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  • Explaining Explain Plan Notes for Auto DOP

    - by jean-pierre.dijcks
    I've recently gotten some questions around "why do I not see a parallel plan" while Auto DOP is on (I think)...? It is probably worthwhile to quickly go over some of the ways to find out what Auto DOP was thinking. In general, there is no need to go tracing sessions and look under the hood. The thing to start with is to do an explain plan on your statement and to look at the parameter settings on the system. Parameter Settings to Look At First and foremost, make sure that parallel_degree_policy = AUTO. If you have that parameter set to LIMITED you will not have queuing and we will only do the auto magic if your objects are set to default parallel (so no degree specified). Next you want to look at the value of parallel_degree_limit. It is typically set to CPU, which in default settings equates to the Default DOP of the system. If you are testing Auto DOP itself and the impact it has on performance you may want to leave it at this CPU setting. If you are running concurrent statements you may want to give this some more thoughts. See here for more information. In general, do stick with either CPU or with a specific number. For now avoid the IO setting as I've seen some mixed results with that... In 11.2.0.2 you should also check that IO Calibrate has been run. Best to simply do a: SQL> select * from V$IO_CALIBRATION_STATUS; STATUS        CALIBRATION_TIME ------------- ---------------------------------------------------------------- READY         04-JAN-11 10.04.13.104 AM You should see that your IO Calibrate is READY and therefore Auto DOP is ready. In any case, if you did not run the IO Calibrate step you will get the following note in the explain plan: Note -----    - automatic DOP: skipped because of IO calibrate statistics are missing One more note on calibrate_io, if you do not have asynchronous IO enabled you will see:  ERROR at line 1: ORA-56708: Could not find any datafiles with asynchronous i/o capability ORA-06512: at "SYS.DBMS_RMIN", line 463 ORA-06512: at "SYS.DBMS_RESOURCE_MANAGER", line 1296 ORA-06512: at line 7 While this is changed in some fixes to the calibrate procedure, you should really consider switching asynchronous IO on for your data warehouse. Explain Plan Explanation To see the notes that are shown and explained here (and the above little snippet ) you can use a simple explain plan mechanism. There should  be no need to add +parallel etc. explain plan for <statement> SELECT PLAN_TABLE_OUTPUT FROM TABLE(DBMS_XPLAN.DISPLAY()); Auto DOP The note structure displaying why Auto DOP did not work (with the exception noted above on IO Calibrate) is like this: Automatic degree of parallelism is disabled: <reason> These are the reason codes: Parameter -  parallel_degree_policy = manual which will not allow Auto DOP to kick in  Hint - One of the following hints are used NOPARALLEL, PARALLEL(1), PARALLEL(MANUAL) Outline - A SQL outline of an older version (before 11.2) is used SQL property restriction - The statement type does not allow for parallel processing Rule-based mode - Instead of the Cost Based Optimizer the system is using the RBO Recursive SQL statement - The statement type does not allow for parallel processing pq disabled/pdml disabled/pddl disabled - For some reason (alter session?) parallelism is disabled Limited mode but no parallel objects referenced - your parallel_degree_policy = LIMITED and no objects in the statement are decorated with the default PARALLEL degree. In most cases all objects have a specific degree in which case Auto DOP will honor that degree. Parallel Degree Limited When Auto DOP does it works you may see the cap you imposed with parallel_degree_limit showing up in the note section of the explain plan: Note -----    - automatic DOP: Computed Degree of Parallelism is 16 because of degree limit This is an obvious indication that your are being capped for this statement. There is one quite interesting one that happens when you are being capped at DOP = 1. First of you get a serial plan and the note changes slightly in that it does not indicate it is being capped (we hope to update the note at some point in time to be more specific). It right now looks like this: Note -----    - automatic DOP: Computed Degree of Parallelism is 1 Dynamic Sampling With 11.2.0.2 you will start seeing another interesting change in parallel plans, and since we are talking about the note section here, I figured we throw this in for good measure. If we deem the parallel (!) statement complex enough, we will enact dynamic sampling on your query. This happens as long as you did not change the default for dynamic sampling on the system. The note looks like this: Note ----- - dynamic sampling used for this statement (level=5)

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  • How Does AutoPatch Handle Shared E-Business Suite Products?

