goto statement is: GotoStatement: goto Identifier ; The new goto statement similar to break except that the target label can be anywhere inside the method and the identifier is mandatory. The compiler simply translates the goto statement into one of the JVM goto instructions targeting the right offset in the method. Therefore, adding the goto statement to the platform is only a small effort since existing compiler and JVM functionality is reused. Other language changes to support goto include obvious updates to definite assignment analysis, reachability analysis, and exception analysis. Possible future extensions include a computed goto as found in gcc, which would replace the identifier in the goto statement with an expression having the type of a label. Testing Since goto will be implemented using largely existing facilities, only light levels of testing are needed. Impact Compatibility: Since goto is already a keyword, there are no source compatibility implications. Performance/scalability: Performance will improve with more compact code. JVMs already need to handle irreducible flow graphs since goto is a VM instruction.

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  • How should calculations be handled in a document database

    - by Morten
    Ok, so I have a program that basically logs errors into a nosql database. Right now there is just a single model for an error and its stored as a document in the nosql database. Basically I want to summarize across different errors and produce a summary of the "types" of errors that occured. Traditionally in a SQL database the this normalization would work with groupings, sums and averages but in a NoSQL database I assume I need to use mapreduce. My current model seems unfit for the task, how should I change the way I store "models" in order to make statistical analysis easy? Would a NoSQL database even be the right tool for this type of problem? I'm storing things in Google AppEngine's BigTable, so there are some limitations to think of as well.

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  • Stagnating in programming

    - by Coder
    Time after time this question came up in my mind, but up until today I wasn't thinking about it much. I have been programming for maybe around 8 years now, and for the last two years it seems I'm not as keen to pick up new technologies anymore. Maybe that's a burnout or something, but I'd say it's experience and what I like, that's stopping me from running after the latest and greatest. I'm C++ developer, by this I mean, I love close to metal programming. I have no problems tracing problems through assembly, using tools like WinDbg or HexView. When I use constructs, I think about how they are realized underneath, how the bits are set and unset under the hood. I love battling with complex threading problems and doing everything hardcore way, even by hand if the regular solutions seem half baked. But I also love the C++0x stuff, and use it a lot. And all C++ code as long as it's not cumbersome compared to C counterparts, sometimes I also fall back to sort of "Super C" if the C++ way is ugly. And then there are all other developers who seem to be way more forward looking, .Net 4.0 MVC, WPF, all those Microsoft X#s, LINQ languages, XML and XSLT, mobile devices and so on. I have done a considerable amount of .NET, SQL, ASPX programming, but the further I go, the less I want to try those technologies. Is that bad? Almost every day I hear people saying that managed code is the only way forward, WPF is the way to go. I hear that C++ is godawful, and you can't code anything in it that's somewhat stable. But I don't buy it. With the experience I have, and the knowledge of how native code is compiled and executes, I can say I find it extremely rare that C++ code is unstable, or leaks, or causes crashes that takes more than 30 seconds to identify and fix. And to tell the truth, I've seen enough problems with other "cool" languages that I'd say C++ is even more stable and production proof than the safe languages, at least for me. The only thing that scares me in C++ is new frameworks, I don't trust them, and I use them extra sparingly. STL - yes, ATL - very sparingly, everything else... Well, not very keen on it. Most huge problems I've ran into, all were related to frameworks, not the language itself. Some overrided operator here, bad hierarchy there, poor class design here, mystical castings there. Other than that, C/C++ (yes, I use them together) still seems a very controlled and stable way to develop applications. Am I stagnating? Should I switch a profession, or force myself in all that marketing hype? Are there more developers who feel the same way?

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  • Object Oriented programming on 8-bit MCU Case Study

    - by Calvin Grier
    I see that there's a lot of questions related to OO Programming here. I'm actually trying to find a specific resource related to embedded OO approaches for an 8 bit MCU. Several years back (maybe 6) I was looking for material related to Object Oriented programming for resource constrained 8051 microprocessors. I found an article/website with a case history of a design group that used a very small RAM part, and implemented many Object based constructs during their C design and development. I believe it was an 8051. The project was a success, and managed to stay inside the very small ROM/RAM they had available. I'm attempting to find it again, but Google can't locate it. The article was well written, and recommended a "mixed" approach using C methods for inheritance and encapsulation - if I recall correctly. Can anyone help me locate this article?

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  • Lower Your Application Infrastructure Costs w/Oracle Database 11g

    - by john.brust
    Oracle Database 11g is designed to support enterprise applications, including Oracle E-Business Suite, Oracle PeopleSoft, and Oracle Siebel. And every Oracle customer can benefit from the performance, reliability, and security that Oracle Database 11g brings to these applications. Plus, Oracle Database 11g, helps you drive down your IT infrastructure costs. Join us next Friday for a webcast conversation with database expert Mark Townsend, Vice President of Oracle's Server Technology Division, to learn how you can benefit from running your applications on Oracle Database 11g. At the end of the presentation, we'll open up for live Q&A for approximately 30 minutes. Register now for our Friday, April 23rd, 2010 9:30am PT | 12:30pm ET live webcast.

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