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  • Online games programming basics

    - by Renkon
    I am writing with regard to an issue I am having nowadays. I have come up with an interesting idea of making an online game in C#, yet I do not have the knowledge to work with more than a player. Basic games like a TIC-TAC-TOE or a SNAKE were done already, and I would like to do a simple, but online, game. Would you mind giving me some tutorials or guides related to that? I would really like to learn how to work online with the client/server structure (though, I do know the basics about that structure). I look forward to reading from you. Yours faithfully, Renkon.

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  • Resources needed: basics of using make/qmake

    - by Mikey
    I am look for a good book or website that clearly explains the basics of using make, (particularly qmake for Qt development) makefiles, etc. for building C++/Qt executables. I am using open source tools on Ubuntu. Lately have been doing a lot of Qt/C++ development using the CodeLite IDE, which works quite well with Qt, however when I wanted to write my own QObject derivatives with custom signal and slots, I discovered I had to use qmake and I don't know how. (Meanwhile I have been using QtCreator, which handles this, but it not my IDE of choice) I have several books on C++ and Qt but I haven't found that they focus at all on this area. Recommendations please...

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  • Jump into Android or learn Java basics first?

    - by daniels
    I am quite proficient in C and know some C++, but never touched Java. Recently I got an idea for an app which I think has potential, and I want to develop it. I am planning to go Android first, cause it doesn't require a mac/iPhone. So my question is: can I go straight to learning Android development, picking up the Java syntax as I go along and need it (after all I don't think it's much different from C/C++), or should I take a couple of weeks to learn the basics of Java first and then start with Android development?

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  • SQL Injection – Beyond the Basics - A good article

    - by TATWORTH
    At http://www.sqlmag.com/content1/topic/sql-injection-basics-142364/catpath/sql-server/utm_source/feedburner/utm_medium/feed, there is an excellent article on the measures needed to defeat SQL Injection Attack. Read the article but also remember that the account the application uses to access the database adhere to the following points:NEVER EVER use the sa account even in development.Route access via a role on the database.The account should have the minimum privilege required for the job.The account should have no access whatsoever to any other database not required by the application.If you can avoid mixed mode authentication do so and grant access via to a windows group to which you add users.

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  • SSIS Basics: Using the Execute SQL Task to Generate Result Sets

    The Execute SQL Task of SSIS is extraordinarily useful, but it can cause a lot of difficulty for developers learning SSIS, or only using it occasionally. What it needed, we felt, was a clear step-by-step guide that showed the basics of how to use it effectively. Annette Allen has once again cleared the fog of confusion. NEW! Take the stress out of .NET deploymentEliminate the risk in deploying manually to live systems using Deployment Manager, the new tool from Red Gate. Try it now.

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  • browser back acts on nested iframe before the page itself - is there a way to avoid it??

    - by kfiroo
    hi, i have a page with dynamic data loaded by some ajax and lots of javascript. the page contains a list from which the user can choose and each selected value loads new data to the page. one of these data items is a url provided to an iframe. i use jQuery BBQ: Back Button & Query Library to simulate the browser-back behavior. all works well besides the fact that when i click the back button for the first time the iframe goes back to its previous location and then i need to click back again to make the page go back. is there a way to disable the iframe's back behavior?

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  • SQL Server – Learning SQL Server Performance: Indexing Basics – Interview of Vinod Kumar by Pinal Dave

    - by pinaldave
    Recently I just wrote a blog post on about Learning SQL Server Performance: Indexing Basics and I received lots of request that if we can share some insight into the course. Every single time when Performance is discussed, Indexes are mentioned along with it. In recent times, data and application complexity is continuously growing.  The demand for faster query response, performance, and scalability by organizations is increasing and developers and DBAs need to now write efficient code to achieve this. When we developed the course – we made sure that this course remains practical and demo heavy instead of just theories on this subject. Vinod Kumar and myself we often thought about this and realized that practical understanding of the indexes is very important. One can not master every single aspects of the index. However there are some minimum expertise one should gain if performance is one of the concern. Here is 200 seconds interview of Vinod Kumar I took right after completing the course. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology, Video

