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• Using DEBUG Mode in Oracle SQL Developer to Log SQL

  - by thatjeffsmith

  Curious how we’re getting the data you see in SQL Developer when you click on something? While many of the dialogs provide a ‘SQL’ panel that shows you the SQL ABOUT to be generated, I’d rather see the SQL AS it’s executed. True, you could set a TRACE or fire up a Monitor Sessions report, but both of those solutions leave me hungry for more. Did you know that SQL Developer has a ‘debug’ mode? It slows the tool down a bit and spits out a lot of information you don’t care about, but it ALSO shows you ALL the SQL that is sent to the database, as you click around the tool! See ALL the SQL that SQL Developer sends to the database on your behalf Enable DEBUG Mode When you see the splash screen as SQL Developer fires up, frantically hit Up, Up, Down, Down, Left, Right, Left, Right, B, A, SELECT, Start. Wait, wrong game. No, all you need to do is go to your SQL Developer directory and navigate down to the ‘bin’ directory. In that directory, find the ‘sqldeveloper.conf’ file. Install Directory - sqldeveloper - bin - sqldeveloper.conf Open it with a text editor. Find this line IncludeConfFile sqldeveloper-nondebug.conf And replace it with this line IncludeConfFile sqldeveloper-debug.conf Save the file. Start up SQL Developer. Observe the Logging Page – Log Panel for the SQL There’s going to be more than just SQL here. You’ll actually see a LOT of other information. If you’re having general problems with the tool and you want to see the nitty-gritty of what’s going on, then this is a good place to satisfy your curiosity and might help us diagnose your issue if you post to the forums or open a ticket with My Oracle Support. You’ll find ‘INFO’ entries that look a little something like this - This is the query used to populate your Tables list in the connection tree. You can double-click on the sql text and get a pop-up window that’s much easier to read. See all that typing we’re saving you? I don’t recommend running in DEBUG mode all the time. Capturing this information and displaying it is more expensive than not doing so. And it provides a lot of information you don’t normally need to see. But when you DO want to know what’s going on and why, this is an excellent way of getting that information. When you’re ready to go back to ‘normal’ mode, just close SQL Developer, go back to your .conf file, and add the ‘nondebug’ bit back.

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• View the Real Links Behind Shortened URLs in Chrome

  - by Asian Angel

  When you encounter shortened URLs there is always that worry in the back of your mind about where they really lead to. Now you can get a “sneak peak” at the real links behind those URLs with the View Thru extension for Google Chrome. The URL Shortening services officially supported at this time are: bit.ly, cli.gs, ff.im, goo.gl, is.gd, nyti.ms, ow.ly, post.ly, su.pr, & tinyurl.com. Before When you encounter a shortened URL you are pretty much on your own in deciding whether to trust that link or not. It would really be nice if you could just hover your mouse over those links and know where they will lead ahead of time. After Once you have the extension installed you are ready to access that link viewing goodness. Please note that you will need to reload any pages that were open prior to installing the extension. For our first example we chose a shortened URL from “bit.ly”. As you can see the entire link behind the shortened URL is displayed very nicely…no hidden surprises there! Note: There are no options to worry with for the extension. Another perfect result for the “goo.gl URL” shown below. View Thru will certainly remove a lot of the stress related to clicking on shortened URLs. Bonus Find Just out of curiosity we looked for a shortened URL not listed as being officially supported at this time. We found one with the “http://nyti.ms/” domain and View Thru showed the link perfectly…so be sure to give it a try on other services too. Conclusion If you worry about where a shortened URL will really lead you then the View Thru extension can help alleviate that stress. Links Download the View Thru extension (Google Chrome Extensions) Similar Articles Productive Geek Tips See Where Shortened URLs “Link To” in Your Favorite BrowserVerify the Destinations of Shortened URLs the Easy WayCreate Shortened goo.gl URLs in Google Chrome the Easy WayCreate Shortened goo.gl URLs in Your Favorite BrowserAccess Google Chrome’s Special Pages the Easy Way TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 QuicklyCode Provides Cheatsheets & Other Programming Stuff Download Free MP3s from Amazon Awe inspiring, inter-galactic theme (Win 7) Case Study – How to Optimize Popular Wordpress Sites Restore Hidden Updates in Windows 7 & Vista Iceland an Insurance Job?

