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• How to delete/edit files from readonly filesystem

  - by Santosh Linkha

  I am having problem with my memory device (actually a memory card that act external memory device like pendrive). experimentx@workmateX:/var/www/zendtest$ sudo rm /media/A88F-8788/python-2.7.1-docs-html.zip rm: cannot remove `/media/A88F-8788/python-2.7.1-docs-html.zip': Read-only file system I tried to change the file permission of the system but that doesn't work experimentx@workmateX:/var/www/zendtest$ sudo chmod 0777 /media/A88F-8788/python-2.7.1-docs-html.zip chmod: changing permissions of `/media/A88F-8788/python-2.7.1-docs-html.zip': Read-only file system But it perfectly works on windows. UPDATE On opening the drive and running command sudo mount -o remount,rw /media/A88F-8788 /var/log/syslog: Mar 23 15:29:48 workmateX kernel: [18042.257407] fat_get_cluster: 11 callbacks suppressed Mar 23 15:29:48 workmateX kernel: [18042.257414] FAT: Filesystem error (dev sdb1) Mar 23 15:29:48 workmateX kernel: [18042.257418] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:29:48 workmateX kernel: [18042.257425] FAT: Filesystem has been set read-only Mar 23 15:29:48 workmateX kernel: [18042.258187] FAT: Filesystem error (dev sdb1) Mar 23 15:29:48 workmateX kernel: [18042.258194] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.333787] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.333795] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.335949] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.335957] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.354903] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.354911] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.357213] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.357221] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.359547] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.359555] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.361929] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.361936] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.377416] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.377424] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.379384] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.379392] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.381898] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.381906] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:35 workmateX kernel: [18149.383764] FAT: Filesystem error (dev sdb1) Mar 23 15:31:35 workmateX kernel: [18149.383772] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.569747] fat_get_cluster: 11 callbacks suppressed Mar 23 15:31:40 workmateX kernel: [18154.569754] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.569758] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.569765] FAT: Filesystem has been set read-only Mar 23 15:31:40 workmateX kernel: [18154.572022] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.572029] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.582933] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.582941] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.585921] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.585929] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.587819] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.587827] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.597547] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.597555] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.599503] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.599511] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.602896] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.602905] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.615338] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.615346] fat_get_cluster: invalid cluster chain (i_pos 0) Mar 23 15:31:40 workmateX kernel: [18154.618574] FAT: Filesystem error (dev sdb1) Mar 23 15:31:40 workmateX kernel: [18154.618581] fat_get_cluster: invalid cluster chain (i_pos 0) var/log/message: Mar 23 15:29:48 workmateX kernel: [18042.257407] fat_get_cluster: 11 callbacks suppressed Mar 23 15:31:40 workmateX kernel: [18154.569747] fat_get_cluster: 11 callbacks suppressed

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• SQL SERVER – Retrieve and Explore Database Backup without Restoring Database – Idera virtual databas

