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  • Why do HDFS clusters have only a single NameNode?

    - by grautur
    I'm trying to understand better how Hadoop works, and I'm reading The NameNode is a Single Point of Failure for the HDFS Cluster. HDFS is not currently a High Availability system. When the NameNode goes down, the file system goes offline. There is an optional SecondaryNameNode that can be hosted on a separate machine. It only creates checkpoints of the namespace by merging the edits file into the fsimage file and does not provide any real redundancy. Hadoop 0.21+ has a BackupNameNode that is part of a plan to have an HA name service, but it needs active contributions from the people who want it (i.e. you) to make it Highly Available. from http://wiki.apache.org/hadoop/NameNode So why is the NameNode a single point of failure? What is bad or difficult about having a complete duplicate of the NameNode running as well?

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  • How can i install XFCE along side unity?

    - by James
    I would like to be able to install XFCE to run alongside unity so I can choose on startup which DE I use, without breaking any features of either DE. Following this: https://sites.google.com/site/easylinuxtipsproject/xubuntu "Note: don't install Nautilus in Xubuntu! This will cause system conflicts." I don't want to affect ANY of the features in unity, i.e. I want to be able to use the two interchangeably, so I can't follow some suggestions of just cleaning out all the old stuff as that would mean using unity would be changed, (http://askubuntu.com/questions/111400/can-i-install-unity-aside-with-xfce-and-switch-them-as-i-want) is this possible in 12.04? [System] ubuntu 12.04.1 64bit.

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  • What do you think about gems and eggs? Alternatives?

    - by Juanlu001
    I've read recently some criticism (see 1, 2, 3) about the packaging distribution system of two popular programming languages: Ruby gems and Python eggs. The most important argument stated against them is that they replace the system package manager (in case there is one, as in every Linux distribution), which makes eggs and gems difficult to track, code difficult to patch, and so on. Are actually eggs and gems right? In case not, are there any alternatives to distributing Python or Ruby modules? Should developers focus on taking advantage of package manager (apt-get, pacman, ...) capabilities?

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  • Is there a canonical book on general abstractions and modeling?

    - by David The Man
    I've been trying to understand the fundamentals of general abstractions and modeling: there are quite a lot of books when you search for abstractions, but most of those seem to be about learning object-oriented programming in a given language. Is there a book out there that's the de-facto standard for describing best practices, design methodologies, and other helpful information about general abstractions and modeling? What about that book makes it special?

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  • Installed fprint, can't login anymore

    - by Otto
    Tried Fprint, was stupid enough not to backup the common-auth file before changing it. Somehow I'm locked out of the system, trying to fingerscan doesn't do any difference. Even when I've done it 5 times and it asks for password, when it asks for password and I write it in and it says that it's the wrong password. I use the same password for root as for my user. Tried to go into Recovery Mode - root - sudo nano /etc/pam.d/common-auth and remove the rows saying that you need the fingerprint to login, but when I try to overwrite, it says the file is read only, even when I try to open it with root. I have a lot of schoolwork files and programs on the system, so I can't afford losing them. Help?

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  • Small hiccup with VMware Player after upgrading to Ubuntu 12.04

