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• Windows - Delayed Write Failed error on USB hard drive

  - by ndngrd

  I've got a new Verbatim 1.5TB USB hard drive (Samsung HD154UI) and I'm finding myself completely unable to fill it. I'm using Windows XP. Whenever I try to copy a load of files over, it works for some time (will copy over between 20 and 90GB) but eventually stops with an error saying "The specified path is too deep" - the specified is not too deep, there's nothing more than 2 dirs deep that I'm copying. A balloon pops up at the bottom saying "Windows - Delayed Write Failed" telling me the data could not be copied. This wouldn't be too bad if I could just restart the transfer, but after this error has happened I can't write anything else to the disk - including if I eject it and then connect it to another machine. It just seems completely locked. The only way I can unlock it is to delete everything that I was copying to it. I've tried various USB cables and copying from different machines, and the same thing keeps happening.

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• Which particular file caused "Delayed write failed" error?

  - by user35020

  I sometimes get this error when resuming from hibernation: Delayed Write Failed: Windows was unable to save all the data for the file G:\$Mft. The data has been lost. This error may be caused by a failure of your computer hardware or network connection. Please try to save this file elsewhere. I know this is caused because the hard drive (G:, an external USB drive) was (a) plugged in when I hibernated and wasn't ready at wake-up, or (b) I simply forgot to plug it when resuming from hibernation. My question is: is there any way to see which particular file/folder/etc failed to be written? The hard drive functions correctly before and after, so there seems to be no permanent damage. Is there a detailed log someplace or a utility? I've searched but found nothing. Thanks for any help!

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• Delayed internet access

  - by Joel Coel

  When I (and presumably my users) first start up or log in to my computer I can't get internet access until several minutes after logging in. Internet pages like serverfault.com will time out. During this time I can access internal web servers. Sometimes pinging the gateway seems to fix the problem. I'm using Windows 7 on this machine with wifi, and the problem seems limited to the wifi network, which is on a separate vlan. The wired network does not share the problem, but I know it's not the wifi connection itself because the internal sites work. The wifi access point is attached to a 3Com 4200 switch, with the port set for vlan 2 untagged, vlan 1 tagged. The 4200 has a fiber connection to a 3Com 4900SX fiber switch that acts almost as a router here. The fiber connection is vlan 1 untagged vlan 2 tagged at both ends. The gateway is then attached to a different 4200 (vlan 1 untagged, vlan 2 tagged) that has a similar fiber connection to the 4900SX. vlan 2 has 192.168.8.0/22 IPs, vlan 1 has 10.1.0.0/16 IPs. The 4900SX has an interface for both vlans (10.1.1.1/192.168.8.1), as does the gateway (10.1.1.5/192.168.8.5). There is one dchp server for both vlans on the same switch as the gateway. It chooses a dhcp scope based on the interface used by the 4900sx to forward the dhcp request. There is also a network access list on the 4900sx set to deny all vlan2 traffic to any 10.1.x.x host, with exceptions made for a few servers, including dhcp, 4900sx, and the gateway. I think that about covers it. Any ideas on why internet access would be delayed like this?

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• Delayed_job not executing the perform method but emptying the job queue

  - by James

  I have a fresh rails 3 app, here's my Gemfile: source 'http://rubygems.org' gem 'rails', '3.0.0' gem 'delayed_job' gem 'sqlite3-ruby', :require = 'sqlite3' Here's the class that represents the job that I want to queue: class Me < Struct.new(:something) def perform puts "Hello from me" logger.info "Hello from me" logger.debug "Hello from me" raise Exception.new end end From the console with no workers running: irb(main):002:0> Delayed::Job.enqueue Me.new(1) => #<Delayed::Backend::ActiveRecord::Job id: 7, priority: 0, attempts: 0, handler: "--- !ruby/struct:Me \nsomething: 1\n", last_error: nil, run_at: "2010-12-29 07:24:11", locked_at: nil, failed_at: nil, locked_by: nil, created_at: "2010-12-29 07:24:11", updated_at: "2010-12-29 07:24:11"> Like I mentioned: there are no workers running: irb(main):003:0> Delayed::Job.all => [#<Delayed::Backend::ActiveRecord::Job id: 7, priority: 0, attempts: 0, handler: "--- !ruby/struct:Me \nsomething: 1\n", last_error: nil, run_at: "2010-12-29 07:24:11", locked_at: nil, failed_at: nil, locked_by: nil, created_at: "2010-12-29 07:24:11", updated_at: "2010-12-29 07:24:11">] I start a worker with script/delayed_job run The queue gets emptied: irb(main):006:0> Delayed::Job.all => [] However, nothing happens as a result of the puts, nothing is logged from the logger calls, and no exception is raised. I'd appreciate any help / insight or anything to try.

