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• Huwawei E220 broadband dongle not working

  - by Roshnal

  The problem is, I have used Ubuntu from 6.10 upto 11.10. And upto 11.04 I used my same USB 3G dongle to connect to broadband and it worked fine. But 2 days ago I upgraded to Ubuntu 11.10 and broadband is not working. It detects my dongle and creates a connection without a problem, but when connecting it just keeps on and on for a long time and then say I'm offline. So I did a clean install and the same thing occurred. But I also have a netbook and its got Ubuntu 11.10. I tried using the same dongle for internet on that netbook and it worked fine without any issues. But this isn't a problem with my USB port on my main machine or something like that because I'm also using Windows on my main machine (dual-boot) and its working fine. My hardware: Main computer (one that I'm trying to connect): 2.8GHz dual core Intel 2GB RAM 500GB Sata II HDD 384MB Video Memory (Intel G31/G33 chipset) Ubuntu 11.10 (32bit) My NetBook (broadband working fine): 1.6GHz Intel Atom (dual core) 1GB DDR3 RAM 250GB HDD 128MB Video Memory (Intel something-I-can't-remember) Ubuntu 11.10 (32bit) My dongle is a Huawei E220 and ISP is Dialog GSM (I'm in Sri Lanka) So any idea why this is? I really love Ubuntu and this is bugging me off.. Any help greatly appreciated. Regards, Roshnal

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• Cannot Restore GRUB (Ubuntu 11.04 + Win 7)

  - by Benny

  I'm trying to fix GRUB on my PC, but I'm running into serious issues doing so. Any help would be greatly appreciated as I'm completely crippled right now. Here is the sequence of events for this PC: Installed Windows 7 Split full disk into two partitions (one for win7 and one for multimedia) Long time passed Split one of the partitions into two again Installed Ubuntu 11.04 on new partition A little time passed Windows 7 acting up, reinstall Ubuntu GRUB gone Tried restoring GRUB by mounting and grub-install from live USB Tried switching to a live CD instead of USB (thinking it might be the drive) Now I don't see GRUB and I'm getting "input/output" errors An example i/o error: ubuntu@ubuntu:~$ sudo fdisk -l Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xbe86aff6 Device Boot Start End Blocks Id System /dev/sda1 * 1 48727 391393280 7 HPFS/NTFS /dev/sda2 48727 77063 227612647+ 7 HPFS/NTFS /dev/sda3 77063 91202 113566721 5 Extended /dev/sda5 77063 90622 108908544 83 Linux /dev/sda6 90622 91202 4657152 82 Linux swap / Solaris ubuntu@ubuntu:~$ sudo mount /dev/sda5 /mnt ubuntu@ubuntu:~$ sudo grub-install --root-directory=/mnt /dev/sda mkdir: cannot create directory `/mnt/boot': Input/output error ubuntu@ubuntu:~$ cd /mnt ubuntu@ubuntu:/mnt$ ls ls: cannot access etc: Input/output error

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• How to refactor when all your development is on branches?

  - by Mark

  At my company, all of our development (bug fixes and new features) is done on separate branches. When it's complete, we send it off to QA who tests it on that branch, and when they give us the green light, we merge it into our main branch. This could take anywhere between a day and a year. If we try to squeeze any refactoring in on a branch, we don't know how long it will be "out" for, so it can cause many conflicts when it's merged back in. For example, let's say I want to rename a function because the feature I'm working on is making heavy use of this function, and I found that it's name doesn't really fit its purpose (again, this is just an example). So I go around and find every usage of this function, and rename them all to its new name, and everything works perfectly, so I send it off to QA. Meanwhile, new development is happening, and my renamed function doesn't exist on any of the branches that are being forked off main. When my issue gets merged back in, they're all going to break. Is there any way of dealing with this? It's not like management will ever approve a refactor-only issue so it has to be squeezed in with other work. It can't be developed directly on main because all changes have to go through QA and no one wants to be the jerk that broke main so that he could do a little bit of non-essential refactoring.

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• Control convention for circular movement?