    The upgrade process Finally, it was time to upgrade to a new LTS version of Ubuntu - 12.04 aka Precise Pangolin. I scheduled the weekend for this task and despite the nickname of Mauritius (Cyber Island) it took roughly 6 hours to download nearly 2.400 packages. No problem in general, as I have spare machines to work on, and it was weekend anyway. All went very smooth and only a few packages required manual attention due to local modifications in the configuration. With the new kernel 3.2.0-24 it was necessary to reboot the system and compared to the last upgrade, I got my graphical login as expected. Compilation of VMware Player 4.x fails A quick test on the installed applications, Firefox, Thunderbird, Chromium, Skype, CrossOver, etc. reveils that everything is fine in general. Firing up VMware Player displays the known kernel mod dialog that requires to compile the modules for the newly booted kernel. Usually, this isn't a big issue but this time I was confronted with the situation that vmnet didn't compile as expected ("Failed to compile module vmnet"). Luckily, this issue is already well-known, even though with "Failed to compile module vmmon" as general reason but nevertheless it was very easy and quick to find the solution to this problem. In VMware Communities there are several forum threads related to this topic and VMware provides the necessary patch file for Workstation 8.0.2 and Player 4.0.2. In case that you are still on Workstation 7.x or Player 3.x there is another patch file available. After download extract the file like so: tar -xzvf vmware802fixlinux320.tar.gz and run the patch script as super-user: sudo ./patch-modules_3.2.0.sh This will alter the existing installation and source files of VMware Player on your machine. As last step, which isn't described in many other resources, you have to restart the vmware service, or for the heart-fainted, just reboot your system: sudo service vmware restart This will load the newly created kernel modules into your userspace, and after that VMware Player will start as usual. Summary Upgrading any derivate of Ubuntu, in my case Xubuntu, is quick and easy done but it might hold some surprises from time to time. Nonetheless, it is absolutely worthy to go for it. Currently, this patch for VMware is the only obstacle I had to face so far and my system feels and looks better than before. Happy upgrade! Resources I used the following links based on Google search results: http://communities.vmware.com/message/1902218#1902218http://weltall.heliohost.org/wordpress/2012/01/26/vmware-workstation-8-0-2-player-4-0-2-fix-for-linux-kernel-3-2-and-3-3/ Update on VMware Player 4.0.3 Please continue to read on my follow-up article in case that you upgraded either VMware Workstation 8.0.3 or VMware Player 4.0.3.

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  • How to install my current Ubuntu based OS on to an external drive? [closed]

    - by Godel Fishbreath
    Possible Duplicate: How do I install Ubuntu to a USB key? How to copy an Ubuntu install from one laptop to another I have found urls to install ubuntu to a HD. But my current system has been upgraded and updated so often that it does not resemble anything on the web or on my drive disks. So giving my a url to how to install ubuntu will fail. Give me instead 'how to install my current Linux/Ubuntu based system (11.04) and all the upgrades to my external HD. Or alternately how to back up the OS into a bootable external HD. I am looking for either urls or a very complete explanation.

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  • HP mini 5102 Ethernet does not work after suspend on Lubuntu 12.10

    - by Marcin
    Ethernet works fine after system is rebooted The onboard card is seen in 'lspci' as: 43:00.0 Ethernet controller: Marvell Technology Group Ltd. Yukon Optima 88E8059 [PCIe Gigabit Ethernet Controller with AVB] (rev 11) After system being suspended the sky2 driver loads but does not enable the NIC. I have noticed that it happens when PC is left suspended for longer period of time (few houres) Trying to reproduce it I have tried to load the sky2 driver with 'modprobe sky2'. Unfortunately typing 'ifconfig -a' for the onboard ethernet adapter does not list the driver once the sky2 driver is loaded. I have searched internet and I found some information about a bug in kernel. Hovewer it was reported in 2010 so I hope it has been fixed. Here it is http://lists.opensuse.org/opensuse-bugs/2010-02/msg01473.html

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  • Restart Trouble Ubuntu 12.10

    - by Cristi
    I`ve installed Ubuntu 12.10 on 3 different machines: Acer AspireOne Netbook Lenovo T60 Notebook Desktop - P5P77 - Asus mainboard - I3 - porcessor I have the same issue on all of themm they won`t restart (Shut Down work), I can see the proceses are killed but it freezez on black screen total iresponsive. Even when I access the bios config to modify something then Save&Exit then restart I get the same thing. This is the same for all 3 machines. I also cleaned up the desktop system, last version of bios update, full HDD format, fresh win7 installed (practicly no trace of the old Ubuntu 12.10) still the same problem. Some time ago I had Ubuntu 11.10 on the desktop system, it worked perfectly. I also mention that I tried all combinations of ACPI settings in BIOS, unfortunately with no results. Please advice, I am a little desperate :)) Best regards, Cristian, Romania

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  • Oracle University New Courses (Week 12)