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  • E-Business Suite - Cloning Basics & AMP Cloning - EMEA/APAC

    - by Annemarie Provisero
    ADVISOR WEBCAST: E-Business Suite - Cloning Basics & AMP Cloning - EMEA/APAC PRODUCT FAMILY: EBS – ATG - Utilities July 19, 2011 at 10:00 am CET, 01:30 pm India, 05:00 pm Japan, 06:00 pm Australia This 1.5-hour session is recommended for technical and functional Users who are interested to get an generic overview about the Cloning functionality available in the E-Business Suite Release. We are going to talk about the generic Cloning options and will then go into depth about the cloning scenario when using AMP (Applications Management Pack) within the Enterprise Manager. TOPICS WILL INCLUDE: Cloning Overview Rapidclone steps in Details Rapidclone limitations EM Grid Setup with AMP for Cloning Advantages of Cloning with AMP Cloning Procedures available with AMP Monitoring Clone Operation Few things to remember before Cloning A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. Click here to register for this session ------------------------------------------------------------------------------------------------------------- The above webcast is a service of the E-Business Suite Communities in My Oracle Support. For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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  • E-Business Suite - Cloning Basics & AMP Cloning - US

    - by Annemarie Provisero
    ADVISOR WEBCAST: E-Business Suite - Cloning Basics & AMP Cloning - US PRODUCT FAMILY: EBS – ATG - Utilities July 20, 2011 at 17:00 UK / 18:00 CET / 09:00 am Pacific / 10:00 am Mountain / 12:00 Eastern This 1.5-hour session is recommended for technical and functional Users who are interested to get an generic overview about the Cloning functionality available in the E-Business Suite Release. We are going to talk about the generic Cloning options and will then go into depth about the cloning scenario when using AMP (Applications Management Pack) within the Enterprise Manager. TOPICS WILL INCLUDE: Cloning Overview Rapidclone steps in Details Rapidclone limitations EM Grid Setup with AMP for Cloning Advantages of Cloning with AMP Cloning Procedures available with AMP Monitoring Clone Operation Few things to remember before Cloning A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. Click here to register for this session ------------------------------------------------------------------------------------------------------------- The above webcast is a service of the E-Business Suite Communities in My Oracle Support. For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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  • ZFS Basics

    - by user12614620
    Stage 1 basics: creating a pool # zpool create $NAME $REDUNDANCY $DISK1_0..N [$REDUNDANCY $DISK2_0..N]... $NAME = name of the pool you're creating. This will also be the name of the first filesystem and, by default, be placed at the mountpoint "/$NAME" $REDUNDANCY = either mirror or raidzN, and N can be 1, 2, or 3. If you leave N off, then it defaults to 1. $DISK1_0..N = the disks assigned to the pool. Example 1: zpool create tank mirror c4t1d0 c4t2d0 name of pool: tank redundancy: mirroring disks being mirrored: c4t1d0 and c4t2d0 Capacity: size of a single disk Example 2: zpool create tank raidz c4t1d0 c4t2d0 c4t3d0 c4t4d0 c4t5d0 Here the redundancy is raidz, and there are five disks, in a 4+1 (4 data, 1 parity) config. This means that the capacity is 4 times the disk size. If the command used "raidz2" instead, then the config would be 3+2. Likewise, "raidz3" would be a 2+3 config. Example 3: zpool create tank mirror c4t1d0 c4t2d0 mirror c4t3d0 c4t4d0 This is the same as the first mirror example, except there are two mirrors now. ZFS will stripe data across both mirrors, which means that writing data will go a bit faster. Note: you cannot create a mirror of two raidzs. You can create a raidz of mirrors, but to do that requires trickery.