  - by Christian

  I'm currently doing a kind of training project in Unity (still a beginner). It's supposed to be somewhat like Breakout, but instead of just going left and right I want the paddle to circle around the center point. This is all fine and dandy, but the problem I have is: how do you control this with a keyboard or gamepad? For touch and mouse control I could work around the problem by letting the paddle follow the cursor/finger, but with the other control methods I'm a bit stumped. With a keyboard for example, I could either make it so that the Left arrow always moves the paddle clockwise (it starts at the bottom of the circle), or I could link it to the actual direction - meaning that if the paddle is at the bottom, it goes left and up along the circle or, if it's in the upper hemisphere, it moves left and down, both times toward the outer left point of the circle. Both feel kind of weird. With the first one, it can be counter intuitive to press Left to move the paddle right when it's in the upper area, while in the second method you'd need to constantly switch buttons to keep moving. So, long story short: is there any kind of existing standard, convention or accepted example for this type of movement and the corresponding controls? I didn't really know what to google for (control conventions for circular movement was one of the searches I tried, but it didn't give me much), and I also didn't really find anything about this on here. If there is a Question that I simply didn't see, please excuse the duplicate.

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• Is there ever a reason to do all an object's work in a constructor?

  - by Kane

  Let me preface this by saying this is not my code nor my coworkers' code. Years ago when our company was smaller, we had some projects we needed done that we did not have the capacity for, so they were outsourced. Now, I have nothing against outsourcing or contractors in general, but the codebase they produced is a mass of WTFs. That being said, it does (mostly) work, so I suppose it's in the top 10% of outsourced projects I've seen. As our company has grown, we've tried to take more of our development in house. This particular project landed in my lap so I've been going over it, cleaning it up, adding tests, etc etc. There's one pattern I see repeated a lot and it seems so mindblowingly awful that I wondered if maybe there is a reason and I just don't see it. The pattern is an object with no public methods or members, just a public constructor that does all the work of the object. For example, (the code is in Java, if that matters, but I hope this to be a more general question): public class Foo { private int bar; private String baz; public Foo(File f) { execute(f); } private void execute(File f) { // FTP the file to some hardcoded location, // or parse the file and commit to the database, or whatever } } If you're wondering, this type of code is often called in the following manner: for(File f : someListOfFiles) { new Foo(f); } Now, I was taught long ago that instantiated objects in a loop is generally a bad idea, and that constructors should do a minimum of work. Looking at this code it looks like it would be better to drop the constructor and make execute a public static method. I did ask the contractor why it was done this way, and the response I got was "We can change it if you want". Which was not really helpful. Anyway, is there ever a reason to do something like this, in any programming language, or is this just another submission to the Daily WTF?

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• Agile Data Book from O'Reilly Media

  - by Compudicted

  Originally posted on: http://geekswithblogs.net/Compudicted/archive/2013/07/01/153309.aspxAs part of my ongoing self-education and approaching of some free time, yeah, both is a must for every IT person and geek! I have carefully examined the latest trends in the Computersphere with whatever tools I had at my disposal (nothing really fancy was used) and came to a conclusion that for a database pro the *hottest* topic today is undoubtedly the #BigData and all the rapidly growing and spawning ecosystem around it. Having recently immersed myself into the NoSQL world (let me tell here right away NoSQL means Not Only SQL) one book really stood out of the crowd: Book site: http://shop.oreilly.com/product/0636920025054.doDespite being a new book I am sure it will end up on the tables of many Big Data Generalists.In a few dozen words, it is primarily for two reasons:1) The author understands that a  typical business today cannot wait for a Data Scientist for too long to deliver results demanding as usual a very quick turnaround on investments (ROI), and 2) The book covers all the needed and proven modern brick and mortar offerings to get the job done by a relatively newcomer to the Big Data World.It certainly enables such a professional to grow and expand based on the acquired knowledge, and one can truly do it very fast.