    - by swalker
    Oracle University released the following new (versions of) courses recently: Database Oracle Enterprise Manager Cloud Control 12c: Install & Upgrade (2 days) Using Oracle Enterprise Manager Cloud Control 12c Introduction to Big Data (1 day seminar) Introduction to Oracle NoSQL Database (1 day seminar) Oracle Database Administration I: Certification Exam Preparation Seminar (Training On Demand) Development Tools Oracle Database SQL: Certification Exam Preparation Seminar (Training On Demand) MySQL MySQL for Beginners (4 days) Fusion Middleware Oracle Service Bus 11g: System Admin, Design & Integrate Accelerated (5 days) Oracle WebLogic Server 11g: Administration Essentials (Training On Demand) Oracle Solaris Developing and Deploying Applications on Oracle Solaris 11 (3 days) Fusion Applications Fusion Applications: Installation and Administration (4 days) E-Business Suite R12.x Oracle E-Business Suite Essentials for Implementers (Training On Demand) R12.x Implement Oracle Workflow (Training On Demand) R12.x Oracle Applications System Administrator Fundamentals (Training On Demand) PeopleSoft PeopleSoft PeopleTools I Rel 8.50 (Training On Demand) Get in contact with your local Oracle University team for more details and course dates. Stay Connected to Oracle University: LinkedIn OracleMix Twitter Facebook Google+

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  • How do you handle unfound resources?

    - by concept3d
    For example your game expects a certain asset to be loaded what is the best way to handle it if the resource isn't found, for example: Texture* grassTexture = LoadTexture("Grass.png");// returns NULL as texture is not found. Mesh* car = LoadMesh("Car.obj");// returns NULL as 3d mesh is not found What if for some reason the resource wasn't found e.g. deleted by user, misspelling while in development ? Should I use Assertions (which is only useful while in development? Exit the game gracefully ? or even thrown an exception and try to handle it? On a separate question, if I used a handle system instead of pointers (which I am already working on) I don't see how this would help me recover from unfound resources, Does a handle system help in situations like this?

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  • Unable to start backuppc

    - by iUngi
    I had a ext4 drive today I replaced with a RAID drive, I moved all the files from the old HDD. After that I tried to start the Backuppc but I'm getting the following error: Can't create a test hardlink between a file in /media/WESYS_RAID/backups/nbackuppc/pc and /media/WESYS_RAID/backups/nbackuppc/cpool. Either these are different file systems, or this file system doesn't support hardlinks, or these directories don't exist, or there is a permissions problem, or the file system is out of inodes or full. Use df, df -i, and ls -ld to check each of these possibilities. Quitting... The permission looks like this: drwxrwxrwx 2 backuppc backuppc 4096 2012-04-12 11:06 cpool -rwxrwxrwx 1 backuppc backuppc 14290 2012-04-10 16:00 dead.letter drwxrwxrwx 2 backuppc backuppc 4096 2012-04-12 10:56 log drwxrwxrwx 2 backuppc backuppc 4096 2012-04-12 11:08 pc drwxrwxrwx 2 backuppc backuppc 4096 2011-10-27 22:40 pool drwxrwxrwx 2 backuppc backuppc 4096 2011-10-27 22:40 trash I also tried to create hardlinks and it does work ln -i test.txt testlink The result of the df -i Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sdc 122101760 1279684 120822076 2% /media/WESYS_RAID /dev/mapper/WeSyS_LVM 115687424 308565 115378859 1% /media/WESYS_LVM What am I doing wrong?

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  • Why would I learn C++11, having known C and C++?