  - by pinaldave

  I recently downloaded Idera’s SQL virtual database, and tested it. There are a few things about this tool which caught my attention. My Scenario It is quite common in real life that sometimes observing or retrieving older data is necessary; however, it had changed as time passed by. The full database backup was 40 GB in size, and, to restore it on our production server, it usually takes around 16 to 22 minutes, depending on the load server that is usually present. This range in time varies from one server to another as per the configuration of the computer. Some other issues we used to have are the following: When we try to restore a large 40-GB database, we needed at least that much space on our production server. Once in a while, we even had to make changes in the restored database, and use the said changed and restored database for our purpose, making it more time-consuming. My Solution I have heard a lot about the Idera’s SQL virtual database tool.. Well, right after we started to test this tool, we found out that it really delivers what it promises. Using this software was very easy and we were able to restore our database from backup in less than 2 minutes, sparing us from the usual longer time of 16–22 minutes. The needful was finished in a total of 10 minutes. Another interesting observation is that there is no need to have an additional space for restoring the database. For complete database restoration, the single additional MB on the drive is not required anymore. We can use the database in the same way as our regular database, and there is no need for any additional configuration and setup. Let us look at the most relevant points of this product based on my initial experience: Quick restoration of the database backup No additional space required for database restoration virtual database has no physical .MDF or .LDF The database which is restored is, in fact, the backup file converted in the virtual database. DDL and DML queries can be executed against this virtually restored database. Regular backup operation can be implemented against virtual database, creating a physical .bak file that can be used for future use. There was no observed degradation in performance on the original database as well the restored virtual database. Additional T-SQL queries can be let off on the virtual database. Well, this summarizes my quick review. And, as I was saying, I am very impressed with the product and I plan to explore it more. There are many features that I have noticed in this tool, which I think can be very useful if properly understood. I had taken a few screenshots using my demo database afterwards. Let us see what other things this tool can do besides the mentioned activities. I am surprised with its performance so I want to know how exactly this feature works, specifically in the matter of why it does not create any additional files and yet, it still allows update on the virtually restored database. I guess I will have to send an e-mail to the developers of Idera and try to figure this out from them. I think this tool is very useful, and it delivers a high level of performance way more than what I expected. Soon, I will write a review for additional uses of SQL virtual database.. If you are using SQL virtual database in your production environment, I am eager to learn more about it and your experience while using it. The ‘Virtual’ Part of virtual database When I set out to test this software, I thought virtual database had something to do with Hyper-V or visualization. In fact, the virtual database is a kind of database which shows up in your SQL Server Management Studio without actually restoring or even creating it. This tool creates a database in SSMS from the backup of the same database. The backup, however, works virtually the same way as original database. Potential Usage of virtual database: As soon as I described this tool to my teammate, I think his very first reaction was, “hey, if we have this then there is no need for log shipping.” I find his comment very interesting as log shipping is something where logs are moved to another server. In fact, there are no updates on the database from log; I would rather compare it with Snapshot Replication. In fact, whatever we use, snapshot replicated database can be similarly used and configured with virtual database. I totally believe that we can use it for reporting purpose. In fact, after this database was configured, I think the uses of this tool are unlimited. I will have to spend some more time studying it and will get back to you. Click on images to see larger images. virtual database Console Harddrive Space before virtual database Setup Attach Full Backup Screen Backup on Harddrive Attach Full Backup Screen with Settings virtual database Setup – less than 60 sec virtual database Setup – Online Harddrive Space after virtual database Setup Point in Time Recovery Option – Timeline View virtual database Summary No Performance Difference between Regular DB vs Virtual DB Please note that all SQL Server MVP gets free license of this software. Reference: Pinal Dave (http://blog.SQLAuthority.com), Idera (virtual database) Filed under: Database, Pinal Dave, SQL, SQL Add-On, SQL Authority, SQL Backup and Restore, SQL Data Storage, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, SQLAuthority News, T SQL, Technology Tagged: Idera

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• Fitting it together, database, reporting, applications in C#