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• For a Javascript library, what is the best or standard way to support extensibility

  - by Michael Best

  Specifically, I want to support "plugins" that modify the behavior of parts of the library. I couldn't find much information on the web about this subject. But here are my ideas for how a library could be extensible. The library exports an object with both public and "protected" functions. A plugin can replace any of those functions, thus modifying the library's behavior. Advantages of this method are that it's simple and that the plugin's functions can have full access to the library's "protected" functions. Disadvantages are that the library may be harder to maintain with a larger set of exposed functions and it could be hard to debug if multiple plugins are involved (how to know which plugin modified which function?). The library provides an "add plugin" function that accepts an object with a specific interface. Internally, the library will use the plugin instead of it's own code if appropriate. With this method, the internals of the library can be rearranged more freely as long as it still supports the same plugin interface. This could also support having different plugin interfaces to modify different parts of the library. A disadvantage of this method is that the plugins may have to re-implement code that is already part of the library since the library's internal functions are not exported. The library provides a "set implementation" function that accepts an object inherited from a specific base object. The library's public API calls functions in the implementation object for any functionality that can be modified and the base implementation object includes the core functionality, with both external (to the API) and internal functions. A plugin creates a new implementation object, which inherits from the base object and replaces any functions it wants to modify. This combines advantages and disadvantages of both the other methods.

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• How do I stop CRM from asking for admin credentials when printing report

  - by Ac0ua

  Problem: When printing a report in CRM, I am asked by the UAC for admin credentials. There is a long URL: https://(crm_hostname)/reserved.ReportViewerWebcontrol.axd?ReportSession=(ID)ControlID=(ID)Culture=1333&UICulture=1033&ReportStack=1&OpType=PrintCab Info: There are three users that have the issue laied out here. They are not admins of any kind. It looks like it is asking for permission to allow SQL Server Reporting Services 2008 to run. When I put my credentials in, it just brings up the Print dialog box (this is fine, just stop asking for credentials). I know this might sound silly but I downloaded and installed "SQL Server Reporting Services 2008" hopping my credentials would give permission right from the beginning. Giving the users local admin, I was told is not an option. Note: I did post this on community (dot) dynamics (dot) com but, they are not a very active website. Thanks for any help even if it just points me in the right direction!

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• Easily tell if focused on VirtualBox window?

  - by Benjamin Oakes

  Is there a way to make it very obvious that my VirtualBox window isn't in focus? The problem I'm having is switching between workspaces on Ubuntu or OS X and then trying to type in my Windows virtual machine, only to find that it's not in focus. The Windows window looks like it's in focus (based on the title bar), but I'm actually typing in Firefox on the host machine, for example. It's even worse because the Windows text insertion cursor is blinking to show focus. Ideally, I'd like the VM's display to get unsaturated (e.g. a "partial" grayscale) when not in focus, just to prevent this keyboard-focus problem. Other options would be fine too, as long as I don't have to second guess where my focus is. I'm not using the seamless mode -- the display is all within a window.

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• Glitch-free cross-fades in HTML5

  - by Alexander Gladysh

  In my HTML5 canvas game, I need to cross-fade two sprites which have some glow around them. (Glow is backed into sprites.) Initially, the first sprite is visible. During the cross-fade the first sprite should vanish, and be replaced with the second one. How exactly the cross-fade is done — does not matter, as long as it is smooth and there are no visual glitches. I've tried two techniques: During the cross-fade I simultaneously interpolate alpha of the first sprite from 1.0 to 0.0, and alpha of the second sprite — from 0.0 to 1.0. With this technique I can see background in the middle of the cross-fade. That's because both sprites are semi-transparent most of the time. During the cross-fade I first interpolate alpha of the second sprite from 0.0 to 1.0 (first sprite alpha is at 1.0), and then interpolate alpha of the first sprite from 1.0 to 0.0. With this technique background is not seen, but the glow around sprites flashes during the cross-fide — when both sprites are near the full visibility. In non-HTML5 game I'd use shaders to do cross-fade separately in RGB and alpha channels. Is there a trick to do the cross-fade I need in HTML5 without visual glitches?