    - by Shahbaz
    I am a programmer in C and C++, although I don't stick to either language and write a mixture of the two. Sometimes having code in classes, possibly with operator overloading, or templates and the oh so great STL is obviously a better way. Sometimes use of a simple C function pointer is much much more readable and clear. So I find beauty and practicality in both languages. I don't want to get into the discussion of "If you mix them and compile with a C++ compiler, it's not a mix anymore, it's all C++" I think we all understand what I mean by mixing them. Also, I don't want to talk about C vs C++, this question is all about C++11. C++11 introduces what I think are significant changes to how C++ works, but it has introduced many special cases that change how different features behave in different circumstances, placing restrictions on multiple inheritance, adding lambda functions, etc. I know that at some point in the future, when you say C++ everyone would assume C++11. Much like when you say C nowadays, you most probably mean C99. That makes me consider learning C++11. After all, if I want to continue writing code in C++, I may at some point need to start using those features simply because my colleagues have. Take C for example. After so many years, there are still many people learning and writing code in C. Why? Because the language is good. What good means is that, it follows many of the rules to create a good programming language. So besides being powerful (which easy or hard, almost all programming languages are), C is regular and has few exceptions, if any. C++11 however, I don't think so. I'm not sure that the changes introduced in C++11 are making the language better. So the question is: Why would I learn C++11? Update: My original question in short was: "I like C++, but the new C++11 doesn't look good because of this and this and this. However, deep down something tells me I need to learn it. So, I asked this question here so that someone would help convince me to learn it." However, the zealous people here can't tolerate pointing out a flaw in their language and were not at all constructive in this manner. After the moderator edited the question, it became more like a "So, how about this new C++11?" which was not at all my question. Therefore, in a day or too I am going to delete this question if no one comes up with an actual convincing argument. P.S. If you are interested in knowing what flaws I was talking about, you can edit my question and see the previous edits.

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  • does not boot after install, my troubleshooting and google fu have failed me

    - by chris
    I can only get an install to "stick" if I use shred to zerofill my drive first. Otherwise, when I install ubuntu or lubuntu 12.04, I will get "grub rescue: out of disk". With the aforementioned (completely default) install on top of a zerofilled drive, then rebooting after installing updates will tell me there is no operating system. I don't even get to grub. Installing on top of the failed install, while choosing "erase ubuntu 12.04 and reinstall", I get the grub rescue: out of disk error. The hard drive has been repeatedly tested and does not have any read or write errors. I've used check disk for errors on the pen drive I'm installing from and it comes up clean as well. The system is an inspiron 6000, with 1gb ram and a 250 gb hard drive. I'm typing this from a live cd on the same machine. What gives?

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  • Certification Notes: 70-583 Designing and Developing Windows Azure Applications

    - by BuckWoody
    Last Updated: 02/01/2011 It’s time for another certification, and we’ve just release the 70-583 exam on Windows Azure. I’ve blogged my “study plans” here before on other certifications, so I thought I would do the same for this one. I’ll also need to take exam 70-513 and 70-516; but I’ll post my notes on those separately. None of these are “brain dumps” or any questions from the actual tests - just the books, links and notes I have from my studies. I’ll update these references as I’m studying, so bookmark this site and watch my Twitter and Facebook posts for when I’ll update them, or just subscribe to the RSS feed. A “Green” color on the check-block means I’ve done that part so far, red means I haven’t. First, I need to refresh my memory on some basic coding, so along with the Azure-specific information I’m reading the following general programming books: Introducing Microsoft .NET (Pro-Developer): link   Head First C#, 2E: A Learner's Guide to Real-World Programming with Visual C# and .NET: link Microsoft Visual C# 2008 Step by Step: link  c The first place to start is at the official site for the certification. link c On that page you’ll find several resources, and the first you should follow is the “Save to my learning” so you have a place to track everything. Then click the “Related Learning Plans” link and follow the videos and read the documentation in each of those bullets. There are six areas on the learning plan that you should focus on - make sure you open the learning plan to drill into the specifics. c Designing Data Storage Architecture (18%) Books I’m Reading: Links: My Notes: c Optimizing Data Access and Messaging (17%) Books I’m Reading: Links: My Notes: c Designing the Application Architecture (19%) Books I’m Reading: Applied Architecture Patterns on the Microsoft Platform: link Links: My Notes: c Preparing for Application and Service Deployment (15%) Books I’m Reading: Links: My Notes: c Investigating and Analyzing Applications (16%) Books I’m Reading: Links: My Notes: c Designing Integrated Solutions (15%) Books I’m Reading: Applied Architecture Patterns on the Microsoft Platform (2nd mention) Links: My Notes:

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  • Should I keep investing into data structures and algorithms?

