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• IIS 7 503 error, application pool stop crash, defdoc.dll could not be loaded due to a configuration

  - by optician

  Hi All, Currently trying to get iis 7 to work, but every time I request a page, the application pool goes into stopped status. In the event log this is what comes back. The Module DLL 'C:\Windows\System32\inetsrv\defdoc.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 processor architecture. The data field contains the error number. I've already re installed iis, any other ideas, I read that someone fixed this by downloading the dll again, but this seems like an odd solution. Thanks. EDIT I have now replaced the file with one I downloaded off the internet, and now it says The Module DLL 'C:\Windows\System32\inetsrv\protsup.dll' could not be loaded due to a configuration problem. I hope I don't have to get 100's of these.

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• windows 2003 remote desktop fail connect after windows update

  - by bookstorecowboy

  I have a number of windows servers, both win2003, win2003r2 and win2003r2 64 bit. After installing windows updates on the machines and rebooting terminal services give me an immediate "not connect" message. The servers are running fine and you can connect via the physical machine. Once you reboot the box (with remote restart in some cases when it's not accessible) terminal services behaves itself and allows a connection. Whilst it's not a show stopper it is rather annoying when you can't see your box. Anyone know why this is or what the cause is?

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• What's the value of a Facebook fan?

  - by David Dorf

  In his blog posting titled "Why Each Facebook Fan Is Worth $2,000 to J. Crew," Joe Skorupa lays out a simplistic calculation for assigning a value to social media efforts within Facebook. While I don't believe the metric, at least its a metric that can be applied consistently. Trying to explain the ROI to management to start a program, then benchmarking to show progress isn't straightforward at all. Social media isn't really mature enough to have hard-and-fast rules around valuation (yet). When I'm asked by retailers how to measure social media efforts, I usually fess-up and say I can't show an ROI but the investment is so low you might was well take a risk. Intuitively, it just seems like a good way to interact with consumers, and since your competition is doing it, you better do it as well. Vitrue, a social media management company, has calculated a fan as being worth $3.60 per year based on impressions generated in Facebook's news feed. That means a fan base of 1 million translates into at least $3.6 million in equivalent media over a year. Don't believe that number either? Fine, Vitrue now has a tool that let's you adjust the earned media value of a fan. Jump over to http://evaluator.vitrue.com/ and enter your brand's Facebook URL to get an assessment of the current value and potential value. For fun, I compared Abercrombie & Fitch (1,077,480 fans), Gap (567,772 fans), and Wet Seal (294,479 fans). The image below shows the results assuming the default $5 earned media value for a fan. The calculation is more complicated than just counting fans. It also accounts for postings and comments. Its possible for a brand with fewer fans to have a higher value based on frequency and relevancy of posts. The tool gathers data via the Social Graph API for the past 30 days of activity. I'm not sure this tool assigns the correct value either, but hey, its a great start.