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• SQL Prompt Easter Egg

  - by Johnm

  Having Red Gate's SQL Prompt installed with SQL Server Management Studio has saved me many headaches over the years of its use. It is extremely nice to type in a table name and see not only the column names, but also their data types and identification of primary keys. Another cool feature is the built-in short cut scripts that are included toward the bottom of the suggestion box. An example of these short cut scripts would be to type in the letters  cv and then hit enter and the following template for CREATE VIEW will appear: CREATE VIEW --WITH ENCRYPTION, SCHEMABINDING, VIEW_METADATA AS     SELECT /* query specification */ -- WITH CHECK OPTION GO These scripts are great, and on occasion rather humorous. Recently, I was writing an UPDATE statement that would update a derived and aliased set of data in . An example of such a statement is as follows: UPDATE y SET a.[FieldA] = b.[FieldB] FROM     (         SELECT             a.[FieldA]             ,b.[FieldB]         FROM             [MyTableA] a             INNER JOIN [MyTableB] b                 ON a.[PKA] = b.[PKB]     ) y; Upon typing the UPDATE y portion I hit enter and the expression "A A A A R G H !" appeared resulting in an unexpected burst of laughter. With a dash of curiosity and a pinch of research I discovered that at the bottom of the SQL Prompt suggestion box resides a short cut script called "yell", which is described as "Vent your frustration". Another humorous short cut script is "neo", which is described as "-- I know Kung-Fu". All is required for these to activate is to type the first letter and hit enter. I wonder if there are any undocumented ones?

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• Redgate ANTS Performance Profiler

  - by Jon Canning

  Seemingly forever I've been working on a business idea, it's a REST API delivering content to mobiles, and I've never really had much idea about its performance. Yes, I have a suite of unit tests and integration tests, but these only tell me that it works, not how well it works. I was also about to embark on a major refactor, swapping the database from MongoDB to RavenDB, and was curious to see if that impacted performance at all, so I needed a profiler that supported IIS Express that I can run my integration tests against, and Google gave me:   http://www.red-gate.com/supportcenter/content/ANTS_Performance_Profiler/help/7.4/app_iise   Excellent. Following the above guide an instance of IIS Express and is launched, as is Internet Explorer. The latter eventually becomes annoying, I would like to decide whether I want a browser opened, but thankfully the guide is wrong in that it can be closed and profiling will continue. So I ran my tests, stopped profiling, and was presented with a call tree listing the endpoints called and allowing me to drill down to the source code beneath.     Although useful and fascinating this wasn't what I was expecting to see, I was after the method timings from the entire test suite. Switching Show to Methods Grid presented me with a list of my methods, with the slowest lit up in red at the top. Marvellous.     I did find that if you switch to Methods Grid before Call tree has loaded, you do not get the red warnings.   StructureMap was very busy, and next on the list was a request filter that I didn't expect to be so overworked. Highlighting it, the source code was presented to me in the bottom window with timings and a nice red indicator to show me where to look. Oh horror, that reflection hack I put in months ago, I'd forgotten all about it. It was calling Validate<T>() which in turn was resolving a validator from StructureMap. Note to self, use //TODO: when leaving smelly code lying around.     Before refactoring, remember to Save Profile Results from the File menu. Annoyingly you are not prompted to save your results when exiting, and using Save Project will only leave you thankful that you have version control and can go back in time to run your tests again.   Having implemented StructureMap’s ForGenericType, I ran my tests again and:     Win, thankyou ANTS (What does ANTS stand for BTW?)   There's definitely room in my toolbox for a profiler; what started out as idle curiosity actually solved a potential problem. When presented with a new codebase I can see enormous benefit from getting an overview of the pipeline from the call tree before drilling into the code, and as a sanity check before release it gives a little more reassurance that you've done your best, and shows you exactly where to look if you haven’t.   Next I’m going to profile a load test.