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• Weird exception with delayed_job

  - by Tam

  Trying to queue a job with delayed_job as follows: Delayed::Job.enqueue(BackgroundProcess.new(current_user, object)) current_user and object are not nil when I print them out. The weird thing is that sometimes refreshing the page or running the command again works! Here is the exception trace: Delayed::Backend::ActiveRecord::Job Columns (44.8ms) SHOW FIELDS FROM `delayed_jobs` TypeError (wrong argument type nil (expected Data)): /Users/.rvm/rubies/ruby-1.9.1-p378/lib/ruby/1.9.1/yaml.rb:391:in `emit' /Users/.rvm/rubies/ruby-1.9.1-p378/lib/ruby/1.9.1/yaml.rb:391:in `quick_emit' /Users/.rvm/rubies/ruby-1.9.1-p378/lib/ruby/1.9.1/yaml/rubytypes.rb:86:in `to_yaml' vendor/plugins/delayed_job/lib/delayed/backend/base.rb:65:in `payload_object=' activerecord (2.3.9) lib/active_record/base.rb:2918:in `block in assign_attributes' activerecord (2.3.9) lib/active_record/base.rb:2914:in `each' activerecord (2.3.9) lib/active_record/base.rb:2914:in `assign_attributes' activerecord (2.3.9) lib/active_record/base.rb:2787:in `attributes=' activerecord (2.3.9) lib/active_record/base.rb:2477:in `initialize' activerecord (2.3.9) lib/active_record/base.rb:725:in `new' activerecord (2.3.9) lib/active_record/base.rb:725:in `create' vendor/plugins/delayed_job/lib/delayed/backend/base.rb:21:in `enqueue'

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• Emails from Google Apps to custom SMTP server delayed by 1 hour consistently

  - by vimalk

  The outgoing mails from Google Apps/Gmail to our own custom SMTP server are getting delayed by 1 hour consistently. mxtoolbox.com diagnostics of our custom SMTP server are looking OK. Our custom SMTP server is receiving emails from other sources (yahoo, hotmail etc.) on time. Looking at the SMTP logs show a delay in a google intermediate SMTP server. Received: by qwi2 with SMTP id 2so1989393qwi.3 for <[email protected]>; Thu, 27 Jan 2011 03:54:23 -0800 (PST) MIME-Version: 1.0 Received: by 10.224.19.203 with SMTP id c11mr1587082qab.170.1296125657457; Thu, 27 Jan 2011 02:54:17 -0800 (PST) This setup has been working fine for a year though our custom email server was missing a reverse DNS entry and SPF records. Thinking that this could be the cause of the issue, we added these entries a week ago. But the issue still persists. Here are are more details: We are using Google Apps to host our primary domain email (say: mydomain.com) The custom SMTP server (say: s1.mydomain.com) hosts our subdomain (say: sub.mydomain.com) This is how the email log looks from [email protected] to [email protected] Return-Path: [email protected] Received: from localhost.localdomain (LHLO s1.mydomain.com) (127.0.0.1) by s1.mydomain.com with LMTP; Thu, 27 Jan 2011 17:24:28 +0530 (IST) Received: from localhost (localhost.localdomain [127.0.0.1]) by s1.mydomain.com (Postfix) with ESMTP id 605116A6565 for <[email protected]>; Thu, 27 Jan 2011 17:24:28 +0530 (IST) X-Virus-Scanned: amavisd-new at sub.mydomain.com X-Spam-Flag: NO X-Spam-Score: 2.984 X-Spam-Level: ** X-Spam-Status: No, score=2.984 tagged_above=-10 required=6.6 t ests=[AWL=-0.337, BAYES_50=0.001, DNS_FROM_OPENWHOIS=1.13, FH_DATE_PAST_20XX=3.188, HTML_MESSAGE=0.001, HTML_OBFUSCATE_05_10=0.001, RCVD_IN_DNSWL_LOW=-1] autolearn=no Received: from s1.mydomain.com ([127.0.0.1]) by localhost (s1.mydomain.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id RBjF7Wwr44mP for <[email protected]>; Thu, 27 Jan 2011 17:24:24 +0530 (IST) Received: from mail-qw0-f44.google.com (mail-qw0-f44.google.com [209.85.216.44]) by s1.mydomain.com (Postfix) with ESMTP id BB5DE6A6512 for <[email protected]>; Thu, 27 Jan 2011 17:24:23 +0530 (IST) Received: by qwi2 with SMTP id 2so1989393qwi.3 for <[email protected]>; Thu, 27 Jan 2011 03:54:23 -0800 (PST) MIME-Version: 1.0 Received: by 10.224.19.203 with SMTP id c11mr1587082qab.170.1296125657457; Thu, 27 Jan 2011 02:54:17 -0800 (PST) Received: by 10.220.117.17 with HTTP; Thu, 27 Jan 2011 02:54:17 -0800 (PST) Date: Thu, 27 Jan 2011 16:24:17 +0530 Message-ID: <[email protected]> Subject: test : 16:24 From: X <[email protected]> To: [email protected] Content-Type: multipart/alternative; boundary=0015175cba2865a5fe049ad1c5cd We appreciate any help that could help solve this issue :)