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• MAXDOP in SQL Azure

  - by Herve Roggero

  In my search of better understanding the scalability options of SQL Azure I stumbled on an interesting aspect: Query Hints in SQL Azure. More specifically, the MAXDOP hint. A few years ago I did a lot of analysis on this query hint (see article on SQL Server Central:  http://www.sqlservercentral.com/articles/Configuring/managingmaxdegreeofparallelism/1029/).  Here is a quick synopsis of MAXDOP: It is a query hint you use when issuing a SQL statement that provides you control with how many processors SQL Server will use to execute the query. For complex queries with lots of I/O requirements, more CPUs can mean faster parallel searches. However the impact can be drastic on other running threads/processes. If your query takes all available processors at 100% for 5 minutes... guess what... nothing else works. The bottom line is that more is not always better. The use of MAXDOP is more art than science... and a whole lot of testing; it depends on two things: the underlying hardware architecture and the application design. So there isn't a magic number that will work for everyone... except 1... :) Let me explain. The rules of engagements are different. SQL Azure is about sharing. Yep... you are forced to nice with your neighbors.  To achieve this goal SQL Azure sets the MAXDOP to 1 by default, and ignores the use of the MAXDOP hint altogether. That means that all you queries will use one and only one processor.  It really isn't such a bad thing however. Keep in mind that in some of the largest SQL Server implementations MAXDOP is usually also set to 1. It is a well known configuration setting for large scale implementations. The reason is precisely to prevent rogue statements (like a SELECT * FROM HISTORY) from bringing down your systems (like a report that should have been running on a different in the first place) and to avoid the overhead generated by executing too many parallel queries that could cause internal memory management nightmares to the host Operating System. Is summary, forcing the MAXDOP to 1 in SQL Azure makes sense; it ensures that your database will continue to function normally even if one of the other tenants on the same server is running massive queries that would otherwise bring you down. Last but not least, keep in mind as well that when you test your database code for performance on-premise, make sure to set the DOP to 1 on your SQL Server databases to simulate SQL Azure conditions.

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• AutoVue at the Oracle Asset Lifecycle Management Summit

  - by celine.beck

  I recently had the opportunity to attend and present the integration between AutoVue and Primavera P6 during the Oracle ALM Summit, which was held in March at Redwood Shores, on Oracle Headquarters grounds. The ALM Summit brought together over 300 Oracle maintenance practitioners who endured the foggy and rainy San Francisco weather to attend the 4th edition of this Oracle-driven conference. Attendees have roles in maintenance management and IT. Following a general session, Ralph Rio from ARC Advisory Group provided a very interesting keynote session discussing Asset Management directions, both in the short and long run. An interesting point that Ralph raised is that most organizations have done a good job at improving performance at the design / build, operate and maintain and portfolio management phases by leveraging solutions like Asset Lifecycle Management and Project & Portfolio management solutions; however, there seem to be room for improvement in between those phases, when information flows from one group to the other, during the data handover phase or when time comes to update / modify drawings to reflect the reality of physical assets. This is where AutoVue comes into play. By integrating with enterprise applications like content management systems, asset lifecycle management applications and project management solutions, AutoVue can be a real-process enabler, streamlining information flows from concept/design to decommissioning and ensuring that all project stakeholders have access to asset information and engineering data throughout the asset lifecycle. AutoVue's built-in digital annotation capabilities allows maintenance workers and technicians to report changes in configuration and visually capture the delta between as-built and as-maintained versions of asset documents. This information can then be easily handed over to engineers who can identify changes and incorporate these modifications into the drawings during the next round of document revisions. PPL Power Generation, an electric utilities headquarted in Allentown, Pennsylvania discussed this usage of AutoVue during an interesting Webcast around AutoVue's role in the Utilities space. After the keynote sessions, participants broke off into product-centric tracks around Oracle's Asset Lifecycle Management solutions (E-Business Suite, PeopleSoft, and JD Edwards). The second day of the conference was the occasion for us to present the integration between AutoVue and Primavera P6 to the Maintenance Summit audience. The presentation was a great success and generated much discussion with partners and customers during breaks. People seemed highly interested in learning more about our plans for integrating AutoVue and Primavera P6 with Oracle's ALM solutions...stay tune for further information on the subject!

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• FREE Online Azure Workshop includes a **FREE Azure Account**