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• Training v. Teaching

  - by Chris Gardner

  Originally posted on: http://geekswithblogs.net/freestylecoding/archive/2014/05/28/training-v.-teaching.aspxAs some of you may know, I recently accepted a position to teach an undergraduate course at my alma mater. Yesterday, I had my first day in an academic classroom. I immediately noticed a difference with the interactions between the students. They don't act like students in a professional training or conference talk. I wanted to use this opportunity to enumerate some of those differences. The immediate thing I noticed was the lack of open environment. This is not to say the class was hostile towards me. I am used to entering the room, bantering with audience, loosening everyone a bit, and flowing into the discussion. A purely academic audience does not banter. At least, they do not banter on day one. I think I can attribute this to two factors. This first is a greater perception of authority. In a training or conference environment, I am an equal with the audience. This is true even if I am being a subject matter expert. We're all professionals. We're all there to learn from each other, share our stories, and enjoy the journey. In the academic classroom, there was a distinct class difference. I had forgotten about this distinction; I had the professional familiarity with the staff by the time I completed my masters. This leads to the other distinction. These was an expectation of performance. At conference and professional training, there is generally no (immediate) grading. This may be a preparation for a certification exam, but I'm not the one responsible for delivering the exam. This was not the case in the academic classroom. These students are battling for points, and I am the sole arbiter. These students are less likely to let the material wash over them, applying the material to their past experiences. They were down taking notes. I don't want to leave the impression that there was no interact in the classroom. I spent a good deal of time doing problems with the class on the whiteboard. I tried to get the class to help me work out the steps. This opened up a few of them. After every conference or training class, I always get a few people that will email me afterward to continue the conversation. I am very curious to see if anybody comes to my office hours tomorrow. However, that is a curiosity that will have to wait until tomorrow.

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• NSclient++ NRPE issues

  - by Kyle

  I have had NSclient++ working with Nagios for a while now. Recently I started testing Nagwin just to see how it would work, out of pure curiosity. I stopped checking a test server with my main Nagios config, set NSclient++ to NRPE mode, and pointed Nagwin at it. It worked great for a few hours then suddenly I started seeing "UNKNOWN: No Handler for that command." I figured it has to be Nagwin's fault since it's so new, I'll just unload NRPElistner.dll and return my server to being monitored by check_NT. However now check_NT doesn't work my main Nagios server returns timeout errors and is unable to connect at all. My Nagwin server can connect to it, the server just doesn't know how to handle the check_NRPE commands even though it did with no changes a few hours earlier. I have been working on this for a day now and am fairly certain it is NSclient++ who is to blame here. My nagwin box has successfully stayed connected to a similar server throughout the night, without any issues. And my main Nagios config is not having any problems at all. I have been able to successfully switch another server between being monitored by nagios and nagwin without any problems by simply loading and unloading the NRPE.dll. I have tried uninstalling NSclient++ and reinstalling with fresh configuration but still receive the errors. As of now the firewall is off on the server, NSclient++ is setup to accept connection from any server, there is no password, I have also turned ssl off, and the NRPE module is loaded. Any Ideas would be appreciated, I am not an advanced Nagios user but I do know my way around it and can easily break it down and set it up again. I also want to add that while in test mode NSclient++ is unable to handle check_NRPE commands there either.

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• Why did MAC-Adress Cloning Fix My Router?

  - by FranticPedantic

  I have a Belkin router, and about a year ago, I suddenly lost my internet connectivity from Comcast. The internet worked fine when I plugged it right into my laptop, so I just ignored it. When I moved to another apartmnet I eventually took the dive and called tech support. The tech told me to clone my MAC address which completely fixed the issue. Now I know what a MAC address is and I've read what MAC cloning is. What has bothered me since is that I don't see how this fixed the issue. As I have understood MAC address cloning, it has the router pretend it has the same MAC address as my computer. Here is why I don't understand why this fixes my issue: I have used several different computers with this router. Cloning the MAC address fixed it for ALL of my computers. The laptop I first used with my ISP was not the one that I eventually had connected when I cloned the address. Furthermore, I didn't have any problems for quite some time after I stopped using the first computer. It wasn't like the internet suddenly stopped working when I changed which laptop I was using Now it occurred to me that maybe there was some sort of expiration? Except... Which MAC address did it clone? It was just an option in the router administration page. Did it just pick whichever computer was connected to it? If my ISP still wanted the MAC of my first computer, how did some other computer's fix it? As mentioned earlier, why did this problem seemingly stem from nowhere? Anyway, I don't have any current problems so this is more just out of general curiosity. If anybody can explain it, it would be appreciated!