  - by alvonellos

  Introduction Preamble I was hesitant to post this, since it's an application whose intricate details are defined elsewhere, and answers may not be helpful to others. Within the past few weeks (I was actually going to write a blog post about this after I finished) I've discovered that the barrier I'm encountering is one that's actually quite common for newer developers. This question is not so much about a specific thing as it is about piecing those things together. I've searched the internet far and wide, and found many tutorials on how to create applications that are kind of similar to what I'm looking for. I've also looked at hiring another, more experienced, developer to help me along, but all I've gotten are unqualified candidates that don't have the experience necessary and won't take care of the client or project like I will. I'd rather have the project never transpire than to release a solution that is half-baked. I've asked professors at my school, but they've not turned up answers to my question. I'm an experienced developer, and I've written many applications that are -- very abstractly -- close to what I'm doing, but my experiences from those applications aren't giving me enough leverage to solve this particular problem. I just hope that posting this article isn't a mistake for me to write. Project Description I have a project I'm working on for a client that is a rewrite of an application, originally written in Foxpro 2.6 by someone before me, that performs some analysis (which, sadly, I'm not allowed to disclose as per of my employment contract) on financial data. One day, after a long talk between the client and I -- where he intimately described his frustrations with all the bugs I've been hacking out of this code for 6 months now -- he told me to just rewrite it and gave me a month to write a good 1/8 of this 65k LOC Foxpro monstrosity. this 65k line of code foxpro monstrosity. It'll take me a good 3 - 6 months to rewrite this software (I know things the original programmer did not, like inheritance) going as I am right now, but I'm quickly discovering that I'm going to need to use databases. Prior to this contract I didn't even know about foxpro, and so I've had to learn foxpro on the fly, write procedures and make modifications to the database. I've actually come to like it, and this project would be rewritten in Foxpro if it were still a supported language, because over the past few months, I've come to like the features of Foxpro that make it so easy to develop data-driven applications. I once perfomed an experiment, comparing C# to Foxpro. What took me 45 minutes in C# took me two in Foxpro, and I knew C# prior to Foxpro. I was hoping to leverage the power of C#, but it intimidates me that in foxpro, you can have one line of code and be using a database. Prior to this, I have never written any serious database development from scratch. All the applications that I've written are in a different league. They are either completely data-naive or data-naive enough that I can get away with not using a database through serialization or by designing algorithms that work with the data in a manner that is stateless, so there is no need to worry about databases. I've come to realize, very quickly, that serialization and my efficacy with data structures has been my crutch all these years that's prevented me from adventuring into databases, and has consequently hindered my success in real-world programming. Sure, I've written some database stuff in Perl and Python, and I've done forms and worked with relational databases and tables, I'm a wizard in Access and Excel (seriously) and can do just about anything, but it just feels unnatural writing SQL code in another language... I don't mind writing SQL, and I don't It's that bridge between the database and the program code that drives me absolutely bonkers. I hope I'm not the only one to think this, but it bothers me that I have to create statements like the following string sSql = "SELECT * from tablename" When there's really no reason for that kind of unchecked language binding between two languages and two API's. Don't get my wrong, SQL is great, but I don't like the idea that, when executing commands on a SQL database, that one must intermix database and application software, and there's no database independence, which means that different versions of different databases can break code. This isn't very nice. The nicest thing about Foxpro is the cohesiveness between programming language and database. It's so easy, and Foxpro makes it easy, because the tool just fits the task. I can see why so many developers have created a career with this language, because it lowered the barrier of entry to data-driven applications that so many businesses need. It was wonderful. For my purposes today, with the demands and need for community support, extensibility, and language features, Foxpro isn't a solution that I feel would be the right tool for the job. I'm also worried about working too heavy with the database, because I've seen data-driven .NET applications have issues with database caches, running out of memory, and objects in the database not being collected. (Memory leaks) And OH the queries. Which one, how, and why? There are a plethora of different ways that a database can be setup, I think I counted 5 or 6 different kinds of database applications alone that I can chose from. That is a great mountain for me to climb when I don't even know where to begin when it comes to writing data-driven applications. The problem isn't that I don't know SQL or that I don't know C#. I know both and have worked with both extensively. It's making them work together that's the problem, and it's something I've never done in C# before. Reports The client likes paper. The data needs to be printed out in a format that is extensible, layered, and easy to use. I have never done reporting before, and so this is a bit of a problem. From the data source comes crystal reports, and so there's a dependency on the database, from what I understand. Code reuse A large part of the design decision that I've gone through so far is to break the task of writing a piece of this software into routines and modular DLL's and so forth such that much of the code can be reused. For example, when I setup this database, I want to be able to reuse the same database code over and over again. I also want to make sure that when the day comes that another developer is here, that he/she will be able to pick up just where I left off. The quicker I develop these applications, the better off I am. Tasks & Goals In my project, I need to write routines that apply algorithms and look for predefined patterns in financial data. Additionally, I need to simulate trading based on predefined algorithms and data. Then I need to prepare reports on that data. Additionally, I need to have a way to change the code base for this application quickly and effectively, without hacking together some band-aid solution for a problem that really needs a trauma ward. Special Considerations The solution must be fast, run quickly on existing hardware, and not be too much of a pain to maintain and write. I understand that anything I write I'm married to -- I'm responsible for the things that I write because my reputation and livelihood is dependent on it. Do I really need a database? What about performance? Performance was such a big issue that I hand wrote a data structure that is capable of performing 2 billion operations, using a total of 4 gigs of memory in under 1/4 of a second using the standard core two duo processor. I could not find a similar, pre-written data structure in C# to perform this task. What setup do I use in terms of database? What about reporting? I'd prefer to have PDF's generated, but I'd like to be able to visually sketch those reports and then just have a ReportFactory of some sort, that when I pass some variables in, it just does that data. About Me I'm a lone developer for a small business in this area. This is the first time I've done this and I've never had the breadth and depth of my knowledge tested. I'm incredibly frustrated with this project because I feel incredibly overwhelmed with the task at hand. I'm looking for that entry level point where I can draw a line and say "this is what I need to do" Conclusion I may have not been clear enough on my post. I'm still new to this whole thing, and I've been doing my best to contribute back to the community that I've leached so much knowledge from. I'd be glad to edit my post and add more information if possible. I'm looking for a big-picture solution or design process that helps me get off the ground in this world of data-driven applications, because I have a feeling that it's going to be concentric to my entire career as a programmer for some time. Specifically, if you didn't get it from the rest of the post (I may not have been clear enough) I really need some guidance as to where to go in terms of the design decisions for this project. Some things that'll be useful will be a pro/con list for the different kinds of database projects available in VS2010. I've tried, but generating that list has been as hard as solving the problem itself... If you could walk a developer writing a data-driven application for the first time in C#, how would you do that? Where would you point them to?

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• ???????/??????! Oracle Database 11g R2 ???????