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  • Software Error Basics

    Software Error Basics Who Causes Errors?   Software errors are caused by: ·    End-users ·    Programmers ·    Computer Systems   What Causes Errors?   Software errors are caused by: ·    Programmer Mistakes and Assumptions ·    Invalid data ·    Unexpected User Interactions ·    Missing Resources o  Files o  Databases o  Network Connectivity ·    Poor network connection ·    Insufficient Permissions   Where Do Errors Occur?   Software errors can occur anywhere code is executed:   ·    Desktop PC ·    Laptop PC ·    Server ·    Tablet PC ·    Mobile Phone ·    Any Device that can execute software   When Do Errors Occur?   Software errors occur when source code is being compiled (Compile-Time) or executed (Run-Time).  

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  • CouchDB basics for PHP developers

    <b>IBM Developerworks:</b> "If you're a typical PHP developer, it doesn't take a thorough review of past projects to pick out a telling pattern: In most (if not all) cases, you're probably getting PHP to talk to a database back end for all that dynamic data goodness; in 99 percent of those instances, you're using MySQL."

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  • SEO Services - Basics, Techniques and Value

    There are numerous SEO methods, which will actually out-do expectations. These methods are used for providing hits leading back to your site, yet reserving a reasonable ranking position. The simple explanation is that there is not a single SEO method guaranteeing instant success.

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  • Big Data – Basics of Big Data Architecture – Day 4 of 21

    - by Pinal Dave
    In yesterday’s blog post we understood how Big Data evolution happened. Today we will understand basics of the Big Data Architecture. Big Data Cycle Just like every other database related applications, bit data project have its development cycle. Though three Vs (link) for sure plays an important role in deciding the architecture of the Big Data projects. Just like every other project Big Data project also goes to similar phases of the data capturing, transforming, integrating, analyzing and building actionable reporting on the top of  the data. While the process looks almost same but due to the nature of the data the architecture is often totally different. Here are few of the question which everyone should ask before going ahead with Big Data architecture. Questions to Ask How big is your total database? What is your requirement of the reporting in terms of time – real time, semi real time or at frequent interval? How important is the data availability and what is the plan for disaster recovery? What are the plans for network and physical security of the data? What platform will be the driving force behind data and what are different service level agreements for the infrastructure? This are just basic questions but based on your application and business need you should come up with the custom list of the question to ask. As I mentioned earlier this question may look quite simple but the answer will not be simple. When we are talking about Big Data implementation there are many other important aspects which we have to consider when we decide to go for the architecture. Building Blocks of Big Data Architecture It is absolutely impossible to discuss and nail down the most optimal architecture for any Big Data Solution in a single blog post, however, we can discuss the basic building blocks of big data architecture. Here is the image which I have built to explain how the building blocks of the Big Data architecture works. Above image gives good overview of how in Big Data Architecture various components are associated with each other. In Big Data various different data sources are part of the architecture hence extract, transform and integration are one of the most essential layers of the architecture. Most of the data is stored in relational as well as non relational data marts and data warehousing solutions. As per the business need various data are processed as well converted to proper reports and visualizations for end users. Just like software the hardware is almost the most important part of the Big Data Architecture. In the big data architecture hardware infrastructure is extremely important and failure over instances as well as redundant physical infrastructure is usually implemented. NoSQL in Data Management NoSQL is a very famous buzz word and it really means Not Relational SQL or Not Only SQL. This is because in Big Data Architecture the data is in any format. It can be unstructured, relational or in any other format or from any other data source. To bring all the data together relational technology is not enough, hence new tools, architecture and other algorithms are invented which takes care of all the kind of data. This is collectively called NoSQL. Tomorrow Next four days we will answer the Buzz Words – Hadoop. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • int, short, byte performance in back-to-back for-loops