  - by Jim Duffy

  My friend and all around good guy, Microsoft Developer Evangelist for the Carolinas, Brian Hitney, along with fellow Microsofties Jim O’Neil and John McClelland will be presenting a FREE Windows Azure online workshop tomorrow, Tuesday, May 4th from 7pm-9pm. What? You can’t make it Tuesday evening? Not to worry. This webcast will be repeated again a number of times over the next month or so. Taken from Brian’s blog post about it: “Elevate your skills with Windows Azure in this hands-on workshop! In this event we’ll guide you through the process of building and deploying a large scale Azure application. Forget about “hello world”! In less than two hours we’ll build and deploy a real cloud app that leverages the Azure data center and helps make a difference in the world. Yes, in addition to building an application that will leave you with a rock-solid understanding of the Azure platform, the solution you deploy will contribute back to Stanford’s Folding@home distributed computing project. There’s no cost to you to participate in this session; each attendee will receive a temporary, self-expiring, full-access account to work with Azure for a period of 2-weeks.” Did you catch that last sentence??  “each attendee will receive a temporary, self-expiring, full-access account to work with Azure for a period of 2-weeks.” A FREE, full-access, Windows Azure account to experiment and learn with? Now we’re talking. For more information check out Brian’s blog post or head here. Have a day. :-|

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• iPhone Shell - is there any?

  - by alee

  While working on iphone security architecture, i came to know that i can run applications from other applications in iphone. referring to the following url http://iphonedevelopertips.com/cocoa/launching-other-apps-within-an-iphone-application.html for example, i can put a link in a website with following hyperlink skype:// will result skype to run and call at particular number. Now i have few concerns here. is there a shell running in background in iphone, so that it allows other application to run basic app commands. if the above statement is true then how can i enable or run commands directly into iphone shell? if above statements are false, then could you please explain how these commands are being executed? is this part of iPhone SDK? or this funcationality is iPhone OS

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• Technical : Configure WebCenter PS5 with WebCenter Content - Good Example

  - by Vikram Kurma

  Read Intro for this post and understand the problem here Solution  : To integrate Jdeveloper with WebCenter Content PS5 and browse through the folders , we need to enable "folders_g" features instead of "Framework Folders" . Detailed steps below . Login to Webcenter content using admin credentials https://<hostname>:<port number>/cs Go to "Administration" menu and click on "Admin Server"  In the newly opened browser , click on 'Component Manager' in the left navigation menu . On the right hand side , you should see "Advanced Component Manager" , click on it . You will now see a list of enabled and disabled features . Disable "Framework Folders" and enable "folders_g" folders . Restart the server . There you go ! . You should have a successful connection and you should be able to traverse through the contribution folders from Jdeveloper. I am posting a few pics to help you navigate the steps .    

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• ArchBeat Link-o-Rama for November 28, 2012

  - by Bob Rhubart

  Oracle BPM and Oracle Application Development Framework (ADF) | Dan Atwood Oracle ACE Dan Atwood shares an excerpt from "Oracle BPM and ADF (Part 1)," part of Avio Consulting's new self-paced online Oracle BPM Developer Workshop training. BPEL and Fire-and-Forget Web Services | Lonneke Dikmans Oracle ACE Director Lonneke Dikmans shares two use cases to illustrate the use of fire-and-forget web services. Backup and Recovery of an Exalogic vServer via rsync | Donald "On Exalogic a vServer will consist of a number of resources from the underlying machine," says the man known only as Donald. "These resources include compute power, networking and storage. In order to recover a vServer from a failure in the underlying rack all of these components have to be thoughts about. This article only discusses the backup and recovery strategies that apply to the storage system of a vServer." Making Architecture Matter | Harald Wesenberg and Einar Landre "As Architects, we want our architecture to matter. We want projects to implement our grand designs, one little step at a time, with each piece fitting perfectly into the big puzzle that is software architecture," say authors Harald Wesenberg and Einar Landre. "But reality is a bit trickier." Thought for the Day "A distributed system is one in which the failure of a computer you didn't even know existed can render your own computer unusable." — Leslie Lamport Source: SoftwareQuotes.com

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• How do I obtain a valid DNS resolution given just an IP address?