  - by Yusuke.Yamamoto

  ????? ??:2010/11/17 ??:??????/?? 2009?9?? Oracle Database ?????Oracle Database 11g Release 2???????????1???????!??????????????????·??????????????????????????????????????????????????????????!??????????????????????????????????! Oracle Database 11g R2 ????Oracle Database 11g R2 ?????????? ????????? ????????????????? http://www.oracle.com/technology/global/jp/ondemand/otn-seminar/pdf/20101117_11gR2.pdf

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• Database model for keeping track of likes/shares/comments on blog posts over time

  - by gage

  My goal is to keep track of the popular posts on different blog sites based on social network activity at any given time. The goal is not to simply get the most popular now, but instead find posts that are popular compared to other posts on the same blog. For example, I follow a tech blog, a sports blog, and a gossip blog. The tech blog gets waaay more readership than the other two blogs, so in raw numbers every post on the tech blog will always out number views on the other two. So lets say the average tech blog post gets 500 facebook likes and the other two get an average of 50 likes per post. Then when there is a sports blog post that has 200 fb likes and a gossip blog post with 300 while the tech blog posts today have 500 likes I want to highlight the sports and gossip blog posts (more likes than average vs tech blog with more # of likes but just average for the blog) The approach I am thinking of taking is to make an entry in a database for each blog post. Every x minutes (say every 15 minutes) I will check how many likes/shares/comments an entry has received on all the social networks (facebook, twitter, google+, linkeIn). So over time there will be a history of likes for each blog post, i.e post 1234 after 15 min: 10 fb likes, 4 tweets, 6 g+ after 30 min: 15 fb likes, 15 tweets, 10 g+ ... ... after 48 hours: 200 fb likes, 25 tweets, 15 g+ By keeping a history like this for each blog post I can know the average number of likes/shares/tweets at any give time interval. So for example the average number of fb likes for all blog posts 48hrs after posting is 50, and a particular post has 200 I can mark that as a popular post and feature/highlight it. A consideration in the design is to be able to easily query the values (likes/shares) for a specific time-frame, i.e. fb likes after 30min or tweets after 24 hrs in-order to compute averages with which to compare against (or should averages be stored in it's own table?) If this approach is flawed or could use improvement please let me know, but it is not my main question. My main question is what should a database scheme for storing this info look like? Assuming that the above approach is taken I am trying to figure out what a database schema for storing the likes over time would look like. I am brand new to databases, in doing some basic reading I see that it is advisable to make a 3NF database. I have come up with the following possible schema. Schema 1 DB Popular Posts Table: Post post_id ( primary key(pk) ) url title Table: Social Activity activity_id (pk) url (fk) type (i.e. facebook,twitter,g+) value timestamp This was my initial instinct (base on my very limited db knowledge). As far as I under stand this schema would be 3NF? I searched for designs of similar database model, and found this question on stackoverflow, http://stackoverflow.com/questions/11216080/data-structure-for-storing-height-and-weight-etc-over-time-for-multiple-users . The scenario in that question is similar (recording weight/height of users overtime). Taking the accepted answer for that question and applying it to my model results in something like: Schema 2 (same as above, but break down the social activity into 2 tables) DB Popular Posts Table: Post post_id (pk) url title Table: Social Measurement measurement_id (pk) post_id (fk) timestamp Table: Social stat stat_id (pk) measurement_id (fk) type (i.e. facebook,twitter,g+) value The advantage I see in schema 2 is that I will likely want to access all the values for a given time, i.e. when making a measurement at 30min after a post is published I will simultaneous check number of fb likes, fb shares, fb comments, tweets, g+, linkedIn. So with this schema it may be easier get get all stats for a measurement_id corresponding to a certain time, i.e. all social stats for post 1234 at time x. Another thought I had is since it doesn't make sense to compare number of fb likes with number of tweets or g+ shares, maybe it makes sense to separate each social measurement into it's own table? Schema 3 DB Popular Posts Table: Post post_id (pk) url title Table: fb_likes fb_like_id (pk) post_id (fk) timestamp value Table: fb_shares fb_shares_id (pk) post_id (fk) timestamp value Table: tweets tweets__id (pk) post_id (fk) timestamp value Table: google_plus google_plus_id (pk) post_id (fk) timestamp value As you can see I am generally lost/unsure of what approach to take. I'm sure this typical type of database problem (storing measurements overtime, i.e temperature statistic) that must have a common solution. Is there a design pattern/model for this, does it have a name? I tried searching for "database periodic data collection" or "database measurements over time" but didn't find anything specific. What would be an appropriate model to solve the needs of this problem?