    - by runrunraygun
    (background: http://stackoverflow.com/questions/1097467/why-should-i-use-int-instead-of-a-byte-or-short-in-c) To satisfy my own curiosity about the pros and cons of using the "appropriate size" integer vs the "optimized" integer i wrote the following code which reinforced what I previously held true about int performance in .Net (and which is explained in the link above) which is that it is optimized for int performance rather than short or byte. DateTime t; long a, b, c; t = DateTime.Now; for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } a = DateTime.Now.Ticks - t.Ticks; t = DateTime.Now; for (short index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } b=DateTime.Now.Ticks - t.Ticks; t = DateTime.Now; for (byte index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } c=DateTime.Now.Ticks - t.Ticks; Console.WriteLine(a.ToString()); Console.WriteLine(b.ToString()); Console.WriteLine(c.ToString()); This gives roughly consistent results in the area of... ~950000 ~2000000 ~1700000 which is in line with what i would expect to see. However when I try repeating the loops for each data type like this... t = DateTime.Now; for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } for (int index = 0; index < 127; index++) { Console.WriteLine(index.ToString()); } a = DateTime.Now.Ticks - t.Ticks; the numbers are more like... ~4500000 ~3100000 ~300000 Which I find puzzling. Can anyone offer an explanation? NOTE: In the interest of compairing like for like i've limited the loops to 127 because of the range of the byte value type. Also this is an act of curiosity not production code micro-optimization.

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  • Back button after doing posts on the same page

    - by user441521
    I have 3 pages to my site. The 1st page allows you to select a bunch of options. Those options get sent to the 2nd page to be displayed with some data about those options. From here I can click on a link to get to page 3 on 1 of the options. On page 3 I can create a new/edit/delete all on the same page where reloads come back to page 3. I want a "back" button on page 3 to go back to page 2, but retain the options it had from the original page 1 request. Page 1 has a bunch of check boxes which are passed to page 2 as arrays to the controller. My thought is that I have to pass these arrays (I converted them to lists) to page 3 (even thought page 3 directly doesn't need them) so that page 3 can use them in the back link to it can recreate the values page 1 sent to page 2 originally. I'm using asp.net MVC and when I pass the converted array it seems to convert it to the type instead of actually showing the values: "types=System.Collections.Generic.List" (where types is a List. Is this what is needed or are there other options to getting a "back" button in this case to go back to page 2. It's sort of a pain to pass information to page 3 that isn't really relevant to page 3 except the back button.

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  • Clustering Basics and Challenges