  - by Dee Newcum

  Is there a publicly-available DNS server somewhere that will respond to requests like: 74_125_225_50.anyip.com And will return 74.125.225.50 for the above request? That is, every single possible IP address can queried by name instead of number. http://ipq.co/ is close to what I'm looking for, but it requires you to first register an IP address before you can query its DNS name. I want a service that does a straightforward mapping from domain name to IP address. Why do I want to do this? I have a program that we use at work that requires a DNS lookup, but I need to be able to give it bare IP addresses. (long story... it's a server that I don't control, so I can't work around it using /etc/hosts)

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• HAProxy -- pause/queue all traffic without losing requests

  - by Marc

  I basically have the same problem as mentioned in this thread -- I would like to temporarily suspend all requests to all servers of a certain backend, so that I can upgrade the backend and the database it uses. Since this is a live system, I would like to queue up requests, and send them to the backend servers once they've been upgraded. Since I'm doing a database upgrade with the code change, I have to upgrade all backend servers simultaneously, so I can't just bring one down at a time. I tried using the tcp-request options combined with removing the static healthcheck file as mentioned in that thread, but had no luck. Setting the default "maxconn" value to 0 seems to pause and queue connections as desired, but then there seems to be no way to increase the value back to a positive number without restarting HAProxy, which kills all requests that had been queued up until that point. (The "hot-reconfiguration" options using -sf and -st start a new process, which doesn't seem to do what I want). Is what I'm trying to do possible?

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• Setup Linksys 3200 remote access

  - by Greg

  I'm trying to setup remote access for my linksys 3200 so that I can configure it through the WAN port. I have turned on remote access, however when I try to connect I get a 404 error. The settings I have are: When I try to access xxx.xxx.xxx.xxx:9999 I just get a 404 error. I have allowed RDP access to a computer behind the router and this works fine on the same IP address. Any idea's on what else I have to do to allow remote management access? UPDATE: I tried changing the port to 80 and it works. Change it back to any other number and it doesn't work. Modem is setup with a DMZ to the router's IP. Why does it only work on port 80? BTW I can't use port 80 because there is a website hosted behind the router.

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• What's a good, affortable ruter that will not give me problems when downloading torrents?

  - by Lirik

  I found several routers on newegg and they're in the $50-60 range, but I'm not sure if they'll handle the number of connections that are created when downloading torrents (100-300 seeds and around 50 peers). My roommate watches netflix movies, my brother and I download torrents, so my NETGEAR router ends up choking on the traffic and I have to restart it quite frequently. I've already posted a couple of questions on the topic and I've come to the conclusion that I need a new router. What are some routers that I should consider (my budget is in the $50 range)?

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• Differencing Disks in VirtualBox

  - by PhilPursglove

  I'm struggling to understand how to do differencing disks in VirtualBox v3.1.0. I've created a Windows 2008 Server, but now I want to use that as a base image for a number of other servers. The help file has a description of what differencing disks are, but I can't find where it actually tells you how to do it. In the Storage dialog for a server I found the Differencing Disks checkbox: but when I check it, I'd expect it to then ask which image should be the parent so I could select my base image. Any pointers you can offer would be greatly appreciated!

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• How to use nsupdate to create NAPTR record

  - by Jon Skarpeteig

  What's a working example for creating a NAPTR record using nsupdate against Bind9? man nsupdate sais: update add {domain-name} {ttl} [class] {type} {data...} Adds a new resource record with the specified ttl, class and data. But I can't seem to find the correct format for NAPTR My attempt: echo -e 'update add enum.example.com 60 IN NAPTR 1.1.1.1.1."u"."E2U+sip"."!^.*[email protected]!" .'"\nsend"|nsupdate results in: invalid rdata format: not a valid number syntax error

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• Nginx Fastcgi performance issues

  - by Barry

  I am running several fastcgi servers behind Nginx. I run 3 Nginx workers and 6 fastcgi servers as upstream backends. When I run load tests of 1 req per sec, I can clearly see that on avarage a reply is 0.1sec, but from time to time there are 3.1 sec responses. It is a suspiciously deterministic number and it happens even at very small loads from time to time. Both CPU and Memory are of no issue at all. Any idea where this delay may be comming from? Any suggestions how to debug this? Many thanks, Barry.