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• Benefits of Server-side Coding

  There are numerous advantages to server scripting languages over client side languages in regards to creating web sites that are more compelling compared to a standard static site. Server side scripting are scripts that are executed on a web server during the compilation of data to return to a client. These scripts allow developers to modify the content that is being sent to the user prior to the return of the data to the user as well as store information about the user. In addition, server side scripts allow for a controllable environment in which they can be executed. This cannot be said for client side languages because the developer cannot control the users’ environment compared to a web server. Some users may turn off client scripts, some may be only allow limited access on the system and others may be able to gain full control of the environment.  I have been developing web applications for over 9 years, and I have used server side languages for most of the applications I have built.  Here is a list of common things I have developed with server side scripts. List of Common Generic Functionality Send Email FTP Files Security/ Access Control Encryption URL rewriting Data Access Data Creation I/O Access The one important feature server side languages will help me with on my website is Data Access because my component will be backed with a SQL server database. I believe that form validation is one instance where I might see server-side scripts and JavaScript used interchangeably because it does not matter how or where the data is validated as long as the data that gets inserted is valid. However, I would have to say that my personal experience would have to sway me in deciding what type of languages to use for form validation because they both have advantages and disadvantages based on the each situation.

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• FreeDOS reinstallation -- accidental script change

  - by jerry2144

  I'm extremely new to FreeDOS and I got a new HP desktop computer with the FreeDOS operating system. I messed up and accidentally changed its scripts and messed around with it's boot order. Long story short, I'm getting a disk error when I boot up. I believe I need to just reinstall FreeDOS and all should be good, but I want to get someone's opinion with much more experience than my own. Also, if someone could guide me through the installation process using a DVD installer that would be amazing. I have already downloaded the FreeDOS iso image and unzipped it. I don't know what I need to do now though. Should I even have unzipped it?

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• Computer prints blank pages before and after content

  - by Cpt. Jack

  This would seem like a pretty simple question but I have exhausted every idea I can come up with. I bought a brand new Dell Latitude E5410 not too long ago with Windows 7 OS. I installed office 2010 on the machine right away and have had a printing problem since day one. For some reason every time I print a page, a blank page prints out before and after the content print. This also applies to any other application such as notepad or printing an email. If I have a 6 page document, it still prints out one page before and after every content page. Meaning I get my 6 page document along with 12 blank pages. I can't figure out why this would be some sort of default setting or what would cause this printing configuration. I am the only computer on the network that has this problem and quite frankly I'm getting tired of it. Can anyone help me figure this out or steer me in the right direction to correcting this problem?

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• Mounting Gluster Volumes

  - by Roman Newaza

  I have created Hosted Zone with 2 IP addresses of Gluster Cluster, both IP are returned by dig. After mounting Gluster, I cannot ls mount point as it takes long time. mount shows me it's mounted, but df doesn't. Finally, I have this: ls: cannot access /mnt/storage: Transport endpoint is not connected. But if I mount it with the one of the IP, no problem - volume contents is accessible OS: Ubuntu 11.10 GlusterFS: 3.2.6 Log: http://pastie.org/private/2jgp4h1hnqgzych3djtg I have can telnet storage from client - ports are open.

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• Non-Obvious Topics to Learn for Game Development

  - by ashes999

  I've been writing games for around 10 years now (from QBasic to C# and everything in-between). I need to start stretching my skills into different areas. What are other, surprising topics I should read up on? Expected topics would include the usual suspects: Programming language of your choice Scripting language Source control Project management (or Agile) Graphics API Maybe some AI (A* path-finding?) Physics (projectile physics) Unit testing (automated testing) I'm looking for more esoteric topics; things that you don't expect to need to know, but if you do know them, they make a difference. This could include things like: Art skills (drawing, lighting, colouring, layout, etc.) Natural language processing The physics of sound (sound-waves, doppler effect, etc.) Personally, I feel that having technical art skills (eg. can make decent art-work if you can only come up with ideas; or, following Photoshop/GIMP tutorials) was the most beneficial for me. This is not intended to be an open-ended question; I'm looking for specific skills that helped you and you expect will continue to benefit you in the short- and long-term.