    - by Steven Chan
    Space... is big. Really big. You just won't believe how vastly hugely mindbogglingly big it is.~ Douglas AdamsDouglas Adams could have been talking about the E-Business Suite.  Depending upon whom you ask (and how you count them), there are between 200 to 240 products in Oracle E-Business Suite.  The products that make up Oracle E-Business Suite are tightly integrated. Some of these products are known as shared or dependent products. Installed and registered automatically by Rapid Install, such products depend on components from other products for full functionality.For example:General Ledger (GL) depends on Application Object Library (FND) and Oracle Receivables (AR)Inventory (INV) depends on FND and GLReceivables (AR) depends on FND, INV, and GLIt can sometimes be challenging to craft a patching strategy for these types of product dependencies.  To help you with that, our Applications Database (AD) team has recently published a new document that describes the actions AutoPatch takes with shared Oracle E-Business Suite products:Patching Shared Oracle E-Business Suite Products (Note 1069099.1)

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  • When and why you should use void (instead of i.e. bool/int)

    - by Jonas
    I occasionally run into methods where a developer chose to return something which isn't critical to the function. I mean, when looking at the code, it apparently works just as nice as a void and after a moment of thought, I ask "Why?" Does this sound familiar? Sometimes I would agree that most often it is better to return something like a bool or int, rather then just do a void. I'm not sure though, in the big picture, about the pros and cons. Depending on situation, returning an int can make the caller aware of the amount of rows or objects affected by the method (e.g., 5 records saved to MSSQL). If a method like "InsertSomething" returns a boolean, I can have the method designed to return true if success, else false. The caller can choose to act or not on that information. On the other hand, May it lead to a less clear purpose of a method call? Bad coding often forces me to double-check the method content. If it returns something, it tells you that the method is of a type you have to do something with the returned result. Another issue would be, if the method implementation is unknown to you, what did the developer decide to return that isn't function critical? Of course you can comment it. The return value has to be processed, when the processing could be ended at the closing bracket of method. What happens under the hood? Did the called method get false because of a thrown error? Or did it return false due to the evaluated result? What are your experiences with this? How would you act on this?

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  • Get entities ids from two similar collections using one method

    - by Patryk Roszczyniala
    I've got two lists: List<Integer, ZooEntity> zoos; List<Integer, List<ZooEntity>> groupOfZoos; These operations will return collections of values: Collection<ZooEntity> cz = zoos.values(); Collection<List<ZooEntity>> czList = groupOfZoos.values(); What I want to achieve is to get list of all zoo ids. List<Integer> zooIds = cz ids + czList ids; Of course I can create two methods to do what I want: public List<Integer> getIdsFromFlatList(Collection<ZooEntity> list) { List<Integer> ids = new ArrayList<Integer>(); for (ZooEntity z : list) { ids.add(z.getId()); } return ids; } public List<Integer> getIdsFromNestedList(Collection<List<ZooEntity>> list) { List<Integer> ids = new ArrayList<Integer>(); for (List<ZooEntity> zList : list) { for (ZooEntity z : zList) { ids.add(z.getId()); } } return ids; } As you can see those two methods are very similar and here is my question: Is it good to create one method (for example using generics) which will get ids from those two lists (zoos and groupOfZoos). If yes how it should look like? If no what is the best solution? BTW. This is only the example. I've got very similar problem at job and I want to do it in preety way (I can't change enities, I can change only getIds...() methods).

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  • Recap - SQL Saturday 151 in Orlando

    - by KKline
    It's always a feel-good experience for me to return to SQL Saturday in Orlando, the place where SQL Saturdays were started by Andy Warren ( Twitter | Blog ). On this trip, I delivered a full-day, pre-conference seminar on Troubleshooting and Performance Tuning SQL Server. I also delivered a session on SQL Server Internals and Architecture to a totally packed house. For those of you who emailed me directly, here's the link for the special SQL Sentry offer . I got to attend the extended events session...(read more)

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  • Should main method be only consists of object creations and method calls?

    - by crucified soul
    A friend of mine told me that, the best practice is class containing main method should be named Main and only contains main method. Also main method should only parse inputs, create other objects and call other methods. The Main class and main method shouldn't do anything else. Basically what he is saying that class containing main method should be like: public class Main { public static void main(String[] args) { //parse inputs //create other objects //call methods } } Is it the best practice?

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  • What non-programming tools do programmers use?

    - by user828584
    I'm reading code complete with the intention of learning how to better structure my code, but I'm also learning a lot about how many aspects of programming something there are that aren't just writing the code. The book talks a lot about problem definition, determining the requirements, defining the structure, designing the code, etc. What tools are used for these non-writing steps of programming? Is there software that will help me design and plan out what I'm going to write before I do?

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  • how to programtically build a grid of interlocking but random sized squares

    - by Mrwolfy
    I want to create a two dimensional layout of rectangular shapes, a grid made up of random sized cubes. The cubed should fit together and have equal padding or margin (space between). Kind of like a comic book layout, or more like the image attached. How could I do this procedurally? Practically, I would probably be using Python and some graphic software to render an image, but I don't know the type of algorithm (or whatnot) I would need to use to generate the randomized grid.