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• OPN Exchange @ OpenWorld – Don’t Forget…

  - by Kristin Rose

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} Mark your calendar because we’re less than a week away from kicking off our first ever Oracle PartnerNetwork Exchange @ OpenWorld program, and do we have a lot in store for you!  So don’t forget to attend these great partner events! Sunday, 9/30: The Global Partner Keynote with Judson Althoff and other senior executives @ 1:00pm OPN Exchange General Sessions  to discuss the overview of each OPN Exchange track including, Cloud, Engineered Systems, Industries, Technology and Applications @ 3:30pm The exclusive OPN Exchange AfterDark Reception complete with the smooth sounds of Macy Gray @ 7:30pm. Don’t worry, there is plenty to come after Sunday! Be sure to take part in all the exciting activity taking place during the week, including: Over 40 + OPN Exchange Sessions taking place at the Marriott Marquis throughout the week “Test Fest” exams for OPN Specialist Certifications,  taking place throughout the week The 5k Partner Fun Run- Meet at the W Hotel lobby on Monday 10/1 at 6 a.m. PT – No registration necessary! Led by Judson Althoff, SVP of WWA&C. Social Media Rally Station- Join us in the OPN Lounge on Monday to become social savvy and leverage social media tools for your business Ice Cream Social- Monday October 1st, from 3-5:30 p.m. in the OPN Lounge. Hosted by Oracle Advanced Customer Support Services. Endless Networking Opportunities at the OPN Lounge, the Howard Street Tent for lunch, the ‘It’s a Wrap Reception’, and much more! We can’t wait to see you there! The OPN Communications Team

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• How to Unban an IP properly with Fail2Ban

  - by psp

  I'm using Fail2Ban on a server and I'm wondering how to unban an IP properly. I know I can work with IPTables directly: iptables -D fail2ban-ssh <number> But is there not a way to do it with the fail2ban-client? In the manuals it states something like: fail2ban-client get ssh actionunban <IP>. But that doesn't work. Also, I don't want to /etc/init.d/fail2ban restart as that would lose all the bans in the list.

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• .NET Reflector & .NET Reflector Pro 6.1 have been released

  - by Bart Read

  .NET Reflector 6.1 and .NET Reflector Pro 6.1 have been released. You can download them from: http://www.red-gate.com/products/reflector/index.htm .NET Reflector is a class browser and disassembler for .NET assemblies. .NET Reflector Pro is a Visual Studio debugging extension that allows you to step through third party and framework assemblies, as if they were built from your own source code. This release fixes several problems that were present in the 6.0 release: Support for using a copy of Reflector.cfg stored alongside Reflector.exe has been re-enabled so users upgrading from 5.x releases will not lose their settings. Fixed unhandled exception on exit of Visual Studio when .NET Reflector add-in used in conjunction with TestDriven.NET add-in. Added better support for dealing with framework assemblies, which only contain meta-data, in the "Referenced Assemblies" folder. Fixed problem where attempted decompilation with CppCliLanguage add-in would lead to display of a page on the Red Gate website. Added option to activate .NET Reflector Pro to .NET Reflector menu in Visual Studio after receiving feedback from a number of users that it was hard to figure out how to activate the product. For more details about the products please visit: http://www.red-gate.com/products/reflector/index.htm

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• Strange. Asterisk key plays random Windows sound when pressed

  - by Charles

  This is a new one on me. When I press the "asterisk", or * button on my number pad (but not SHIFT+8), Windows makes either a "Exclamation" or "Windows ding" sound. I haven't noticed a pattern to which sound is made. Logitech K200 keyboard No special key mapping software or Logitech software running Realtek sound to stereo through optical cable. Visual Studio 2010, Chrome, Fiddler, WinRAR, Notepad++, and Dropbox running. No unusual behavior otherwise. A solution isn't terribly important but my curiosity is both piqued and stumped. This doesn't normally happen and nothing odd has taken place otherwise. Ideas?