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• Examples of temporal database designs? [closed]

  - by miku

  I'm researching various database design for historical record keeping - because I would like to implement a prototypical web application that (excessively) tracks changes made by users and let them undo things, see revisions, etc. I'd love use mercurial or git as backend (with files as records) - since they already implement the kind of append-only changes I imagine. I tried git and dulwich (python git API) - and it went ok - but I was concerned about performance; Bi-temporal database design lets you store a row along with time periods, when this record was valid. This sure sound more performant than to operate on files on disk (as in 1.) - but I had little luck finding real-world examples (e.g. from open source projects), that use this kind of design and are approachable enough to learn from them. Revisions à la MediaWiki revisions or an extra table for versions, as in Redmine. The problem here is, that DELETE would take the whole history with it. I looked at NoSQL solutions, too. With a document oriented approach, it would be simple to just store the whole history of an entity within the document itself - which would reduce design plus implementation time in contrast to a RDBMS approach. However, in this case I'm a bit concerned about ACID-properties, which would be important in the application. I'd like ask about experiences about real-world and pragmatic designs for temporal data.

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• error:unknown filesystem grub rescue help

  - by Ridvan Çoban

  I'm trying to install ubuntu on my hdd which doesnt contain any operatin system, mbr or grub. (it has 3 partitions, 1st includes my data on ntfs file system, second is linux swap now, and third ex4 filesystem) Of course i don't want to lose my data on ntfs partition. Anyway i installed ubuntu on ex4 filesystem, selected sda as device for bootloader (not sda1,2 or 2). But i got error Error:unknown filesystem Grub rescue I tried ls command. It gives (hd0) , (hd,msdos1), (hd0,msdos2) and (hd0,msdos3). then tried ls (hd0)/, ls (hd0,1)/, ls (hd0,msdos2)/, ls (hd0,msdos3)/ to find the linux filesystem to boot. But i was unsuccessful. it all gave me unknown filesystem error. Am i missing or something?

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• How to design database for tests in online test application

  - by Kien Thanh

  I'm building an online test application, the purpose of app is, it can allow teacher create courses, topics of course, and questions (every question has mark), and they can create tests for students and students can do tests online. To create tests of any courses for students, first teacher need to create a test pattern for that course, test pattern actually is a general test includes the number of questions teacher want it has, then from that test pattern, teacher will generate number of tests corresponding with number of students will take tests of that course, and every test for student will has different number of questions, although the max mark of test in every test are the same. Example if teacher generate tests for two students, the max mark of test will be 20, like this: Student A take test with 20 questions, student B take test only has 10 questions, it means maybe every question in test of student A only has mark is 1, but questions in student B has mark is 2. So 20 = 10 x 2, sorry for my bad English but I don't know how to explain it better. I have designed tables for: - User (include students and teachers account) - Course - Topic - Question - Answer But I don't know how to define associations between user and test pattern, test, question. Currently I only can think these: Test pattern table: name, description, dateStart, dateFinish, numberOfMinutes, maxMarkOfTest Test table: test_pattern_id And when user (is Student) take tests, I think i will have one more table: Result: user_id, test_id, mark but I can't set up associations among test pattern and test and question. How to define associations?

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• Repair ext4 filesystem on USB drive

  - by phineas

  Yet another filesystem question. I wanted to use a USB drive that I hadn't mounted for a month or so and was surprised by the fact Ubuntu was unable to mount it. I looked it up in the disk utility and it said it discovered a device with 17 MB instead of 2 GB. The hardware looks intact, I hope for the best for repairing the ext4 filesystem. I followed the instructions from HOWTO: Repair a broken Ext4 Superblock in Ubuntu, but I wasn't successful. # fsck.ext4 -v /dev/sdb e2fsck 1.42.5 (29-Jul-2012) ext2fs_open2: Bad magic number in super-block fsck.ext4: Superblock invalid, trying backup blocks... fsck.ext4: Bad magic number in super-block while trying to open /dev/sdb The superblock could not be read or does not describe a correct ext2 filesystem. If the device is valid and it really contains an ext2 filesystem (and not swap or ufs or something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock: e2fsck -b 8193 Filesystem blocks are invalid, however when I run the recommended solution to try the alternate superblock, I get the following output: # e2fsck -b 8193 /dev/sdb e2fsck 1.42.5 (29-Jul-2012) e2fsck: Invalid argument while trying to open /dev/sdb plus the same error message as in the last paragraph above. Any ideas how to recover the drive? Thank you very much! Edit: testdisk won't help. I'm still stunned why the tools only discover 17 MB.