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  • What is the best approach for inline code comments?

    - by d1egoaz
    We are doing some refactoring to a 20 years old legacy codebase, and I'm having a discussion with my colleague about the comments format in the code (plsql, java). There is no a default format for comments, but in most cases people do something like this in the comment: // date (year, year-month, yyyy-mm-dd, dd/mm/yyyy), (author id, author name, author nickname) and comment the proposed format for future and past comments that I want is: // {yyyy-mm-dd}, unique_author_company_id, comment My colleague says that we only need the comment, and must reformat all past and future comments to this format: // comment My arguments: I say for maintenance reasons, it's important to know when and who did a change (even this information is in the SCM). The code is living, and for that reason has a history. Because without the change dates it's impossible to know when a change was introduced without open the SCM tool and search in the long object history. because the author is very important, a change of authors is more credible than a change of authory Agility reasons, no need to open and navigate through the SCM tool people would be more afraid to change something that someone did 15 years ago, than something that was recently created or changed. etc. My colleague's arguments: The history is in the SCM Developers must not be aware of the history of the code directly in the code Packages gets 15k lines long and unstructured comments make these packages harder to understand What do you think is the best approach? Or do you have a better approach to solve this problem?

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  • Programmers and tech email: Do you actually read all of them?

    - by AdityaGameProgrammer
    Email Alerts, Blog /Forum updates, discussion subscriptions general programming/technology update emails that we often subscribe to.Do you actually read them ? or go direct to the source when you find time. often we might the mail of programmers filled with loads of unread subscription mail from technology they previously were following or worked on or things they wish to follow .some or a majority of these mail just keep on piling up . i personally have few updates that i wish i read but constantly avoid and keep of for latter and finally delete them in effort keep the in box clean. few questions come to mind regarding this Do you keep such mail in separate accounts? Do you read all the mail you have subscribed to? Do you ever unsubscribe to any such email if you aren't reading them? How much do you really value these email. Lastly do you keep your in box clean ? wish to deal with this in a better way.

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  • Should a programmer take writing lessons to enhance code expressiveness?

    - by Jose Faeti
    Given that programmers are authors and write code to express abstract thoughts and concepts, and good code should be read by other programmers without difficulties and misunderstandings, should a programmer take writing lessons to write better code? Abstracting concepts and real world problems/entities is an important part of writing good code, and a good mastery of the language used for coding should allow the programmer to express his thoughts more easily, or in a better way. Besides, when trying to write or rewrite some code to make it better, much time can be spent in deciding the names for functions, variables or data structures. I think this could also help to avoid writing code with more than one meaning, often cause of misunderstanding between different programmers. Code should always express clearly its function unambiguously.

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  • How do you approach tutorials

    - by aurel
    Hi I get lots of interesting tutorials through feeds and sometimes I implement them step by step, other times I just read through them and note anything that I do not know. when ever I implement them I takes a long time - starting the project, typing the code (as I feel there is no point to copy and paste ), then going back and forth between browser and editing program All in all, I am interested to know how do you learn from the tutorials (I'm no where close to being an expert). Or if you don't use tutorials, is there any other way to learn? Thanks a lot

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  • Should my colleagues review each others code from source control system?

    - by Daniel Excinsky
    Hi everybody. So that's my story: one of my colleagues uses to review all the code, hosted to revision system. I'm not speaking about adequate review of changes in parts that he belongs to. He watches the code file to file, line to line. Every new file and every modified. I feel just like being spied on! My guess is that if code was already hosted to control system, you should trust it as workable at least. My question is, maybe I'm just too paranoiac and practice of reviewing each others code is good? P.S: We're team of only three developers, and I fear that if there will be more of us, colleague just won't have time to review all the the code we'll write.

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  • How to structure a project that supports multiple versions of a service?

    - by Nick Canzoneri
    I'm hoping for some tips on creating a project (ASP.NET MVC, but I guess it doesn't really matter) against multiples versions of a service (in this case, actually multiple sets of WCF services). Right now, the web app uses only some of the services, but the eventual goal would be to use the features of all of the services. The code used to implement a service feature would likely be very similar between versions in most cases (but, of course, everything varies). So, how would you structure a project like this? Separate source control branches for each different version? Kind of shying away from this because I don't feel like branch merging should be something that we're going to be doing really often. Different project/solution files in the same branch? Could link the same shared projects easily Build some type of abstraction layer on top of the services, so that no matter what service is being used, it is the same to the web application?