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• Websockets Server with Fault-Tolerance and Durable Message Store

  - by smitchell360

  I am starting to experiment with websockets. Does anyone know of a websockets server (open source or paid) that provides a durable store of the websocket "channel"? All of the examples that I have found do not address durability -- if a websockets server goes down, all "channel" data is lost. Services such as Pusher do not really discuss whether they address the durability issue (and I have not received a response from tech support yet). Happy to roll my own, but would rather not reinvent the wheel. EDIT: I'm not looking for websockets 101 information. That is readily available and understood. I'm looking for a server (open source or paid) that supports websockets and has a durable store for the websocket data so that, in the event that a server fails, a new server can take over where the original one left off. Two main purposes: 1. support failover scenarios contemplated by the websockets Network Working Group http://tools.ietf.org/html/draft-ibc-websocket-dns-srv-02#section-5.1 (most importantly so that missed messages are sent when a client connects to a failover server) 2. support scenarios where new subscribers must receive all past messages that were published. Of course this can be handled at the application layer...but that is not what I am looking for. EDIT So, after some research the following installed options seem to be the most robust: Kaazing Migratory Migratory (http://migratory.ro) Hosted services that seem "real" Pusher (great API but no history feature yet) PubNub (has history) All of the above services have graceful fallback to other communication methods if websockets are not available. I was not able to find any open source that provided "out of the box" clustering, fail-over, and a durable message store to play back history. There are some projects that may serve as good starting points, but not exactly what I am looking for.

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• Debugging delayed write failures to External HDD

  - by iceman

  Does the Window driver kit provide any debug tools to know delayed write failures on a 500 gb Seagate external USB 2.0 powered HDD?

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• Delayed startup of network icon (wi-fi)

  - by Michael Dy

  When my Windows 7 Starter netbook boots up and after everything is loaded, it takes about five minutes before the network icon near the clock becomes functional. When there's an available wi-fi signal (which automatically connects to my netbook as preconfigured) after the boot, my netbook seamlessly connects to it even if the network icon cannot be clicked or accessed. (The icon is shown to be loading for about five minutes.) During this time, when I go to Network and Sharing Center, it takes the same time to load. So even while the icon and the Center cannot be accessed, I can surf the Internet. When my netbook was still new, it didn't have this issue. How do I fix this?

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• Instant connection to wireless network but delayed internet access on Mediacom with Windows 7

  - by David

  I have Mediacom cable internet and their provided modem/wireless router a Cisco DPC3825. Each of the laptops experiencing the trouble have Windows 7 64-bit. When connecting to the wireless network each computer will take a second or two to connect and then toggle from "no internet access" to "internet access" however, no websites are accessible for about five minutes after connecting. After that, there aren't any problems. It happens on all 3 of the laptops I have available and none of them have problems on any other network. It seems like my phone doesn't have the delay issue when it connects. I've power cycled the modem/router along with a DNS flush. I have some of the DNS servers manually set to Google DNS addresses and one just default. I've contacted and had Mediacom support try all its tricks. They changed the SSID and password along with resetting the thing remotely a handful of times. It was installed just this month and seemed to pass the tech's checks upon installation. Nothing in the settings has been changed, but it's been exhibiting this problem from the get go. This guy seems to be having the same problem, but no solution was posted. http://www.dslreports.com/forum/r27372861-IA-Connection-to-Mediacom-wireless-Modem-no-internet- Help greatly appreciated.