    - by 4bu3li
    These days, I'm investing heavily in data structures and algorithms and trying to solve some programming puzzles. I'm trying to code and solve with Java and Clojure. Am I wasting my time? should I invest more in technologies and frameworks that I already know in order to gain deeper knowledge (the ins and the outs) and be able to code with them more quickly? By studying data structures and algorithms, am I going to become a better programmer or those subjects are only important during college years?

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  • Xerox 3100 mfp printer/ scanner not working not working

    - by Nikos
    I have installed the latest version of Ubuntu on my system. My problem is I cannot find the proper drivers for my printer/ scanner:Xerox Phaser 3100 MFP. Although it is recognised by the system and my print jobs appear as completed, in fact they are not. Also I have a problem with my wireless connectio. Although it is configured in the network settings, connection is not successful, unless I restart my router. What can I do? Thank you in advance

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  • Problem with NVIDIA G86 on Kubuntu 12.04

    - by Stefan
    I got problems some weeks ago with my NVIDIA G86 (8500 GT), supposedly due to the infamous 295.40 version of the driver. I got errror messges like NVRM: RmInitAdpterFailed. Tried varous sugestions about setting kernel acpi and memory options, but no luck. I pulled in x-swat and got 302.17, if I remember correctly. It did not help. People recommended xorg-edgers , so I pulled that in and got kernel 3.5.0.12 and nvidia 304.43 but the problem remained. Getting slightly panicked, I tried to back back to vanilla 12.04, so I purged nvidia* and located and removed anything on the system that smelled nvidia. I installed nouveau, cause people said it was great, but as it turns out, my card does not seem to be supported. :-( Sigh... So now I fear that I have atmessed up system, and graphics is terrible. Any help would be appreciated. Xorg.0.log: http://paste.ubuntu.com/1189616/ kern.log: http://paste.ubuntu.com/1189634/

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  • Delay command execution over sockets

    - by David
    I've been trying to fix the game loop in a real time (tick delay) MUD. I realized using Thread.Sleep would seem clunky when the user spammed commands through their choice of client (Zmud, etc) e.g. east;south;southwest would wait three move ticks and then output everything from the past couple rooms. The game loop basically calls a Flush and Fill method for each socket during each tick (50ms) private void DoLoop() { Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); while (running) { // for each socket, flush and fill ConnectionMonitor.Update(); stopWatch.Stop(); WaitIfNeeded(stopWatch.ElapsedMilliseconds); stopWatch.Reset(); } } The Fill method fires the command events, but as mentioned before, they currently block using Thread.Sleep. I tried adding a "ready" flag to the state object that attempts to execute the command along with a queue of spammed commands, but it ends up executing one command and queuing up the rest i.e. each subsequent command executes something that got queued up that should've been executed before. I must be missing something about the timer. private readonly Queue<SpammedCommand> queuedCommands = new Queue<SpammedCommand>(); private bool ready = true; private void TryExecuteCommand(string input) { var commandContext = CommandContext.Create(input); var player = Server.Current.Database.Get<Player>(Session.Player.Key); var commandInfo = Server.Current.CommandLookup .FindCommand(commandContext.CommandName, player.IsAdmin); if (commandInfo != null) { if (!ready) { // queue command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo }); return; } if (queuedCommands.Count > 0) { // queue the incoming command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo, }); // dequeue and execute var command = queuedCommands.Dequeue(); command.Info.Command.Execute(Session, command.Context); setTimeout(command.Info.TickLength); return; } commandInfo.Command.Execute(Session, commandContext); setTimeout(commandInfo.TickLength); } else { Session.WriteLine("Command not recognized"); } } Finally, setTimeout was supposed to set the execution delay (TickLength) for that command, and makeReady just sets the ready flag on the state object to true. private void setTimeout(TickDelay tickDelay) { ready = false; var t = new System.Timers.Timer() { Interval = (long) tickDelay, AutoReset = false, }; t.Elapsed += makeReady; t.Start(); // fire this in tickDelay ms } // MAKE READYYYYY!!!! private void makeReady(object sender, System.Timers.ElapsedEventArgs e) { ready = true; } Am I missing something about the System.Timers.Timer created in setTimeout? How can I execute (and output) spammed commands per TickLength without using Thread.Sleep?