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• Unknown filesystem error

  - by Ben

  My computer has (had) a dual boot of Ubuntu Precise and Windows 7. Recently, when I started the computer, grub gave me an error saying "Unknown filesystem", and sent me to grub rescue. I searched for solutions to this, and found this answer: Unknown filesystem error: grub rescue. I followed the instructions there, but they didn't really help: when I restarted the computer, it went straight to Windows without grub intervening at all (so it boots successfully, just not to the OS I want). This is the log from boot-repair. My Ubuntu partition is sda6. Naturally, I'm a little worried, since the log says "unknown filesystem type ''", which to me looks like the partition might be corrupt somehow. From the Ubuntu Live CD, I started gparted and looked at my partitions, and it also told me that my sda6 is an unknown filesystem. So my questions are basically: Can I restore Ubuntu to the way it was? If not, can I at least rescue the data I had on the partition somehow? Again, if I can't restore Ubuntu, how do I clean everything up so that I can reinstall it without too many complications? Another thing I should mention is that yesterday I had a similar problem where the computer told me there was a problem with the hard drive when it was starting, but it fixed itself by running fsck (that time it got past grub, and managed to start Ubuntu). Between that occasion and me having trouble booting the computer today, I have booted it successfully at least twice. Thanks for any help!

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• usb drive filesystem?

  - by purbleguy

  So, school is approaching quickly, and one of the things on my supply list is a usb drive. Now I'm asking myself what filesystem to use. After some research, I found ext4 to be the most stable drive filesystem. But, I also found that Windows (The OS used by every computer in my school) can't read ext4 formatted drives without special drivers, and I'm sure the school wouldn't be too happy with me having to install the windows ext4 drivers on every computer I use with my usb. So, my question is, Should I use fat32, one of the ext filesystems (2, 3 or 4 would work) or NTFS, I have an ubuntu laptop, a Mac desktop, and of course the school computers I use are Windows, so which would be the best filesystem for my usb.

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• filesystem types for partitions

  - by Tim

  I am going to dual-boot install Ubuntu1 10.04 on my laptop with Windows 7. I was wondering what filesystem types (such as ext2, ext3, ext4, ReiserFS and whatever might come into mind) are recommended for various possible partitions (such as /, home, /boot, swap, and others that might come into mind)and why? if ext4 is now stable enough for use for partitions in Ubuntu and Shared partition between Windows and Ubuntu? what journaling Options (writeback, ordered and journal) are recommended for each partition's filesystem? Thanks and regards!

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• (Database Design - products attributes): What is better option for product attribute database design

  - by meyosef

  Hi, I new in database design. What is better option for product attribute database design for cms?(Please suggest other options also). option 1: 1 table products{ id product_name color price attribute_name1 attribute_value1 attribute_name2 attribute_value2 attribute_name3 attribute_value3 } option 2: 3 tables products{ id product_name color price } attribute{ id name value } products_attribute{ products_id attribute_id } Thanks, Yosef

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• Ubuntu Server Read-Only Filesystem Issue

  - by Scott Deutsch

  We are running a virtual machine server with multiple virtual machines with ubuntu server edition 12.04 and every so often (usually after updates via webmin it seems), the hard-drive turns into read-only filesystem. Only two of the virtual machines get affected by this problem (that I noticed so far). What could be causing this issue? What could we try to fix this problem? Has anyone else had this problem before? If so, what did you do to fix it? If I use Aptitude instead of webmin, it will not turn into into a read-only filesystem. Though this could be a coincidence. Could it be a webmin issue? Thanks. UPDATE 1 Looks like this is not an update/webmin issue at all. How I know this is because one of the virtual servers is a git server and it turned into a read-only filesystem out of the blue today. With this new info provided to you, what should I try? Thanks.

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• Database Vault 11gR2 11.2.0.1 Certified with Oracle E-Business Suite

  - by Steven Chan

  Oracle Database Vault allows security administrators to protect a database from privileged account access to application data.  Database objects can be placed in protected realms, which can be accessed only if a specific set of conditions are met.  Oracle Database Vault 11gR2 11.2.0.1 is now certified with Oracle E-Business Suite Release 11i and 12.You can now enable Database Vault 11gR2 on your existing E-Business Suite 11.2.0.1 Database instance.  If you already have DB Vault 10gR2 or 11gR1 enabled in your E-Business Suite environment, you can now upgrade to the 11gR2 Database.  We also support EBS patching with Database Vault 11.2.0.1 enabled. Our DB Vault realm creation and grants-related scripts have been updated to reduce patching downtimes.

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• Open source embedded filesystem (or single file virtual filesystem, or structured storage) library f

  - by Ioan

  I'm not sure what the "general" name of something like this might be. I'm looking for a library that gives me a file format to store different types of binary data in an expanding single file. open source, non-GPL (LGPL ok) C interface the file format is a single file multiple files within using a POSIX-like file API (or multiple "blobs" within using some other API) file/structure editing is done in-place reliable first, performant second Examples include: the virtual drives of a virtual machine whefs HDF CDF NetCDF Problems with the above: whefs doesn't appear to be very mature, but best describes what I'm after HDF, CDF, NetCDF are usable (also very reliable and fast), but they're rather complicated and I'm not entirely convinced of their support for opaque binary "blobs" Edit: Forgot to mention, one other relevant question: http://stackoverflow.com/questions/1361560/simple-virtual-filesystem-in-c-c Another similar question: http://stackoverflow.com/questions/374417/is-there-an-open-source-alternative-to-windows-compound-files Edit: Added condition of in-place editing.