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• Server Performance

  - by sb12

  I know very little about performance tuning of servers etc... so i thought i'd put this up here as i start some research on it, just to get some direction. I am in the process of migrating from my old server to a new one - both are 64 bit machines. One is a few years old, the other brand new (PowerEdge R410). The old server spec is: 2 cpus, 3.4GHz Pentiums, 8G of RAM, Fedora 11 currently installed The new server spec is: 16 cpus, 3.2 GHz Xeon, 16G of RAM, CentOS 6.2 installed. Also RAID10 is on the new server - no RAID on the old one. Both servers currently have the same database (MySQL) with the same data migrated. I wrote a Perl script that simply steps through each row of a table in the database (about 18000 rows) and updates a value in that row. Every row in the table is updated. Out of curiosity i ran this perl script on both machines, just to see how the new server would perform vs. the old one, and it produced interesting results: The old server was twice as fast as the new one to complete. Looking at the database, both are configured exactly the same (the new one being a dump of the old one...)... Anyone any ideas why this would be given the hardware gap between both? As i said i'm about to start some digging, but thought i'd put this up here to maybe get some good direction.... Many thanks in advance..

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• Apache ProxyPassReverse and https

  - by joshuaball

  Hi, I would like to map all traffic on 80 and 443 from foo.com to an internal server: 192.168.1.101. I have a VirtualHost (Apache 2.2 on Ubuntu) setup as follows (note, I had to break up the hyperlinks below because I am a 'new user'): <VirtualHost *:80> ServerName foo.com ServerAlias *.foo.com ProxyRequests Off ProxyPreserveHost On <Proxy *> Order deny,allow Allow from all </Proxy> ProxyPass / http://192.168.1.101/ ProxyPassReverse / http://192.168.1.101/ </VirtualHost> And that works great for http traffic. However, I can't seem to do the same thing for https. I have tried: Changing VirtualHost *:80 to * - but that doesn't work (I need it http-http and https-https) Creating a new VirtualHost entry for *:443 that redirects to http://192.168.1.101/, but that fails as well (browser timeouts) I did some searching, here and elsewhere, and the closest question I could find was this, but that didn't quite answer it. Also, just out of curiosity, I tried mapping all ports to https (by changing the two ProxyPass lines from http to https (and removing the :80 from VH), and that didn't work either. How would you do that as well? Any thoughts? Thanks in advance.

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• Difference between accessing a website using Local host and IP address

  - by Cdeez

  I have developed an ASP.NET website and deployed into my IIS server. Now to see that my IIS is installed fine, I type local host in my address bar, and I get the welcome screen of IIS and its documentation in a separate window. Now I gave the url of my website http://localhost/mysites/site2/Default.aspx I access my site. Also giving my IP address instead of local host like: http://192.168.1.46/mysites/site2/Default.aspx also works. Just out of curiosity I wanted to see what happens when I give my IP address in addressbar. It asks me a user name and password saying:The server 192.168.1.46:80 requires a user name and password. I donot know what user name and password it is asking, and as of my knowledge I thought localhost points to my own IP address internally. But what is the difference and also what username and password do I need for it? Update: On chrome and IE just giving localhost displays the welcome screen, but on mozilla, localhost is also asking for a username and password.

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• How do I determine the cause of a sustained spike in mysql queries/activity?

  - by mattmcmanus

  So this is more of a "I'm trying to learn about how this works" question rather than "there is a serious problem I can't figure out!" question. I'm setting up a VPS and have been tweaking and changing things here and there. I recently installed munin (like two days ago) and yesterday I noticed a significant increase in mysql activity. So now my curiosity is going crazy. How do I setup/access mysql's query log? I have about 5 databases on the server so I want to see which one is getting all the action. Is there anything else I can do to keep a better eye on what's going on? Here are the graphs. As you can tell, it's not that much activity at all but I'm just curious at the change. The sites that are on the server right now do not get a lot of traffic. It's running a couple drupal sites, only one of which is live. The live one hasn't had a spike in traffic and the last spike was 250 visitors so it's barely a spike at all.

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• What determines what resolutions a laptop is willing to output over VGA?