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• Procedural content (settlement) generation

  - by instancedName

  I have, lets say, something like a homework or assignment to do. Roughly said I need to write an algorithm (pseudo code is not necessary, just in depth description) of procedure that would generate settlements, environment and a people to populate it with, as part of some larger world generation procedure. The genre of game is not specified, it could be any genre (rpg, strategy, colony simulation etc.) where interacting with large and extensive world is central to the game. Procedure should be called once per settlement. At the time of calling, world generation procedure makes geography, culture and history input available. Output should be map of the village and it's immediate area, and various potential additional information like myths, history, demographic facts etc. Bonus would be quest ant similar stuff, but that not really my focus at the moment. I will leave quality of the output for later when I actually dig little deeper into this topic. I am free to change parameters as long as I have strong explanation for doing so. Setting of the game is undetermined so I am free to use anything that I like the most. Ok, so my actual question is: Can anyone who has some experience in this field of game design recommend me some good literature, or point me in the direction where I should look/reed/study? I'm somewhat experienced game programmer, but I've never been into game design till now so any help will be great. I want to do this assignment as good as I can. As for deadline, it's not strictly set, but lets say I don't want it to take longer then few weeks, one month at worst case.

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• OpenOffice Calc: How can I count the number of different items with data pilot?

  - by manu

  Hi all, I have a rather long spreadsheet with historical information of issues solved by some user on a colaborative environment. The spreadsheet have the following (relevant) columns date, week no., project, author id, etc... The week no. is calculated from the date, is basically the year concatenated with the week number within that year; for instance, both 2009-02-18 and 2009-02-20 yield the week number 200908 - the 8th week of year 2009; and 2009-02-23 yields 200909 - the 9th week of year 2009. I need to count how many different users (given by author id) contributed to some project, on a weekly basis. I have setup a data pilot with the week as Row Field, the project as the Column Field, and count-author as the Data Field. However, this counts the author id as different instances. This is not what I need. I need to count how many different users contributed to each project on a weekly basis. I expect to get something like: projects week Project1 Project2 Project3 200901 10 2 200902 2 7 Each inner cell containing how many different users contributed. With the count-author configuration, what I get is how many contributions (total) got the project on that week. Is there a way to tell OpenOffice Calc to do what I want?

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• Gain Access to a Facebook account using an email I no longer have access to

  - by Tom Tresansky

  Trying to regain access to a Facebook account I haven't used in years which was set up while I was in school with my school email account, which no longer exists. Don't know the password to the Facebook account. I went here and made a request. Got an email within minutes and and replied to it. That was over week ago. Anyone gone through this before? How long did it take? Any way to expedite the process? Any alternate way to contact Facebook team and get some help with this?

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• Screen flicker -> Severe System Slowdown?

  - by Adam Robinson

  I'm using a Dell D830 laptop, and over the last few weeks it's been developing a very irritating screen flicker problem that leads to the system slowing down almost to the point of unusability. At seemingly random times (no commonality between how long the system has been running, what I was doing, what applications were open, etc.) my screen (I use two external LCD's with the laptop closed in a dock) flickers for a moment, then the system becomes incredibly slow. The screen redraws painfully slowly--almost like what you might expect to see with generic graphics drivers installed--and the entire system is maddeningly unresponsive. The only thing that seems to be able to correct the issue is a restart. I've checked the event logs and nothing out of the ordinary is there, and definitely nothing that's common to all of the events. I'm running XP Pro SP2. Any ideas?

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• Best practice for designing a risk-style board game

  - by jyanks

  I'm just trying to figure out how to set up the code for a game like risk... I would like it to be extensible, so that I can have multiple maps (ie- World, North America, Eurasia, Africa) so hardcoding in the map doesn't seem to make a whole lot of sense I'm a bit confused on how/where items should be stored/accessed. Here are the objects I see the game theoretically using: -Countries/Territories -Cities (Can be contained within territories) -Capitols -Connections -Continents -Map -Troops At the moment, I feel like: -A map should have a list of continents and countries. The continents would be more of a 'logical' thing where the continents would just be lists of countries that are checked for bonuses at the start of turns -Countries should have a list of countries that they're connected to for the connections What I can't figure out is: Where do I store the troops? Do I have an object for every single troop or do I just store the number of troops on a country object as an integer? What about capitols and cities? Do those just have a reference to the country they reside in? Is there anything I'm not seeing here that's going to screw me over in the long run with the way that I'm thinking about things now? Any advice would be appreciated.