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  • What information must never appear in logs?

    - by MainMa
    I'm about to write the company guidelines about what must never appear in logs (trace of an application). In fact, some developers try to include as many information as possible in trace, making it risky to store those logs, and extremely dangerous to submit them, especially when the customer doesn't know this information is stored, because she never cared about this and never read documentation and/or warning messages. For example, when dealing with files, some developers are tempted to trace the names of the files. For example before appending file name to a directory, if we trace everything on error, it will be easy to notice for example that the appended name is too long, and that the bug in the code was to forget to check for the length of the concatenated string. It is helpful, but this is sensitive data, and must never appear in logs. In the same way: Passwords, IP addresses and network information (MAC address, host name, etc.)¹, Database accesses, Direct input from user and stored business data must never appear in trace. So what other types of information must be banished from the logs? Are there any guidelines already written which I can use? ¹ Obviously, I'm not talking about things as IIS or Apache logs. What I'm talking about is the sort of information which is collected with the only intent to debug the application itself, not to trace the activity of untrusted entities. Edit: Thank you for your answers and your comments. Since my question is not too precise, I'll try to answer the questions asked in the comments: What I'm doing with the logs? The logs of the application may be stored in memory, which means either in plain on hard disk on localhost, in a database, again in plain, or in Windows Events. In every case, the concern is that those sources may not be safe enough. For example, when a customer runs an application and this application stores logs in plain text file in temp directory, anybody who has a physical access to the PC can read those logs. The logs of the application may also be sent through internet. For example, if a customer has an issue with an application, we can ask her to run this application in full-trace mode and to send us the log file. Also, some application may sent automatically the crash report to us (and even if there are warnings about sensitive data, in most cases customers don't read them). Am I talking about specific fields? No. I'm working on general business applications only, so the only sensitive data is business data. There is nothing related to health or other fields covered by specific regulations. But thank you to talk about that, I probably should take a look about those fields for some clues about what I can include in guidelines. Isn't it easier to encrypt the data? No. It would make every application much more difficult, especially if we want to use C# diagnostics and TraceSource. It would also require to manage authorizations, which is not the easiest think to do. Finally, if we are talking about the logs submitted to us from a customer, we must be able to read the logs, but without having access to sensitive data. So technically, it's easier to never include sensitive information in logs at all and to never care about how and where those logs are stored.

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  • Best approach for utility class library using Visual Studio

    - by gregsdennis
    I have a collection of classes that I commonly (but not always) use when developing WPF applications. The trouble I have is that if I want to use only a subset of the classes, I have three options: Distribute the entire DLL. While this approach makes code maintenance easier, it does require distributing a large DLL for minimal code functionality. Copy the classes I need to the current application. This approach solves the problem of not distributing unused code, but completely eliminates code maintenance. Maintain each class/feature in a separate project. This solves both problems from above, but then I have dramatically increased the number of files that need to be distributed, and it bloats my VS solution with tiny projects. Ideally, I'd like a combination of 1 & 3: A single project that contains all of my utility classes but builds to a DLL containing only the classes that are used in the current application. Are there any other common approaches that I haven't considered? Is there any way to do what I want? Thank you.

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  • How should programmers handle email-username identity theft?

    - by Craige
    Background I recently signed up for an iTunes account, and found that somebody had fraudulently used MY email to register their iTunes account. Why Apple did not validate the email address, I will never know. Now I am told that I cannot use my email address to register a new iTunes account, as this email address is linked to an existing account. This got be thinking... Question How should we as developers handle email/identity theft? Obviously, we should verify that an email address belongs to the person it is said to belong to. Why Apple did not do this in my case, I have no idea. But lets pretend we use email address for login/account identification, and something slipped though the cracks (be it our end, or the users). How should we handle reports of fraudulent accounts?

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  • How to learn programming for a medium scale project form a beginner? [closed]

    - by Lin Xiangyu
    I study programming by myself.I have learn servel programming languages. but I never write a project more than 1000 lines. I know the best way to improve programming skills is practise. The problem is many books, just talk about the programming language, or talk about build a project from a high level. Fews of books will teach how to build a middle scale project. For example, I want to build a simple HTTP Server(Nor like Apache or just a simple listenr to a port), a Markdown Parser, or a download tools just like emule or wget. I don't know what to do. I may found peaces of code in the web, or found familiar project in the Github. I don't know how to read the code. I want to some tutorial that can told me how to build the project step by step, teacher me how to write thousands lines of code. Any suggest?