  - by Joshua McKinnon

  I'm responsible for several conference rooms and have setup 1080p projectors and I provide both HDMI and VGA connectivity. HDMI for DisplayPort and Mini-DisplayPort, and VGA as a fallback, universal option. Contrary to what I expected, people seem to have much more trouble with the HDMI than VGA, so VGA gets used a lot more than you'd think (even as most workstation laptops made in the last 3-4 years have DisplayPort or Mini-DisplayPort...). Also to my surprise, VGA outputs over 1080p on a 50ft cable run with very minimal degradation on certain laptops - other laptops just don't offer 1080p as a resolution choice and top out at 1600x1200 or something else. Specific example: a ThinkPad W530 will do 1080p, a W520 won't, over VGA. (both do 1080p over displayport/mini-DP) What determines what resolutions a laptop is willing to output over VGA? I'm thinking this will come down to either a video driver that says it supports only certain resolutions for output, or limitations of the RAMDAC (which wouldn't be in play, at least DAC wise, on a digital output, but WOULD on VGA, an analog output). The basic reason for the question is that I noticed, say, a ThinkPad W520 with 1080p built in display, will output 1080p fine over DisplayPort to a 1080p projector, but will cap out at 1600x1200 (practically the same pixel count, just a little shy) on VGA. Now, this wouldn't be surprising at all except SOME laptops have no issue outputting 1080p over VGA, even with lower native resolutions. Why do I care? Well if there's some way I could enable it... for situations where my users end up using VGA anyway, it's preferable for display mirroring if they can output their laptop's native resolution, which, you guessed it, is very often 1080p on 15" models. DISCLAIMER: This is primarily a curiosity, I'm not claiming 1080p over VGA is ideal by any means, but hey, if it works. I've seen HDMI start artifacting more over same-length, same gauge cabling (up to 50' run in certain rooms). If you think this is better suited to SuperUser, please move it, but this is framed from an IT standpoint of something that affects a real pool of users in a multiple conference room, 50+ deployed laptop scenario.

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• Find out the type of an automounted device

  - by Steve Bennett

  I'm working on a system (Ubuntu Precise) with a mount defined in /etc/fstab as follows: /dev/vdb /mnt auto defaults,nobootwait,comment=cloudconfig 0 2 Originally I just wanted to find out if it's NFS (due to potential MySQL locking issues). Judging from man mount, it's not: If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. Mount uses the blkid library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g., devpts, proc and nfs). If /etc/filesystems ends in a line with a single * only, mount will read /proc/filesystems afterwards. But, out of curiosity now, how can I find out more about what type of device it actually is? (For context, this is a VM running on OpenStack. The device is a 60Gb allocation mounted from somewhere - but I don't know how.)` EDIT Including answers here: $ mount /dev/vdb on /mnt type ext3 (rw,_netdev) $ df -T /dev/vdb ext3 61927420 2936068 55845624 5% /mnt

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• How flexible is the 'indirect' function?

  - by Chuck

  My curiosity pushes me to ask this question. If I were to have a series of functions that referenced a different column in a worksheet but all ended on the same row of data is there a way to point the 'row' part of a cell reference to a blank cell and use it has a variable to show the results of the functions up to a desired row simultaneously? Example: =Average('worksheet 1'.$A$1:'worksheet 1'.$A100) =Max('worksheet 1'.$B$1:'worksheet 1'.$B100) =Min('worksheet 1'.$C$1:'worksheet 1'.$C100) =Sum('worksheet 1'.$D$1:'worksheet 1'.$D100) Pseudo formulas... =Average('worksheet 1'.$A$1:'worksheet 1'.$A*('worksheet 2'.$A$1)*) =Max('worksheet 1'.$B$1:'worksheet 1'.$B*('worksheet 2'.$A$1)*) =Min('worksheet 1'.$C$1:'worksheet 1'.$C*('worksheet 2'.$A$1)*) =Sum('worksheet 1'.$D$1:'worksheet 1'.$D*('worksheet 2'.$A$1)*) Where 'worksheet 2'.$A$1 would only contain a number corresponding to a row in 'worksheet 1'. After stumbling upon and playing with the indirect() function I have only been able to replace the entire cell reference (Column and Row) with any success. The formula so far =SUM('worksheet 1'.C3:INDIRECT(A1)) Where A1 is on 'worksheet 2' and contains a full cell reference pointing to 'worksheet 1'. Any pointers?