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• Installing an EC2 (EBS based) instance on another AWS account

  - by imaginative

  We're moving from one AWS account to another. I have a couple of EC2 instances I would like to move over. These instances are EBS based. Googling around, I'm seeing all sorts of convoluted answers for how to appropriately launch this EBS based instance on a new account. Surely there has to be a simple way of going about this. As of right now, what I have done so far is backup the EB2 Volume as a snapshot. I then altered the permissions of the snapshot to allow the new AWS account number to be able to access it. I am not sure where to go from here. Do I have to create an image from the EBS snapshot? Upload it to S3? What's the next step(s)?

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• Emulate "Go to Dekstop/Home/etc." behavior in OS X via AppleScript

  - by pattulus

  OS X has build in support for going to certain Folders (Home, Utilities, Desktop, etc.) via a Shortcut. I wanted to emulate this behavior for the the Downloads Folder. The only thing that is missing the script below is that it won’t succeed when no window is opened in the Finder (see Error message). tell application "Finder" activate set target of Finder window 1 to folder "Downloads" of folder "username" of disk "Macintosh HD" end tell Error message: error "Finder got an error: Can’t set Finder window 1 to folder \"Downloads\" of folder \"username\" of disk \"Macintosh HD\"." number -10006 from Finder window 1 It great if you know about some kind of 'if-compliement' that triggers opening the Downloads Folder in case there is no window 1 open in the Finder. Thanks in advance.

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• Open the SQL Server Error Log with PowerShell

  - by BuckWoody

  Using the Server Management Objects (SMO) library, you don’t even need to have the SQL Server 2008 PowerShell Provider to read the SQL Server Error Logs – in fact, you can use regular old everyday PowerShell. Keep in mind you will need the SMO libraries – which can be installed separately or by installing the Client Tools from the SQL Server install media. You could search for errors, store a result as a variable, or act on the returned values in some other way. Replace the Machine Name with your server and Instance Name with your instance, but leave the quotes, to make this work on your system: [reflection.assembly]::LoadWithPartialName("Microsoft.SqlServer.Smo") $machineName = "UNIVAC" $instanceName = "Production" $sqlServer = new-object ("Microsoft.SqlServer.Management.Smo.Server") "$machineName\$instanceName" $sqlServer.ReadErrorLog() Want to search for something specific, like the word “Error”? Replace the last line with this: $sqlServer.ReadErrorLog() | where {$_.Text -like "Error*"} Script Disclaimer, for people who need to be told this sort of thing: Never trust any script, including those that you find here, until you understand exactly what it does and how it will act on your systems. Always check the script on a test system or Virtual Machine, not a production system. Yes, there are always multiple ways to do things, and this script may not work in every situation, for everything. It’s just a script, people. All scripts on this site are performed by a professional stunt driver on a closed course. Your mileage may vary. Void where prohibited. Offer good for a limited time only. Keep out of reach of small children. Do not operate heavy machinery while using this script. If you experience blurry vision, indigestion or diarrhea during the operation of this script, see a physician immediately. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Revocation status of DC can't be verified

  - by DotGeorge

  A Domain Controller within my forest was working fine (as the story usually goes). Then, suddenly, I can't logon with my smart card. Instead, I'm greeted with the following message: The system could not log you on. The revocation status of the domain controller certificate used for smart card authentication could not be determined. I literally have no idea what's happened here. As an attempted quick fix, I removed the root certificate which issued the Smart Card's certificate from the CA of both the client and DC. Then imported a newly exported one from the DC in question. Same issue. I've spotted a number of related articles on Microsoft's forums and a HP support document. Each don't really shed much light as it's a generic error message apparently. Having said all of this, other smart cards (issued from other DCs) work fine. So I have no idea what's up with this one.