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  • Are there any memorization techniques that exist for programmers? [closed]

    - by Akromyk
    I just watched this video on Ted.com entitled: Joshua Foer: Feats of memory anyone can do and it got me thinking about memory from a programmers perspective. There are so many abstract concepts and syntactic nuances we encounter daily, and yet we still manage to remember enough information to be productive. The memory palace may help in remembering someone's name or a random story but are there any memorization techniques that can better aid programmers?

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  • Are programmers getting lazier and less competent

    - by Skeith
    I started programming in C++ at uni and loved it. In the next term we changed to VB6 and I hated it. I could not tell what was going on, you drag a button to a form and the ide writes the code for you. While I hated the way VB functioned I cannot argue that it was faster and easier than doing the same thing in C++ so i can see why it is a popular language. Now I am not calling VB developers lazy in just saying it easier than C++ and I have noticed that a lot of newer languages are following this trend such a C#. This leads me to think that as more business want quick results more people will program like this and sooner or later there will be no such thing as what we call programming now. Future programmers will tell the computer what they want and the compiler will write the program for them like in star trek. Is this just an under informed opinion of a junior programmer or are programmers getting lazier and less competent in general? EDIT: A lot of answers say why re invent the wheel and I agree with this but when there are wheels available people are not bothering to learn how to make the wheel. I can google how to do pretty much anything in any language and half the languages do so much for you when it come to debugging they have no idea what there code does of how to fix the error. That's how I cam up with the theory that programmers are becoming lazier and less competent as no one cares how stuff works just that it does until it does not.

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  • Absolute statements in IT that are wrong

    - by Dan McGrath
    I was recently in a discussion about the absolute statement "It costs more in programming time to optimise software than it costs to throw hardware at a problem". The general thought (of which I agree with) is that as an absolute statement this is wrong. There are too many variables to ever generalise in such a way. What other statements do you hear about software/programming that simply do not work as an absolute and why?

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  • Simple vs Complex (but performance efficient) solution - which one to choose and when?

    - by ManojGumber
    I have been programming for a couple of years and have often found myself at a dilemma. There are two solutions - one is simple one i.e. simple approach, easier to understand and maintain. It involves some redundancy, some extra work (extra IO, extra processing) and therefore is not the most optimal solution. but other uses a complex approach,difficult to implement, often involving interaction between lot of modules and is a performance efficient solution. Which solution should I strive for when I do not have hard performance SLA to meet and even the simple solution can meet the performance SLA? I have felt disdain among my fellow developers for simple solution. Is it good practice to come up with most optimal complex solution if your performance SLA can be met by a simple solution?

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  • Looking for tips on managing complexity with SCM repositories

    - by Philip Regan
    I am a solo developer in my department and I have a lot of individual projects, all created and managed by me. I started using SVN at ProjectLocker via Versions on the Mac a couple years ago when the variety of projects started getting unwieldy. Scenario 1: Now I have a process that is of reasonable complexity it can be broken up into multiple smaller applications and they all share files. In one phase, there is a single shared file—a constants file—that is shared between a Cocoa app and an iPhone app framework. In the second phase, the iPhone app framework will be used to create individual apps of the same ilk—controller classes and what not will all be the same—but with different content in each. The problem that I am running across is that the file in the first phase is in one repository with the application that started it, and the app framework is in a second, separate repository. Scenario 2: I have another application framework that partially relies on code from an open source project. This is all internal, non-commerical work, but again, the application framework is going to be used to create a variety of unique products and processes. So, now I have an internally managed repository and an externally managed one out of my control. I make little changes to the open source code to meet the needs of my framework when there is an update I download, but I never commit back into the external repository (though, now that I think about it, I don't think I'm committing it to mine either. Oops). The Problem I have all of this set up on my production Mac quite nicely, but duplicating and subsequently maintaining that environment on my laptop has been challenging. For Scenario 1, I've thought of merging these two projects together into the same repository because they are, for all intents and purposes inextricably linked. But, Scenario 2, I think I'm stuck just managing files as best I can. The Question I'm wondering if anyone has any tips on how to manage either of these situations, as well as other complex SCM scenarios when it comes to linking various files from various repositories together. My familiarity with SVN only comes from my work with Versions. It's been great, but I'm a little out of my depth here.

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  • Techniques to read code written by others?

    - by Simon
    Are there any techniques that you find useful or follow when it comes to reading and understanding code written by others when Direct Knowledge Transfer/meeting the person who wrote the code is not an option. One of the techniques that I follow when dealing with legacy code is by adding additional debugging statements and based on the values I figure out the flow/logic. This can be tedious at times. Hence the reason behind this question, Are there any other techniques being widely practiced or that you personally follow when it comes to dealing with code written by other people/colleagues/open-source team?

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