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• Networking Problem MrxSmb event 50 "Delayed Write Failed" errors occurring all of the sudden

  - by Johnny Musso

  JUST THIS MONTH, we have started getting reports from a number of very stable clients that MrxSmb event id 50 errors keep appearing in their system event logs. Otherwise, they do not appear to have any networking problems except that there is a critical legacy application which seems to either be generating the MrxSmb errors or having errors occur because of them. The legacy application is comprised of 16 bit and 32 bit code and has not been changed or recompiled in many years. It has always been stable on Windows XP systems. The customers that have the problem usually have a small (5 clients or less) peer to peer network with all Windows XP systems. All service packs are loaded on the XP machines. Note: The only thing that seems to correct the problem is disabling opportunistic locking. I don't like this solution because it seems to slow down the network and sometimes causes record locking issues between users (on some networks). Also, this seems to have just started happening - as if a Windows update for XP has caused it? However, I have removed recent updates and it did not correct the issue. Thanks in advance for any help you can provide.

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• Internet Connection Sharing on OSX causes delayed web requests

  - by Vanthel

  I have an iMac connected to my router via WiFi, and a PC connected by ethernet to the iMac. The iMac is sharing its connection. I've never had a problem with this in the past (pre Lion anyway) but now all web page requests take an eon to resolve on the iMac (they are instant on the PC). It suggests to me the iMac is attempting to resolve it through the PC first every time? I've tried reordering the connections in the network settings but that made no difference.

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• Windows 7 delayed file delete

  - by GregoryM

  I'm stuck with a pretty rare problem that happens on Windows 7 OS only. Every time I'm deleting the file with *.exe extension through explorer, the file doesn't get deleted immediately. I'm forced to wait for around one-two minutes before the system will delete the file. The main problem is that I cannot develop in such situation, because every time I build my solution, the old executable gets 'deleted', but is still there. So the new one cannot be created by Visual Studio. This problem breaks the Steam update progress and a few other installers functionality too. Fresh installed Win7 doesn't have this kind of trouble, so I guess this must be some bad registry entries or some services. Browsing the internet for solutions I found only this: http://www.sevenforums.com/software/72091-several-minute-delay-when-deleting-any-exe-file.html. But the solution the author found is not working (change the userName :)). Is there any ideas how to find what causes this to happen? BTW: when I place the file into Trash bin, no delay occurs. When I delete file with Total Commander - no delay too. Tech details: Windows 7 x64 Ultimate.

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• Windows 7 delayed file delete

  - by GregoryM

  I'm stuck with a pretty rare problem that happens on Windows 7 OS only. Every time I'm deleting the file with *.exe extension through explorer, the file doesn't get deleted immediately. I'm forced to wait for around one-two minutes before the system will delete the file. The main problem is that I cannot develop in such situation, because every time I build my solution, the old executable gets 'deleted', but is still there. So the new one cannot be created by Visual Studio. This problem breaks the Steam update progress and a few other installers functionality too. Fresh installed Win7 doesn't have this kind of trouble, so I guess this must be some bad registry entries or some services. Browsing the internet for solutions I found only this: http://www.sevenforums.com/software/72091-several-minute-delay-when-deleting-any-exe-file.html. But the solution the author found is not working (change the userName :)). Is there any ideas how to find what causes this to happen? BTW: when I place the file into Trash bin, no delay occurs. When I delete file with Total Commander - no delay too. Tech details: Windows 7 x64 Ultimate. UPD: maybe some shadow copying or system restore services (though I have the system restore turned off) block the files? Can't even guess...

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• Previous Versions delayed with SBS 2008 / Windows 7

  - by indeed005

  The SBS 2008 at this site has Previous Versions enabled on a mapped drive. The snapshots happen 3 times a day. I doubt they take very long; the diff size is only a few GB. The problem is that the users on Windows 7 cannot see their previous versions until a few hours later. Is there some indexing that has to happen before the Previous Versions are visible to the client machines? Edit: In the application log, 3 minutes after every scheduled backup, there is an event for VSS (EventID 8224) saying "The VSS service is shutting down due to idle timeout" Apparently this means it has finished successfully, even though modified files still do not show another version.