    - by Karoly Vegh
    For upcoming posts it seemed to be a good idea to dedicate some time for cluster basic concepts and theory. This post misses a lot of details that would explode the articlesize, should you have questions, do not hesitate to ask them in the comments.  The goal here is to get some concepts straight. I can't promise to give you an overall complete definitions of cluster, cluster agent, quorum, voting, fencing, split brain condition, so the following is more of an explanation. Here we go. -------- Cluster, HA, failover, switchover, scalability -------- An attempted definition of a Cluster: A cluster is a set (2+) server nodes dedicated to keep application services alive, communicating through the cluster software/framework with eachother, test and probe health status of servernodes/services and with quorum based decisions and with switchover/failover techniques keep the application services running on them available. That is, should a node that runs a service unexpectedly lose functionality/connection, the other ones would take over the and run the services, so that availability is guaranteed. To provide availability while strictly sticking to a consistent clusterconfiguration is the main goal of a cluster.  At this point we have to add that this defines a HA-cluster, a High-Availability cluster, where the clusternodes are planned to run the services in an active-standby, or failover fashion. An example could be a single instance database. Some applications can be run in a distributed or scalable fashion. In the latter case instances of the application run actively on separate clusternodes serving servicerequests simultaneously. An example for this version could be a webserver that forwards connection requests to many backend servers in a round-robin way. Or a database running in active-active RAC setup.  -------- Cluster arhitecture, interconnect, topologies -------- Now, what is a cluster made of? Servers, right. These servers (the clusternodes) need to communicate. This of course happens over the network, usually over dedicated network interfaces interconnecting all the clusternodes. These connection are called interconnects.How many clusternodes are in a cluster? There are different cluster topologies. The most simple one is a clustered pair topology, involving only two clusternodes:  There are several more topologies, clicking the image above will take you to the relevant documentation. Also, to answer the question Solaris Cluster allows you to run up to 16 servers in a cluster. Where shall these clusternodes be placed? A very important question. The right answer is: It depends on what you plan to achieve with the cluster. Do you plan to avoid only a server outage? Then you can place them right next to eachother in the datacenter. Do you need to avoid DataCenter outage? In that case of course you should place them at least in different fire zones. Or in two geographically distant DataCenters to avoid disasters like floods, large-scale fires or power outages. We call this a stretched- or campus cluster, the clusternodes being several kilometers away from eachother. To cover really large distances, you probably need to move to a GeoCluster, which is a different kind of animal.  What is a geocluster? A Geographic Cluster in Solaris Cluster terms is actually a metacluster between two, separate (locally-HA) clusters.  -------- Cluster resource types, agents, resources, resource groups -------- So how does the cluster manage my applications? The cluster needs to start, stop and probe your applications. If you application runs, the cluster needs to check regularly if the application state is healthy, does it respond over the network, does it have all the processes running, etc. This is called probing. If the cluster deems the application is in a faulty state, then it can try to restart it locally or decide to switch (stop on node A, start on node B) the service. Starting, stopping and probing are the three actions that a cluster agent does. There are many different kinds of agents included in Solaris Cluster, but you can build your own too. Examples are an agent that manages (mounts, moves) ZFS filesystems, or the Oracle DB HA agent that cares about the database, or an agent that moves a floating IP address between nodes. There are lots of other agents included for Apache, Tomcat, MySQL, Oracle DB, Oracle Weblogic, Zones, LDoms, NFS, DNS, etc.We also need to clarify the difference between a cluster resource and the cluster resource group.A cluster resource is something that is managed by a cluster agent. Cluster resource types are included in Solaris cluster (see above, e.g. HAStoragePlus, HA-Oracle, LogicalHost). You can group cluster resources into cluster resourcegroups, and switch these groups together from one node to another. To stick to the example above, to move an Oracle DB service from one node to another, you have to switch the group between nodes, and the agents of the cluster resources in the group will do the following:  On node A Shut down the DB Unconfigure the LogicalHost IP the DB Listener listens on unmount the filesystem   Then, on node B: mount the FS configure the IP  startup the DB -------- Voting, Quorum, Split Brain Condition, Fencing, Amnesia -------- How do the clusternodes agree upon their action? How do they decide which node runs what services? Another important question. Running a cluster is a strictly democratic thing.Every node has votes, and you need the majority of votes to have the deciding power. Now, this is usually no problem, clusternodes think very much all alike. Still, every action needs to be governed upon in a productive system, and has to be agreed upon. Agreeing is easy as long as the clusternodes all behave and talk to eachother over the interconnect. But if the interconnect is gone/down, this all gets tricky and confusing. Clusternodes think like this: "My job is to run these services. The other node does not answer my interconnect communication, it must be down. I'd better take control and run the services!". The problem is, as I have already mentioned, clusternodes very much think alike. If the interconnect is gone, they all assume the other node is down, and they all want to mount the data backend, enable the IP and run the database. Double IPs, double mounts, double DB instances - now that is trouble. Also, in a 2-node cluster they both have only 50% of the votes, that is, they themselves alone are not allowed to run a cluster.  This is where you need a quorum device. According to Wikipedia, the "requirement for a quorum is protection against totally unrepresentative action in the name of the body by an unduly small number of persons.". They need additional votes to run the cluster. For this requirement a 2-node cluster needs a quorum device or a quorum server. If the interconnect is gone, (this is what we call a split brain condition) both nodes start to race and try to reserve the quorum device to themselves. They do this, because the quorum device bears an additional vote, that could ensure majority (50% +1). The one that manages to lock the quorum device (e.g. if it's an FC LUN, it SCSI reserves it) wins the right to build/run a cluster, the other one - realizing he was late - panics/reboots to ensure the cluster config stays consistent.  Losing the interconnect isn't only endangering the availability of services, but it also endangers the cluster configuration consistence. Just imagine node A being down and during that the cluster configuration changes. Now node B goes down, and node A comes up. It isn't uptodate about the cluster configuration's changes so it will refuse to start a cluster, since that would lead to cluster amnesia, that is the cluster had some changes, but now runs with an older cluster configuration repository state, that is it's like it forgot about the changes.  Also, to ensure application data consistence, the clusternode that wins the race makes sure that a server that isn't part of or can't currently join the cluster can access the devices. This procedure is called fencing. This usually happens to storage LUNs via SCSI reservation.  Now, another important question: Where do I place the quorum disk?  Imagine having two sites, two separate datacenters, one in the north of the city and the other one in the south part of it. You run a stretched cluster in the clustered pair topology. Where do you place the quorum disk/server? If you put it into the north DC, and that gets hit by a meteor, you lose one clusternode, which isn't a problem, but you also lose your quorum, and the south clusternode can't keep the cluster running lacking the votes. This problem can't be solved with two sites and a campus cluster. You will need a third site to either place the quorum server to, or a third clusternode. Otherwise, lacking majority, if you lose the site that had your quorum, you lose the cluster. Okay, we covered the very basics. We haven't talked about virtualization support, CCR, ClusterFilesystems, DID devices, affinities, storage-replication, management tools, upgrade procedures - should those be interesting for you, let me know in the comments, along with any other questions. Given enough demand I'd be glad to write a followup post too. Now I really want to move on to the second part in the series: ClusterInstallation.  Oh, as for additional source of information, I recommend the documentation: http://docs.oracle.com/cd/E23623_01/index.html, and the OTN Oracle Solaris Cluster site: http://www.oracle.com/technetwork/server-storage/solaris-cluster/index.html