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• Migrate Thunderbird 3 Saved Searches Between Accounts

  - by UltraNurd

  Long story short, the sysadmins have moved me to a new mailserver. In the process, they needed to create a separate account in Thunderbird and disable my old account. They took care of all of the mail migration. However, my saved search folders didn't go along for the ride. I have over 20 complex searches that I'd rather not have to reenter manually by hand. You can't drag saved searches between accounts like other folders. I tried closing Thunderbird, doing a find/replace in virtualFolders.dat in my Thunderbird profile folder, saving that file, and reopening Thunderbird, but that didn't appear to do anything. I'm assuming the search folders are also saved in one of the sqlite databases... does anyone know where to look?

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• How to understand computer science as a whole?

  - by MrCellophane

  I am a college student in Computer Science, I have been studying CS for a long time. But even till today, I still feel so confused about a lot of things. First of all, I have solid foundation in alg, data structure, and OOP, but I don't have a clear understanding of the whole system of the subject. I studied database, alg, data structure, OOP, network, software engineering, OS, and a lot of courses. I know what they are, but I don't know how to connect them together. Is there a way to have a clear understanding of the architecture of the subject? And is there a way to know what technology is used to do what? For example, in interviews, when people ask me alg, data str, Java, OS or any other specific field, I could answer, but when they ask some other very general about the field, I have no idea. Well, I know my question maybe a little bit confusing, but what my situation is I don't even know how to ask a clear question. I don't know my question, it's totally a mess in my head. Is there a way to make it clear?

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• Oracle Flashback Technology - Webcast 9th June 2010

  - by Alex Blyth

  Hi All Here are the details for webcast on Oracle Flashback Technologies on Wednesday (9th June 2010) beginning at 1.30pm (Sydney, Australia Time). The Oracle Database architecture leverages the unique technological advances in the area of database recovery due to human errors. Oracle Flashback Technology provides a set of new features to view and rewind data back and forth in time. The Flashback features offer the capability to query historical data, perform change analysis, and perform self-service repair to recover from logical corruptions while the database is online. With Oracle Flashback Technology, you can indeed undo the past! Oracle9i introduced Flashback Query to provide a simple, powerful and completely non-disruptive mechanism for recovering from human errors. It allows users to view the state of data at a point in time in the past without requiring any structural changes to the database. Oracle Database 10g extended the Flashback Technology to provide fast and easy recovery at the database, table, row, and transaction level. Flashback Technology revolutionizes recovery by operating just on the changed data. The time it takes to recover the error is now equal to the same amount of time it took to make the mistake. Oracle 10g Flashback Technologies includes Flashback Database, Flashback Table, Flashback Drop, Flashback Versions Query, and Flashback Transaction Query. Flashback technology can just as easily be utilized for non-repair purposes, such as historical auditing with Flashback Query and undoing test changes with Flashback Database. Oracle Database 11g introduces an innovative method to manage and query long-term historical data with Flashback Data Archive. This release also provides an easy, one-step transaction backout operation, with the new Flashback Transaction capability. Webcast is at http://strtc.oracle.com (IE6, 7 & 8 supported only)Conference ID for the webcast is 6690835Conference Key: flashbackEnrollment is required. Please click here to enroll.Please use your real name in the name field (just makes it easier for us to help you out if we can't answer your questions on the call) Audio details: NZ Toll Free - 0800 888 157 orAU Toll Free - 1800420354 (or +61 2 8064 0613)Meeting ID: 7914841Meeting Passcode: 09062010 Talk to you all Wednesday 9th June Alex

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• Why is my NTP controlled computer clock two minutes ahead?