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• Flash media server delayed streaming

  - by yn2

  I have a RED5 server I'm using to pass a live streaming between users' cameras. What I need now is a way to create a delayed broadcast of the camera (intended delay) so that "super users" will be able to see it immediately and others will get it 10-15 seconds later. If FMS is better for that, I will be happy to know why and how too. Any help will be appreciated.

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• Neko and haxe.Timer.delayed()

  - by vava

  As every haXe developer knows, you could use haxe.Timer.delayed() to delay function call for some time. But this function doesn't exist for neko at all. Is there a way to achieve the same results?

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• Delayed computation as DAG in .NET

  - by Tristan

  I'm playing around with declarative / delayed computation, where expressions are built up into a directed acyclic graph. Microsoft's GPU Accelerator does something similar. Are there any libraries available for .Net languages that makes it easier to build a representation of the computation?

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• variable in variable in batch and delayed expansion

  - by rezna

  Hi, I'm trying to use variable in variable in conjunction with delayed expansion but still no luck. SETLOCAL EnableDelayedExpansion SET ERROR_COMMAND=exit /B ^!ERRORLEVEL^! This is my last try. I want to setup an ERROR_COMMAND to be called when one of the steps in batch file crashes. The command is supposed to be: IF ERRORLEVEL 1 !ERROR_COMMAND! or IF ERRORLEVEL 1 %ERROR_COMMAND% The thing is, I'm not able to find out, how to SET properly the ERROR_COMMAND variable, so that ERRORLEVEL is not evaluated at the time of assignment, but at the time of evaluating the variable Of course I can copy&paste the code all over the batch file, but using the variable just seems a bit prettier... Anyone? Thanks, Milan

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• Delayed evaluation in Clojure

  - by StackedCrooked

  I'm having some trouble understanding how the delay macro works in Clojure. It doesn't seem to do what expect it to do (that is: delaying evaluation). As you can see in this code sample: ; returns the current time (defn get-timestamp [] (.getTime (java.util.Date.))) ; var should contain the current timestamp after calling "force" (def current-time (delay (get-timestamp))) However, calling current-time in the REPL appears to immediately evaluate the expression, even without having used the force macro: user=> current-time #<Delay@19b5217: 1276376485859> user=> (force current-time) 1276376485859 Why was the evaluation of get-timestamp not delayed until the first force call?

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• After interruption, delayed audio route change notifications when recording

  - by Frank Shearar

  My iPhone application requires that I know when a user has/has not plugged in her headphones. That's easy. AudioSessionAddPropertyListener with a callback listening to kAudioSessionProperty_AudioRouteChange. I write logs with NSLog as things happen. User plugs the headphones in? Get a notification, and a line in the gdb console. User unplugs the headphones? Ditto. At the same time I'm sensing the noise level of the environment by starting a recording audio queue. This, too, works great: I can get the mic noise level and listen for audio route changes just fine. What I find is that after an interruption, and I've reactivated the audio session and restored the audio category to kAudioSessionCategory_RecordAudio, the audio route notifications go a bit haywire. When I plug in the headphones, I see no notification. When I unplug the headphones I see BOTH the "plugged in" notification AND the "unplugged" notification, in rapid succession. It's like the "plugged in" notification's delayed and, when the "unplugged" notification arrives, the queue of pending notifications is flushed. What am I doing wrong? How do I correctly restore the audio session to get timeous notifications? EDIT: iPhone OS 3.1.2, running on an iPhone 3G. I'm running a program compiled with the 3.0 SDK (from within XCode 3.1.2).