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• Help With Database Layout

  - by three3

  Hello everyone, I am working on a site similar to Craigslist where users can make postings and sell items in different cities. One difference between my site and Craigslist will be you will be able to search by zip code instead of having all of the cities listed on the page. I already have the ZIP Code database that has all of the city, state, latitude, longitude, and zip code info for each city. Okay, so to dive into what I need done and what I need help with: 1.) Although I have the ZIP Code database, it is not setup perfectly for my use. (I downloaded it off of the internet for free from http://zips.sourceforge.net/) 2.) I need help setting up my database structure (Ex: How many different tables should I use and how should I link them) I will be using PHP and MySQL. These our my thoughts so far on how the database can be setup: (I am not sure if this will work though.) Scenario: Someone goes to the homepage and it will tell them, "Please enter your ZIP Code.". If they enter "17241" for example, this ZIP Code is for a city named Newville located in Pennsylvania. The query would look like this with the current database setup: SELECT city FROM zip_codes WHERE zip = 17241; The result of the query would be "Newville". The problem I see here now is when they want to post something in the Newville section of the site, I will have to have an entire table setup just for the Newville city postings. There are over 42,000 cities which means I would have to have over 42,000 tables (one for each city) so that would be insane to have to do it that way. One way I was thinking of doing it was to add a column to the ZIP Code database called "city_id" which would be a unique number assigned to each city. So for example, the city Newville would have a city_id of 83. So now if someone comes and post a listing in the city Newville I would only need one other table. That one other table would be setup like this: CREATE TABLE postings ( posting_id INT NOT NULL AUTO_INCREMENT, for_sale LONGTEXT NULL, for_sale_date DATETIME NULL, for_sale_city_id INT NULL, jobs LONGTEXT NULL, jobs_date DATETIME NULL, jobs_city_id INT NULL, PRIMARY KEY(posting_id) ); (The for_sale and job_ column names are categories of the types of postings users will be able to list under. There will be many more categories than just those two but this is just for example.) So now when when someone comes to the website and they are looking for something to buy and not sell, they can enter their ZIP Code, 17241, for example, and this is the query that will run: SELECT city, city_id FROM zip_codes WHERE zip = 17241; //Result: Newville 83 (Please note that I will be using PHP to store the ZIP Code the user enters in SESSIONS and Cookies to remember them throughout the site) Now it will tell them, "Please choose your category.". If they choose the category "Items For Sale" then this is the query to run and sort the results: SELECT posting_id, for_sale, for_sale_date FROM postings WHERE for_sale_city_id = $_SESSION['zip_code']; Will this work? So now my question to everyone is will this work? I am pretty sure it will but I do not want to set this thing up and realize I overlooked something and have to start from all over from scratch. Any opinions and ideas are welcomed and I will listen to anyone who has some thoughts. I really appreciate the help in advance :D

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• What filesystem for an external Harddrive (Linux/Mac/Windows)

  - by Marcel

  What Filesystem should I use for an external USB harddrive (500GB), with possibility to share with a Mac and Windows systems, for example at the office. Now it is NTFS but back in the day the NTFS support was not stable under Linux and I think it is not supported on a Mac. I would just use FAT32, but it has 4GB file size limitation, do I overlooked any other option? I looked here: filesystem types for partitions but a Mac is not mentioned. edit Windows is the least important, I am not sure if I need Windows support at all. So what would I use just for Linux and Mac?

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• Virus that makes all files and folders read-only filesystem on a usb drive

  - by ren florento

  Is there any way on how to remove a virus from Windows that makes the files and folders and the usb drive itself a read-only filesystem as this is an annoying one because the virus keeps copying itself as long as it sees a folder and keeps running which prevents you from creating and deleting files and folders from the usb drive and makes " mount -o remount,rw '/path' " ineffective ? btw i'm not really sure if it is a virus but what makes me think that it is a virus is for the reason the it creates a .exe file within every folder which was named after folder and it also immediately reverts to read-only filesystem which locks the files and folders even after executing the command " mount -o remount,rw '/path' ". i also think the virus is just running only within the usb drive as it is not affecting the folders on ubuntu. I could choose to reformat the usb drive as it only contains few important files but what concerns me is if such virus or whatever you may call it gets into my backup drives that contains many important files.Thanks for any help and advice you could give.