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• Performance Optimization &ndash; It Is Faster When You Can Measure It

  - by Alois Kraus

  Performance optimization in bigger systems is hard because the measured numbers can vary greatly depending on the measurement method of your choice. To measure execution timing of specific methods in your application you usually use Time Measurement Method Potential Pitfalls Stopwatch Most accurate method on recent processors. Internally it uses the RDTSC instruction. Since the counter is processor specific you can get greatly different values when your thread is scheduled to another core or the core goes into a power saving mode. But things do change luckily: Intel's Designer's vol3b, section 16.11.1 "16.11.1 Invariant TSC The time stamp counter in newer processors may support an enhancement, referred to as invariant TSC. Processor's support for invariant TSC is indicated by CPUID.80000007H:EDX[8]. The invariant TSC will run at a constant rate in all ACPI P-, C-. and T-states. This is the architectural behavior moving forward. On processors with invariant TSC support, the OS may use the TSC for wall clock timer services (instead of ACPI or HPET timers). TSC reads are much more efficient and do not incur the overhead associated with a ring transition or access to a platform resource." DateTime.Now Good but it has only a resolution of 16ms which can be not enough if you want more accuracy.   Reporting Method Potential Pitfalls Console.WriteLine Ok if not called too often. Debug.Print Are you really measuring performance with Debug Builds? Shame on you. Trace.WriteLine Better but you need to plug in some good output listener like a trace file. But be aware that the first time you call this method it will read your app.config and deserialize your system.diagnostics section which does also take time.   In general it is a good idea to use some tracing library which does measure the timing for you and you only need to decorate some methods with tracing so you can later verify if something has changed for the better or worse. In my previous article I did compare measuring performance with quantum mechanics. This analogy does work surprising well. When you measure a quantum system there is a lower limit how accurately you can measure something. The Heisenberg uncertainty relation does tell us that you cannot measure of a quantum system the impulse and location of a particle at the same time with infinite accuracy. For programmers the two variables are execution time and memory allocations. If you try to measure the timings of all methods in your application you will need to store them somewhere. The fastest storage space besides the CPU cache is the memory. But if your timing values do consume all available memory there is no memory left for the actual application to run. On the other hand if you try to record all memory allocations of your application you will also need to store the data somewhere. This will cost you memory and execution time. These constraints are always there and regardless how good the marketing of tool vendors for performance and memory profilers are: Any measurement will disturb the system in a non predictable way. Commercial tool vendors will tell you they do calculate this overhead and subtract it from the measured values to give you the most accurate values but in reality it is not entirely true. After falling into the trap to trust the profiler timings several times I have got into the habit to Measure with a profiler to get an idea where potential bottlenecks are. Measure again with tracing only the specific methods to check if this method is really worth optimizing. Optimize it Measure again. Be surprised that your optimization has made things worse. Think harder Implement something that really works. Measure again Finished! - Or look for the next bottleneck. Recently I have looked into issues with serialization performance. For serialization DataContractSerializer was used and I was not sure if XML is really the most optimal wire format. After looking around I have found protobuf-net which uses Googles Protocol Buffer format which is a compact binary serialization format. What is good for Google should be good for us. A small sample app to check out performance was a matter of minutes: using ProtoBuf; using System; using System.Diagnostics; using System.IO; using System.Reflection; using System.Runtime.Serialization; [DataContract, Serializable] class Data { [DataMember(Order=1)] public int IntValue { get; set; } [DataMember(Order = 2)] public string StringValue { get; set; } [DataMember(Order = 3)] public bool IsActivated { get; set; } [DataMember(Order = 4)] public BindingFlags Flags { get; set; } } class Program { static MemoryStream _Stream = new MemoryStream(); static MemoryStream Stream { get { _Stream.Position = 0; _Stream.SetLength(0); return _Stream; } } static void Main(string[] args) { DataContractSerializer ser = new DataContractSerializer(typeof(Data)); Data data = new Data { IntValue = 100, IsActivated = true, StringValue = "Hi this