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  • How do you convince the client their application's backend needs a rewrite?

    - by Richard DesLonde
    I have been supporting a LOB winforms application for a client the last 3 years. The application is built with a simple monolithic architecture and uses .NET 2.0. The application is a core part of their operations and its longevity is paramount. It needs to evolve with their evolving business processes, as well as implement improved functionality etc....this brings me to believe that this application needs an overhaul of sorts on the back-end. The problem is changing a back-end is "invisible"...i.e. the user never actually sees it. It's a quality of the system that is changing (stability, maintainability, reliability, longevity), not some functional requirement that will be easily seen...i.e. the ROI is not obvious. There is a lot of new functionality to be added to the front-end as well (user experience). I am considering a strategy of changing the back-end over time...i.e. when making a change or adding a feature to the front-end, change those components in the back-end that are affected, eventually you get to everything. How do I convince the client that we need to rebuild the back-end?

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  • Load HTML frames in a specific order without back button problems?

    - by Joergen Bech
    I have a web page that uses a frameset. Due to scripting and object dependencies, I need to load the frames in a specific order. I have used this example as a template: The JavaScript Source: Navigation: Frames Load Order This loads an empty page in place of the page I need to load last, then replaces it with the correct page after the first page has loaded. However: I also need to use the browser Back button. If you run the sample at the above link, let both frames load, then click the Back button, the top frame reverts to the temporary blank page. It is then necessary to click the Back button again to navigate to the page before the frameset. Is there a way to force frames to load in a specific order without this Back button behavior - or a way to force the Back button to skip the empty page? This needs to work with Internet Explorer 6 and 7 and preferably with Firefox 3 as well.

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  • Is it possible to use Back in Time with Ubuntu One without storing the back up files locally?

    - by leousa
    I use Deja Dup as my back up tool. Love its simplicity and the fact that I can store my back up directly on my Ubuntu One account. Now I really like the flexibility of Back in Time, but I can not find a clean way to store my back up in Ubuntu One. Some threads suggest to use the Ubuntu One folder in your system, and that works, but it also keeps a local copy of the back up in my system, and I do not want that. Any work around for this? Thanks in advance

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  • How do you disable the back button on a lenovo T60?