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  • Extending the Value of Your Oracle Financials Applications Investment with Document Capture, Imaging and Workflow

    Learn how Oracles end-to-end document imaging system extends the value and increases the automation of your Oracle Financials applications by using intelligent capture and imaging technologies to streamline high volume operations like accounts payable. Oracle Imaging and Process Management 11g (Oracle I/PM 11g) offers an integrated system that digitizes paper invoices, intelligently extracts header information and line item details, initiates automated workflows, and enables in-context access to imaged invoices directly from Oracle Applications, including Oracle E-Business Suite Financials and PeopleSoft Enterprise Financial Management. Come hear more about these certfied, standards-based application integrations as well as how document imaging can help your organization achieve quick, measurable ROI, by increasing efficiencies across financial departments, and reducing costs related to paper storage and handling.

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  • Writing a Master's Thesis on evaluating visual scripting systems

    - by user1107412
    I am thinking to write my Master's thesis around theorizing, and then implementing a PlayMaker or Kismet-like (building game logic by visually arranging FSMs) tool in Unity. The only thing I am still concerned about is the actual research question that I should pose. I was kinda hoping that the more experienced game designers out there might know. Update: What about reducing the use of visual programming to graphically designing FSM-Action-Transition flows, which can then be attached to game entities (very much like http://playmaker.com does it)?

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  • Configuring trace file size and number in WebCenter Content 11g

    - by Kyle Hatlestad
    Lately I've been doing a lot of debugging using the System Output tracing in WebCenter Content 11g.  This is built-in tracing in the content server which provides a great level of detail on what's happening under the hood.  You can access the settings as well as a view of the tracing by going to Administration -> System Audit Information.  From here, you can select the tracing sections to include.  Some of my personal favorites are searchquery,  systemdatabase, userstorage, and indexer.  Usually I'm trying to find out some information regarding a search, database query, or user information.  Besides debugging, it's also very helpful for performance tuning. [Read More] 

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  • Configuring trace file size and number in WebCenter Content 11g

    - by Kyle Hatlestad
    Lately I've been doing a lot of debugging using the System Output tracing in WebCenter Content 11g.  This is built-in tracing in the content server which provides a great level of detail on what's happening under the hood.  You can access the settings as well as a view of the tracing by going to Administration -> System Audit Information.  From here, you can select the tracing sections to include.  Some of my personal favorites are searchquery,  systemdatabase, userstorage, and indexer.  Usually I'm trying to find out some information regarding a search, database query, or user information.  Besides debugging, it's also very helpful for performance tuning. One of the nice tricks with the tracing is it honors the wildcard (*) character.  So you can put in 'schema*' and gather all of the schema related tracing.  And you can notice if you select 'all' and update, it changes to just a *.   To view the tracing in real-time, you simply go to the 'View Server Output' page and the latest tracing information will be at the bottom. This works well if you're looking at something pretty discrete and the system isn't getting much activity.  But if you've got a lot of tracing going on, it would be better to go after the trace log file itself.  By default, the log files can be found in the <content server instance directory>/data/trace directory. You'll see it named 'idccs_<managed server name>_current.log.  You may also find previous trace logs that have rolled over.  In this case they will identified by a date/time stamp in the name.  By default, the server will rotate the logs after they reach 1MB in size.  And it will keep the most recent 10 logs before they roll off and get deleted.  If your server is in a cluster, then the trace file should be configured to be local to the node per the recommended configuration settings. If you're doing some extensive tracing and need to capture all of the information, there are a couple of configuration flags you can set to control the logs. #Change log size to 10MB and number of logs to 20FileSizeLimit=10485760FileCountLimit=20 This is set by going to Admin Server -> General Configuration and entering them in the Additional Configuration Variables: section.  Restart the server and it should take on the new logging settings. 

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