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• Excluding files from web logs

  - by Ray

  I originally tried this question on StackOverflow, but it was suggested that serverfault was a better choice. So, here it is... Looking through my web logs, I see a lot of entries that don't interest me. Some of them are commonly used images, css files, and scripts, which I can easily exclude by un-checking the 'log visits' check box in IIS for the folder properties. I would also like to exclude log entries for certain common requests which are not in their own folders. Mostly, 'favicon.ico'. 'scriptresource.axd', and 'webresource.axd'. These (especially scriptresource.axd) make up almost a third of a typical log file on my site. So, the question is, how do I tell IIS not to log these requests? And is there any reason that this is a bad idea? The purpose of doing this is to reduce the log file size and the amount of work the server has to do, to make the log file more manageable when I need to dig in to them for troubleshooting, and for my own curiosity. I realize that log file parsers can skip the junk, but I am interested in reducing the raw files, before parsing.

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• Does MySQL log successful or attempted queries?

  - by Nathan Long

  I'm trying to track down a hit-or-miss bug in a web application. Sometimes a request completes just fine; sometimes it hangs and never finishes. I see that Apache now has several requests listed on the server-status page as "sending reply," and that doesn't change. I'm testing on localhost, so there shouldn't ever be more than one. Out of curiosity, I set MySQL to log all queries and I'm tail -fing the log file. When things go OK, I see a pattern like this: 20 Connect root@localhost on dbname 20 Query (some query #1) 20 Query (some query #2) (etc) 20 Quit 21 Connect (etc) When it hangs, I see a pattern like this: 22 Connect root@localhost on dbname 22 Query (some query #1) //nothing happens, so I try the post again 23 Connect root@localhost on dbname 23 Query (some query #1) //nothing happens; try again 24 Connect (etc) Here's my question: is MySQL logging attempted queries, or successful queries? In other words, if the last line I see is query #1, does that imply that query #1 or query #2 is hanging? My guess is that the one I don't see is the problem, because the last one I see looks fine, but maybe the one I don't see is too screwed-up for MySQL to process. Thoughts?

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• Outlook certificate error and separate send/receive error

  - by Richard

  I run a laptop with Vista 32bit and MS Office 2010. Outlook has two profiles, both configured as POP3/SMTP and neither go through an exchange server. Recently, one of the mail servers (hosted with easily) was getting full, so I changed the profile setting to delete from the server if mails are older than 60 days. Suddenly, I am now experiencing a couple of glitches. The first is that I get a certificate error when outlook tries it's first send/receive under the relevant profile - "The server you are connected to is using a security certificate that cannot be verified" This continues despite apparently successfully re-importing the certificate. The second glitch is that I get a "Sending reported error (0x8004010F): 'Outlook data file cannot be accessed'" error on send receive. Strangely, it seems to be trying to send/receive twice - once to 'mail@domain', which works, and the second to 'domain' which doesn't. I've tried deleting the profile and re-creating it, pointing to the original .pst file, but still get both errors. Does anybody know how I can resolve these errors? (As a by note, and not that important, more for curiosity, does anybody know why simply changing the delete from server setting against that profile would cause these issues?)

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• Will a 2.4Ghz WAP intefere with a 5.0Ghz WAP if placed directly next to each other

  - by Dan

  This is mostly a curiosity question to people who know more about radio and wi-fi than I. The 2.4Ghz band is massively overpopulated near my house to the point of sometimes getting 1000ms pings to the router from only a few feet away. inSSIDer finds at least 10 broadcasting SSID's within around 15 seconds of starting, so this isn't a real surprise to me! Sometimes I can get good results by changing the channel to something like 3 or 8, but it's usually temporary as the others use Auto Channel and hop around. Now, the router I have is capable of 5.0Ghz, as is the laptop I type this on. Switching to 5.0Ghz gives superb results: I can download at ~90Mbps and get consistent 1ms pings. The problem is that only this laptop supports 5.0Ghz! My question: Would I still get decent 5.0Ghz performance if I place a 2.4Ghz access point directly next to my router? And, indeed, will 2.4Ghz continue working as 'normal'? Testing would be an obvious step, but I threw all my superfluous equipment out in a recent house move. My understanding is that I should get good performance, certainly in comparison to having two devices using the same frequency range, but I do believe there will be some impact by the virtue of them being directly next to each other. (Cabling is not an option due to it being a rented house)

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• What's the piece of hardware listening on Facebook's or Wikipedia's IP address?