is a small string value to check if serialization does work as expected" }; var sw = Stopwatch.StartNew(); int Runs = 1000 * 1000; for (int i = 0; i < Runs; i++) { //ser.WriteObject(Stream, data); Serializer.Serialize<Data>(Stream, data); } sw.Stop(); Console.WriteLine("Did take {0:N0}ms for {1:N0} objects", sw.Elapsed.TotalMilliseconds, Runs); Console.ReadLine(); } } The results are indeed promising: Serializer Time in ms N objects protobuf-net   807 1000000 DataContract 4402 1000000 Nearly a factor 5 faster and a much more compact wire format. Lets use it! After switching over to protbuf-net the transfered wire data has dropped by a factor two (good) and the performance has worsened by nearly a factor two. How is that possible? We have measured it? Protobuf-net is much faster! As it turns out protobuf-net is faster but it has a cost: For the first time a type is de/serialized it does use some very smart code-gen which does not come for free. Lets try to measure this one by setting of our performance test app the Runs value not to one million but to 1. Serializer Time in ms N objects protobuf-net 85 1 DataContract 24 1 The code-gen overhead is significant and can take up to 200ms for more complex types. The break even point where the code-gen cost is amortized by its faster serialization performance is (assuming small objects) somewhere between 20.000-40.000 serialized objects. As it turned out my specific scenario involved about 100 types and 1000 serializations in total. That explains why the good old DataContractSerializer is not so easy to take out of business. The final approach I ended up was to reduce the number of types and to serialize primitive types via BinaryWriter directly which turned out to be a pretty good alternative. It sounded good until I measured again and found that my optimizations so far do not help much. After looking more deeper at the profiling data I did found that one of the 1000 calls did take 50% of the time. So how do I find out which call it was? Normal profilers do fail short at this discipline. A (totally undeserved) relatively unknown profiler is SpeedTrace which does unlike normal profilers create traces of your applications by instrumenting your IL code at runtime. This way you can look at the full call stack of the one slow serializer call to find out if this stack was something special. Unfortunately the call stack showed nothing special. But luckily I have my own tracing as well and I could see that the slow serializer call did happen during the serialization of a bool value. When you encounter after much analysis something unreasonable you cannot explain it then the chances are good that your thread was suspended by the garbage collector. If there is a problem with excessive GCs remains to be investigated but so far the serialization performance seems to be mostly ok.  When you do profile a complex system with many interconnected processes you can never be sure that the timings you just did measure are accurate at all. Some process might be hitting the disc slowing things down for all other processes for some seconds as well. There is a big difference between warm and cold startup. If you restart all processes you can basically forget the first run because of the OS disc cache, JIT and GCs make the measured timings very flexible. When you are in need of a random number generator you should measure cold startup times of a sufficiently complex system. After the first run you can try again getting different and much lower numbers. Now try again at least two times to get some feeling how stable the numbers are. Oh and try to do the same thing the next day. It might be that the bottleneck you found yesterday is gone today. Thanks to GC and other random stuff it can become pretty hard to find stuff worth optimizing if no big bottlenecks except bloatloads of code are left anymore. When I have found a spot worth optimizing I do make the code changes and do measure again to check if something has changed. If it has got slower and I am certain that my change should have made it faster I can blame the GC again. The thing is that if you optimize stuff and you allocate less objects the GC times will shift to some other location. If you are unlucky it will make your faster working code slower because you see now GCs at times where none were before. This is where the stuff does get really tricky. A safe escape hatch is to create a repro of the slow code in an isolated application so you can change things fast in a reliable manner. Then the normal profilers do also start working again. As Vance Morrison does point out it is much more complex to profile a system against the wall clock compared to optimize for CPU time. The reason is that for wall clock time analysis you need to understand how your system does work and which threads (if you have not one but perhaps 20) are causing a visible delay to the end user and which threads can wait a long time without affecting the user experience at all. Next time: Commercial profiler shootout.

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