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• cancelPreviousPerformRequestWithTarget is not canceling my previously delayed thread started with pe

  - by jmurphy

  Hello, I've launched a delayed thread using performSelector but the user still has the ability to hit the back button on the current view causing dealloc to be called. When this happens my thread still seems to be called which causes my app to crash because the properties that thread is trying to write to have been released. To solve this I am trying to call cancelPreviousPerformRequestsWithTarget to cancel the previous request but it doesn't seem to be working. Below are some code snippets. - (void) viewDidLoad { [self performSelector:@selector(myStopUpdatingLocation) withObject:nil afterDelay:6]; } (void)viewWillDisappear:(BOOL)animated { [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(myStopUpdatingLocation) object:nil]; } Am I doing something incorrect here? The method myStopUpdatingLocation is defined in the same class that I'm calling the perform requests. A little more background. The function that I'm trying to implement is to find a users location, search google for some locations around that location and display several annotations on the map. On viewDidLoad I start updating the location with CLLocationManager. I've build in a timeout after 6 seconds if I don't get my desired accuracy within the timeout and I'm using a performSelector to do this. What can happen is the user clicks the back button in the view and this thread will still execute even though all my properties have been released causing a crash. Thanks in advance! James

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• delayed_job :run_at is not working. all jobs set to run at current time

  - by jtwg

  I have installed the collectiveidea fork for delayed_job at git://github.com/collectiveidea/delayed_job.git but cannot get it to accept :run_at from my gemfile gem 'rails', '3.2.2' gem 'delayed_job_active_record' when I try it in the console 1.9.2-p318 :005 > Time.now => 2012-03-24 10:20:34 -0700 1.9.2-p318 :006 > User.delay.new :run_at => 5.days.from_now SQL (0.1ms) BEGIN SQL (1.6ms) INSERT INTO `delayed_jobs` (`attempts`, `created_at`, `failed_at`, `handler`, `last_error`, `locked_at`, `locked_by`, `priority`, `run_at`, `updated_at`) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?) [["attempts", 0], ["created_at", Sat, 24 Mar 2012 17:20:36 UTC +00:00], ["failed_at", nil], ["handler", "--- !ruby/object:Delayed::PerformableMethod\nobject: !ruby/class 'User'\nmethod_name: :new\nargs:\n- :run_at: 2012-03-29 17:20:36.876374000Z\n"], ["last_error", nil], ["locked_at", nil], ["locked_by", nil], ["priority", 0], ["run_at", Sat, 24 Mar 2012 17:20:36 UTC +00:00], ["updated_at", Sat, 24 Mar 2012 17:20:36 UTC +00:00]] (2.7ms) COMMIT => #<Delayed::Backend::ActiveRecord::Job id: 17, priority: 0, attempts: 0, handler: "--- !ruby/object:Delayed::PerformableMethod\nobject:...", last_error: nil, run_at: "2012-03-24 17:20:36", locked_at: nil, failed_at: nil, locked_by: nil, created_at: "2012-03-24 17:20:36", updated_at: "2012-03-24 17:20:36"> I see there is some UTC offset in the runtime, but based on Time.now, I can tell run_at is not going forward by 5 days. "run_at", Sat, 24 Mar 2012 17:20:36 UTC +00:00 Any ideas?

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• How do I set a service startup type to be 'Automatic (delayed)' using GPO?

  - by growse

  A Windows service has 4 different startup types that can be configured: Automatic, Automatic (delayed), Manual and Disabled. I have a service running on a combination of Windows 7 and Server 2008 R2 Desktops that I need to set as 'Automatic (delayed)' using a GPO setting, but from what I can see in the GPO editor, the delayed option is missing: Have I missed something obvious, or is this a rather basic omission from Microsoft?

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• SQL SERVER – Introduction to SQL Server 2014 In-Memory OLTP