  - by Igor Ostrovsky

  I am trying to understand how massive sites like Facebook or Wikipedia work, for my intellectual curiosity. I read about various techniques for building scalable sites, but I am still puzzled about one particular detail. The part that confuses me is that ultimately, the DNS will map the entire domain to a single IP address, or a handful of IP addresses in the case of round-robin DNS. For example, wikipedia.org has only one type-A DNS record. So, people from all over the world visiting Wikipedia have to send a request to the one IP address specified in DNS. What is the piece of hardware that listens on the IP address for a massive site, and how can it possibly handle all the load coming from the requests for users all over the world? Edit 1: Thanks for all the responses! Anycast seems like a feasible answer... Does anyone know of a way to check whether a particular IP address is anycast-routed, so that I could verify that this really is the trick used in practice by large sites? Edit 2: After more reading on the topic, it appears that anycast is not typically used for dynamic web content. Anycast is usually used for UDP (e.g., DNS lookups), or sometimes for static content. One interesting thing to note is that Facebook uses profile.ak.fbcdn.net to host static content like style sheets and javascript libraries. Each time I ping this name, I get a response from a different IP address. However, I can't tell whether this is anycast in action, or a completely different technique. Back to my original question: as far as I can tell, even a large site will have a single expensive piece of load-balancing hardware listening on its handful of public IP addresses.

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• In an environment with multiple WiFi access points, do wireless clients sometimes connect to both at the same time?

  - by Bobby Burgess

  This is more of a curiosity than a problem, but in this new office I have two D-link DAP-2553's connected in a master/slave array (this just means the master keeps certain configuration options aligned with the slave). The network is set to 802.11n-only, and each AP has the same SSID and WPA2 key. The only difference is that they are on different channels (1 and 11). The WiFi network itself is working well. Users can roam around and the signal/speed is fairly consistent. However, I notice that when I look at the 802.11 client list in the web admin page for each of the 2 APs, I see that certain clients are connected to both, for extended periods of time, but I assume they are only passing data through one of them. Not every client is seen on each AP, but at any given time the same MAC address of a WiFi adapter can be associated (and remain associated) with both APs. The client list auto-refreshes every few seconds so I believe I'm looking at the most recent rather than stale information. One of the WiFi adapters that consistently associates with both APs is an Intel Centrino Wireless-N 1030 (laptop chip). Is it part of the WiFi standard that more than one association per WiFi card can be established concurrently on separate APS?

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• Legalities of freelance security consultant (SQLi) [closed]

  - by Seidr

  Over the years I've gained a large amount of experience in Programming (my main occupation) and server admin, and as a result have a fairly decent backing in security practices. I'm also pretty good at spotting security flaws in software (including but not limited to SQLi), and have built up a list of sites that could definately use some looking at. My question is, what are the legalities of me contacting these sites saying something along the lines of "I've looked at your site and it appears vulnerable - customer data could be compromoised - would you like me to fix it?". Could me finding out that the site is infact vulnerable be construed as an attack itself? If the prospective client so wished, could they take me to court over this? When I find a vulnerable site, all I do is confirm and make a note of the vulnerability. I'm not in it for personal gain (getting paid for FIXING it would be nice!), just curiosity. Is this a viable way to go about finding clients for this kind of work, or would you recommend a more 'legitimate' way? Any suggestions/advice would be greatly appreciated :)

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• Unexpected(?) high 'wasted' memory in memcached

  - by Nanne

  Looking at our memcached stats I think I have found an issue I was not aware of before. It seems that we have a strangely high amount of wasted space. I checked with phpmemcacheadmin for a change, and found this image staring at me: Now I was under the impression that the worst-case scenario would be that there is 50% waste, although I am the first to admit not knowing all the details. I have read - amongst others- this page which is indeed somewhat old, but so is our version of memcached. I think I do understand how the system works (e.g.) I believe, but I have a hard time understanding how we could get to 76% wasted space. The eviction rate that phpmemcacheadmin shows is 2 ev/s, so there is some problem here. The primary question is: what can I do to fix this. I could throw more memory at it (there is some extra available I think), maybe I should fiddle with the slab config (is that even possible with this version?), maybe there are other options? Upgrading the memcached version is not a quickly available option. The secondairy question, out of curiosity, is of course if the rate of 75% (and rising) wasted space is expected, and if so, why. System: This is currently not something I can do anything about, I know the memcached version isn't the newest, but these are the cards I've been dealt. Memcached 1.4.5 Apache 2.2.17 PHP 5.3.5

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• Why does my microwave kill the Wi-Fi?