    - by bobobobo
    There is an awful stupid button on this lenovo T60 i'm using which sends the browser back a page. I really need to disable it. I can't find it anywhere in the Keyboard settings in control panel or the special Lenovo setup utility ("Thinkpad configuration"). Thinkpad Config has everything but keyboard. Its got mouse, trackpoint..

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  • Basics of Join Predicate Pushdown in Oracle

    - by Maria Colgan
    Happy New Year to all of our readers! We hope you all had a great holiday season. We start the new year by continuing our series on Optimizer transformations. This time it is the turn of Predicate Pushdown. I would like to thank Rafi Ahmed for the content of this blog.Normally, a view cannot be joined with an index-based nested loop (i.e., index access) join, since a view, in contrast with a base table, does not have an index defined on it. A view can only be joined with other tables using three methods: hash, nested loop, and sort-merge joins. Introduction The join predicate pushdown (JPPD) transformation allows a view to be joined with index-based nested-loop join method, which may provide a more optimal alternative. In the join predicate pushdown transformation, the view remains a separate query block, but it contains the join predicate, which is pushed down from its containing query block into the view. The view thus becomes correlated and must be evaluated for each row of the outer query block. These pushed-down join predicates, once inside the view, open up new index access paths on the base tables inside the view; this allows the view to be joined with index-based nested-loop join method, thereby enabling the optimizer to select an efficient execution plan. The join predicate pushdown transformation is not always optimal. The join predicate pushed-down view becomes correlated and it must be evaluated for each outer row; if there is a large number of outer rows, the cost of evaluating the view multiple times may make the nested-loop join suboptimal, and therefore joining the view with hash or sort-merge join method may be more efficient. The decision whether to push down join predicates into a view is determined by evaluating the costs of the outer query with and without the join predicate pushdown transformation under Oracle's cost-based query transformation framework. The join predicate pushdown transformation applies to both non-mergeable views and mergeable views and to pre-defined and inline views as well as to views generated internally by the optimizer during various transformations. The following shows the types of views on which join predicate pushdown is currently supported. UNION ALL/UNION view Outer-joined view Anti-joined view Semi-joined view DISTINCT view GROUP-BY view Examples Consider query A, which has an outer-joined view V. The view cannot be merged, as it contains two tables, and the join between these two tables must be performed before the join between the view and the outer table T4. A: SELECT T4.unique1, V.unique3 FROM T_4K T4,            (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3) VWHERE T4.unique3 = V.hundred(+) AND       T4.ten = V.ten(+) AND       T4.thousand = 5; The following shows the non-default plan for query A generated by disabling join predicate pushdown. When query A undergoes join predicate pushdown, it yields query B. Note that query B is expressed in a non-standard SQL and shows an internal representation of the query. B: SELECT T4.unique1, V.unique3 FROM T_4K T4,           (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3             AND T4.unique3 = V.hundred(+)             AND T4.ten = V.ten(+)) V WHERE T4.thousand = 5; The execution plan for query B is shown below. In the execution plan BX, note the keyword 'VIEW PUSHED PREDICATE' indicates that the view has undergone the join predicate pushdown transformation. The join predicates (shown here in red) have been moved into the view V; these join predicates open up index access paths thereby enabling index-based nested-loop join of the view. With join predicate pushdown, the cost of query A has come down from 62 to 32.  As mentioned earlier, the join predicate pushdown transformation is cost-based, and a join predicate pushed-down plan is selected only when it reduces the overall cost. Consider another example of a query C, which contains a view with the UNION ALL set operator.C: SELECT R.unique1, V.unique3 FROM T_5K R,            (SELECT T1.unique3, T2.unique1+T1.unique1             FROM T_5K T1, T_10K T2             WHERE T1.unique1 = T2.unique1             UNION ALL             SELECT T1.unique3, T2.unique2             FROM G_4K T1, T_10K T2             WHERE T1.unique1 = T2.unique1) V WHERE R.unique3 = V.unique3 and R.thousand < 1; The execution plan of query C is shown below. In the above, 'VIEW UNION ALL PUSHED PREDICATE' indicates that the UNION ALL view has undergone the join predicate pushdown transformation. As can be seen, here the join predicate has been replicated and pushed inside every branch of the UNION ALL view. The join predicates (shown here in red) open up index access paths thereby enabling index-based nested loop join of the view. Consider query D as an example of join predicate pushdown into a distinct view. We have the following cardinalities of the tables involved in query D: Sales (1,016,271), Customers (50,000), and Costs (787,766).  D: SELECT C.cust_last_name, C.cust_city FROM customers C,            (SELECT DISTINCT S.cust_id             FROM sales S, costs CT             WHERE S.prod_id = CT.prod_id and CT.unit_price > 70) V WHERE C.cust_state_province = 'CA' and C.cust_id = V.cust_id; The execution plan of query D is shown below. As shown in XD, when query D undergoes join predicate pushdown transformation, the expensive DISTINCT operator is removed and the join is converted into a semi-join; this is possible, since all the SELECT list items of the view participate in an equi-join with the outer tables. Under similar conditions, when a group-by view undergoes join predicate pushdown transformation, the expensive group-by operator can also be removed. With the join predicate pushdown transformation, the elapsed time of query D came down from 63 seconds to 5 seconds. Since distinct and group-by views are mergeable views, the cost-based transformation framework also compares the cost of merging the view with that of join predicate pushdown in selecting the most optimal execution plan. Summary We have tried to illustrate the basic ideas behind join predicate pushdown on different types of views by showing example queries that are quite simple. Oracle can handle far more complex queries and other types of views not shown here in the examples. Again many thanks to Rafi Ahmed for the content of this blog post.