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• Database Memory :: MySql Innodb how much storage memory allocation for empty field vs not empty fie

  - by Yosef

  Hi, I new in database, and dont know how and when mysql allocate memory space. In MySql Innodb how much storage memory allocation for empty field (no string inserted) vs not empty field? Other form of my question: When memory allocated space In MySql Innodb for varchar/text field in time of table creation or when data inserted inside field? Thank you, Yosef

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• Block-level deduplicating filesystem

  - by James Haigh

  I'm looking for a deduplicating copy-on-write filesystem solution for general user data such as /home and backups of it. It should use online/inline/synchronous deduplication at the block-level using secure hashing (for negligible chance of collisions) such as SHA256 or TTH. Duplicate blocks need not even touch the disk. The idea is that I should be able to just copy /home/<user> to an external HDD with the same such filesystem to do a backup. Simple. No messing around with incremental backups where corruption to any of the snapshots will nearly always break all later snapshots, and no need to use a specific tool to delete or 'checkout' a snapshot. Everything should simply be done from the file browser without worry. Can you imagine how easy this would be? I'd never have to think twice about backing-up again! I don't mind a performance hit, reliability is the main concern. Although, with specific implementations of cp, mv and scp, and a file browser plugin, these operations would be very fast, especially when there is a lot of duplication as they would only need to transfer the absent blocks. Accidentally using conventional copy tools that do not integrate with the FS would merely take longer, waste some bandwidth when copying remotely and waste some CPU, as the duplicate data would be re-read, re-transferred and re-hashed (although nothing would be re-written), but would absolutely not corrupt anything. (Some filesharing software may also be able to benefit by integrating with the FS.) So what's the best way of doing this? I've looked at some options: lessfs - Looks unmaintained. Any good? [Opendedup/SDFS][3] - Java? Could I use this on Android?! What does [SDFS][4] stand for? [Btrfs][5] - Some patches floating around on mailing list archives, but no real support. [ZFS][6] - Hopefully they'll one day relicense under a true Free/Opensource GPL-compatible licence. Also, 2 years ago I had a go at an attempt in Python using Fuse at the file-level to be used over the top of a typical solid FS such as EXT4, but I found Fuse for Python underdocumented and didn't manage to implement all of the system calls. My first post here, so I can't post more than 2 links until I get over 10 rep: [3]: http://www.opendedup.org/ [4]: https://en.wikipedia.org/w/index.php?title=SDFS&action=edit&redlink=1 [5]: https://en.wikipedia.org/wiki/Btrfs#Features [6]: https://en.wikipedia.org/wiki/ZFS#Linux

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• Way(s) of browsing the filesystem that are more flexible

  - by ixtmixilix

  I have two related questions, both probably (but not necessarily preferentially) accepting the same answer : When browsing or exploring the filesystem in a GUI, I want to be able to right click on the empty space between the files, choose a menu item and say 'open terminal in this folder,' optionally as root Do the converse when using the terminal, optionally as root I use Universe with kubuntu but have Debian Lenny running with gnome installed separately, so anything on kde or gnome would work

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• SQL SERVER Retrieve and Explore Database Backup without Restoring Database Idera virtual database

  I recently downloaded Ideras SQL virtual database, and tested it. There are a few things about this tool which caught my attention.My ScenarioIt is quite common in real life that sometimes observing or retrieving older data is necessary; however, it had changed as time passed by. The full database backup was 40 GB in size, [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Transportable Database 11gR2 Certified with E-Business Suite

  - by Steven Chan

  Platform migration is the process of moving a database from one operating system platform to a different operating system platform. You might wish to migrate your E-Business Suite database to create testing instances, experiment with new architectures, perform benchmarks, or prepare for actual platform changes in your production environment. Database migration across platforms of the same "endian" format (byte ordering) using the Transportable Database (TDB) process is now certified with Oracle Database 11gR2 (11.2.0.1) for:Oracle E-Business Suite Releases 11i (11.5.10.2) Oracle E-Business Suite Release 12.0.4 or higherOracle E-Business Suite Release 12.1.1 or higherThis EBS database migration process was previously certified only for 10gR2 and 11gR1.

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• Database Trends & Applications column: Database Benchmarking from A to Z

  - by KKline

  Have you heard of the monthly print and web magazine Database Trends & Applications (DBTA)? Did you know I'm the regular columnist covering SQL Server ? For the past six months, I've been writing a series of articles about database benchmarking culminating in the latest article discussing my three favorite database benchmarking tools: the free, open-source HammerDB, the native SQL Server Distributed Replay Utility, and the commercial Benchmark Factory from Dell / Quest Software. Wondering what...(read more)

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