  - by Ohlin

  Every time I start the microwave in the kitchen, our home Wi-Fi stops working and all devices lose connection with our router! The kitchen and the Wi-Fi router are in opposite ends of the apartment but devices are being used a little here and there. We've been annoyed by the instability of the Wi-Fi for some time and it wasn't until recently we realized it was correlated to microwave usage. After some testing with having the microwave on and off we could narrow down the problem to only occurring when the router is in b/g/n mode and uses a set channel. If I change to b/g mode or set channel to auto then there is no problem any more...but still! The router is a Zyxel P-661HNU ("802.11n Wireless ADSL2+ 4-port Security Gateway" with latest firmware) and the microwave is made by Neff with an effect of 1000W (if this information might be useful to anyone). There is an "internet connection" light on the router and it doesn't go out when the interruption occurs so I think this is only an internal Wi-Fi issue. Now to my questions: What parts of the Wi-Fi can possibly be affected by the microwave usage? Frequency? Disturbances in the electrical system? How can setting Auto on channels make a difference? I thought the different channels were just some kind of separation system within the same frequency spectrum? Could this be a sign that the microwave is malfunctioning and slowly roasting us all at home? Is there any need to be worried? Since we were able to find router settings that cooperate well with our microwave's demand for attention, this question is mainly out of curiosity. But as most people out there...I just can't help the fact that I need to know how it's possible :-)

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• 85 Hz on old/new driver looks the same like 75 Hz on previous one?

  - by jon

  I have old philips 107T5 CRT and Nvidia graphics card. I used old Nvidia driver (but it wasn't 'legacy' one when I installed it) for few years but recently I decided to install other Linux distribution. I used 75 Hz refresh rate and 1024x768 resolution on my previous distribution. After I installed the new distribution I had to install a Nvidia driver so I downloaded one from the Nvidia site (this time only legacy supported my card so I downloaded legacy and installed it). It wasn't automatically updating xorg.conf but I had my previous xorg.conf copy and I used it. When I run X I could only choose 85 and 75 Hz, 85 was checked as default. And now what shocks me: that default 85 Hz looks identically like 75 Hz on previous driver looked (at least to me). I tried 75 Hz out of curiosity and it's too bright, hurts, etc. But on the previous driver 75 Hz wasn't hurting my eyes. Why is it different? It's the same number after all, so it should always give the same results, right? That's my first question. Second question: Is 85 Hz OK for that monitor model? Would it break it? I tried to find the optimal refresh rate for this model but couldn't find it.

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• Intel Motherboard Lightning Victim Dies Hard

  - by Stetson RDT

  Today, I have a more hardware-related question. I have an Intel board, and I really do not know which board it is, I built the machine for a relative, but he forgot to keep the documentation. Long story short, the computer was disconnected during a lightning storm, but a lightning strike travelled in via the ethernet cable (It was directly connected to a power brick commonly seen on those long distance ISP Wireless transmitters), and the motherboard was shocked. I am attempting to get this PC going. The problem is as follows: The computer will randomly reboot, just in the middle of anything as it pleases. May load to EFI (or whatever BIOS is nowadays), may load to bootloader, may even get to the OS. But before 5 minutes is up, the system will always die. Out of curiosity, I plugged my voltmeter in to a molex connector. On the 5V side, it gets a good, consistant +5.13V. On the 12V side, it fluctuates, as follows: Upon immediate startup, it soars to 12.11-12.13V. It will now do one of two things: it will immediately jump down to 12.04-12.05V, or hover for about a minute at 12.11-12.13, then jump down. It seems the longer the voltage stays at 12.11-12.13, the shorter the machine will stay running. Also, post codes, whenever the machine locks up, but does not die hard, seem to be between "AA" and "AC". Does this make any sense to anybody? Do you all think this motherboard is salvageable? It was an expensive bugger, and I'd prefer to not replace it.

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