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  • SQL Server – Learning SQL Server Performance: Indexing Basics – Video

    - by pinaldave
    Today I remember one of my older cartoon years ago created for Indexing and Performance. Every single time when Performance is discussed, Indexes are mentioned along with it. In recent times, data and application complexity is continuously growing.  The demand for faster query response, performance, and scalability by organizations is increasing and developers and DBAs need to now write efficient code to achieve this. DBA and Developers A DBA’s role is critical, because a production environment has to run 24×7, hence maintenance, trouble shooting, and quick resolutions are the need of the hour.  The first baby step into any performance tuning exercise in SQL Server involves creating, analysing, and maintaining indexes. Though we have learnt indexing concepts from our college days, indexing implementation inside SQL Server can vary.  Understanding this behaviour and designing our applications appropriately will make sure the application is performed to its highest potential. Video Learning Vinod Kumar and myself we often thought about this and realized that practical understanding of the indexes is very important. One can not master every single aspects of the index. However there are some minimum expertise one should gain if performance is one of the concern. We decided to build a course which just addresses the practical aspects of the performance. In this course, we explored some of these indexing fundamentals and we elaborated on how SQL Server goes about using indexes.  At the end of this course of you will know the basic structure of indexes, practical insights into implementation, and maintenance tips and tricks revolving around indexes.  Finally, we will introduce SQL Server 2012 column store indexes.  We have refrained from discussing internal storage structure of the indexes but have taken a more practical, demo-oriented approach to explain these core concepts. Course Outline Here are salient topics of the course. We have explained every single concept along with a practical demonstration. Additionally shared our personal scripts along with the same. Introduction Fundamentals of Indexing Index Fundamentals Index Fundamentals – Visual Representation Practical Indexing Implementation Techniques Primary Key Over Indexing Duplicate Index Clustered Index Unique Index Included Columns Filtered Index Disabled Index Index Maintenance and Defragmentation Introduction to Columnstore Index Indexing Practical Performance Tips and Tricks Index and Page Types Index and Non Deterministic Columns Index and SET Values Importance of Clustered Index Effect of Compression and Fillfactor Index and Functions Dynamic Management Views (DMV) – Fillfactor Table Scan, Index Scan and Index Seek Index and Order of Columns Final Checklist: Index and Performance Well, we believe we have done our part, now waiting for your comments and feedback. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology, Video

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