  - by Martin Liversage

  The clock in my computer is configured to be synchronized using NTP. To verify this I have tried two NTP clients using various NTP servers. My computer and the NTP clients are in complete agreement about the current time even across a wide range of NTP servers. I also have a GPS and my national phone company provides an accurate clock available by calling a specific phone number. Both my GPS and the phone company agrees on the current time. However, my computer is almost precisely two minutes (or 1 minute and 59 seconds) ahead of what I believe to be the "real" current time where I live. Why is my computer two minutes ahead? I realize that synchronizing clocks using the internet may not be entirely accurate as there is latency, but two minutes is a very long time on the internet. Is NTP really two minutes ahead? I'm running Windows 7 and live in the time zone UTC+1, but I don't think that is important in understanding my problem.

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• How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?

  - by Stu Thompson

  Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved our servers from a premium hosting centric vendor to a barebones rack pusher in a tier IV data center. (Literally across the street.) This ment doing much more ourselves--things like networking, storage and monitoring. As part the big move, to replace our leased direct attached storage from the hosting company, I built a 9TB two-node NAS based on SuperMicro chassises, 3ware RAID cards, Ubuntu 10.04, two dozen SATA disks, DRBD and . It's all lovingly documented in three blog posts: Building up & testing a new 9TB SATA RAID10 NFSv4 NAS: Part I, Part II and Part III. We also setup a Cacit monitoring system. Recently we've been adding more and more data points, like SMART values. I could not have done all this without the awesome boffins at ServerFault. It's been a fun and educational experience. My boss is happy (we saved bucket loads of $$$), our customers are happy (storage costs are down), I'm happy (fun, fun, fun). Until yesterday. Outage & Recovery: Some time after lunch we started getting reports of sluggish performance from our application, an on-demand streaming media CMS. About the same time our Cacti monitoring system sent a blizzard of emails. One of the more telling alerts was a graph of iostat await. Performance became so degraded that Pingdom began sending "server down" notifications. The overall load was moderate, there was not traffic spike. After logging onto the application servers, NFS clients of the NAS, I confirmed that just about everything was experiencing highly intermittent and insanely long IO wait times. And once I hopped onto the primary NAS node itself, the same delays were evident when trying to navigate the problem array's file system. Time to fail over, that went well. Within 20 minuts everything was confirmed to be back up and running perfectly. Post-Mortem: After any and all system failures I perform a post-mortem to determine the cause of the failure. First thing I did was ssh back into the box and start reviewing logs. It was offline, completely. Time for a trip to the data center. Hardware reset, backup an and running. In /var/syslog I found this scary looking entry: Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_00], 6 Currently unreadable (pending) sectors Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_07], SMART Prefailure Attribute: 1 Raw_Read_Error_Rate changed from 171 to 170 Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 16 Currently unreadable (pending) sectors Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 4 Offline uncorrectable sectors Nov 15 06:49:45 umbilo smartd[2827]: Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error Nov 15 06:49:45 umbilo smartd[2827]: # 1 Short offline Completed: read failure 90% 6576 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 2 Short offline Completed: read failure 90% 6087 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 3 Short offline Completed: read failure 10% 5901 656821791 Nov 15 06:49:45 umbilo smartd[2827]: # 4 Short offline Completed: read failure 90% 5818 651637856 Nov 15 06:49:45 umbilo smartd[2827]: So I went to check the Cacti graphs for the disks in the array. Here we see that, yes, disk 7 is slipping away just like syslog says it is. But we also see that disk 8's SMART Read Erros are fluctuating. There are no messages about disk 8 in syslog. More interesting is that the fluctuating values for disk 8 directly correlate to the high IO wait times! My interpretation is that: Disk 8 is experiencing an odd hardware fault that results in intermittent long operation times. Somehow this fault condition on the disk is locking up the entire array Maybe there is a more accurate or correct description, but the net result has been that the one disk is impacting the performance of the whole array. The Question(s) How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt? Am I being naïve to think that the RAID card should have dealt with this? How can I prevent a single misbehaving disk from impacting the entire array? Am I missing something?

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