  - by Pinal Dave

  In SQL Server 2014 Microsoft has introduced a new database engine component called In-Memory OLTP aka project “Hekaton” which is fully integrated into the SQL Server Database Engine. It is optimized for OLTP workloads accessing memory resident data. In-memory OLTP helps us create memory optimized tables which in turn offer significant performance improvement for our typical OLTP workload. The main objective of memory optimized table is to ensure that highly transactional tables could live in memory and remain in memory forever without even losing out a single record. The most significant part is that it still supports majority of our Transact-SQL statement. Transact-SQL stored procedures can be compiled to machine code for further performance improvements on memory-optimized tables. This engine is designed to ensure higher concurrency and minimal blocking. In-Memory OLTP alleviates the issue of locking, using a new type of multi-version optimistic concurrency control. It also substantially reduces waiting for log writes by generating far less log data and needing fewer log writes. Points to remember Memory-optimized tables refer to tables using the new data structures and key words added as part of In-Memory OLTP. Disk-based tables refer to your normal tables which we used to create in SQL Server since its inception. These tables use a fixed size 8 KB pages that need to be read from and written to disk as a unit. Natively compiled stored procedures refer to an object Type which is new and is supported by in-memory OLTP engine which convert it into machine code, which can further improve the data access performance for memory –optimized tables. Natively compiled stored procedures can only reference memory-optimized tables, they can’t be used to reference any disk –based table. Interpreted Transact-SQL stored procedures, which is what SQL Server has always used. Cross-container transactions refer to transactions that reference both memory-optimized tables and disk-based tables. Interop refers to interpreted Transact-SQL that references memory-optimized tables. Using In-Memory OLTP In-Memory OLTP engine has been available as part of SQL Server 2014 since June 2013 CTPs. Installation of In-Memory OLTP is part of the SQL Server setup application. The In-Memory OLTP components can only be installed with a 64-bit edition of SQL Server 2014 hence they are not available with 32-bit editions. Creating Databases Any database that will store memory-optimized tables must have a MEMORY_OPTIMIZED_DATA filegroup. This filegroup is specifically designed to store the checkpoint files needed by SQL Server to recover the memory-optimized tables, and although the syntax for creating the filegroup is almost the same as for creating a regular filestream filegroup, it must also specify the option CONTAINS MEMORY_OPTIMIZED_DATA. Here is an example of a CREATE DATABASE statement for a database that can support memory-optimized tables: CREATE DATABASE InMemoryDB ON PRIMARY(NAME = [InMemoryDB_data], FILENAME = 'D:\data\InMemoryDB_data.mdf', size=500MB), FILEGROUP [SampleDB_mod_fg] CONTAINS MEMORY_OPTIMIZED_DATA (NAME = [InMemoryDB_mod_dir], FILENAME = 'S:\data\InMemoryDB_mod_dir'), (NAME = [InMemoryDB_mod_dir], FILENAME = 'R:\data\InMemoryDB_mod_dir') LOG ON (name = [SampleDB_log], Filename='L:\log\InMemoryDB_log.ldf', size=500MB) COLLATE Latin1_General_100_BIN2; Above example code creates files on three different drives (D:  S: and R:) for the data files and in memory storage so if you would like to run this code kindly change the drive and folder locations as per your convenience. Also notice that binary collation was specified as Windows (non-SQL). BIN2 collation is the only collation support at this point for any indexes on memory optimized tables. It is also possible to add a MEMORY_OPTIMIZED_DATA file group to an existing database, use the below command to achieve the same. ALTER DATABASE AdventureWorks2012 ADD FILEGROUP hekaton_mod CONTAINS MEMORY_OPTIMIZED_DATA; GO ALTER DATABASE AdventureWorks2012 ADD FILE (NAME='hekaton_mod', FILENAME='S:\data\hekaton_mod') TO FILEGROUP hekaton_mod; GO Creating Tables There is no major syntactical difference between creating a disk based table or a memory –optimized table but yes there are a few restrictions and a few new essential extensions. Essentially any memory-optimized table should use the MEMORY_OPTIMIZED = ON clause as shown in the Create Table query example. DURABILITY clause (SCHEMA_AND_DATA or SCHEMA_ONLY) Memory-optimized table should always be defined with a DURABILITY value which can be either SCHEMA_AND_DATA or  SCHEMA_ONLY the former being the default. A memory-optimized table defined with DURABILITY=SCHEMA_ONLY will not persist the data to disk which means the data durability is compromised whereas DURABILITY= SCHEMA_AND_DATA ensures that data is also persisted along with the schema. Indexing Memory Optimized Table A memory-optimized table must always have an index for all tables created with DURABILITY= SCHEMA_AND_DATA and this can be achieved by declaring a PRIMARY KEY Constraint at the time of creating a table. The following example shows a PRIMARY KEY index created as a HASH index, for which a bucket count must also be specified. CREATE TABLE Mem_Table ( [Name] VARCHAR(32) NOT NULL PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT = 100000), [City] VARCHAR(32) NULL, [State_Province] VARCHAR(32) NULL, [LastModified] DATETIME NOT NULL, ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA); Now as you can see in the above query example we have used the clause MEMORY_OPTIMIZED = ON to make sure that it is considered as a memory optimized table and not just a normal table and also used the DURABILITY Clause= SCHEMA_AND_DATA which means it will persist data along with metadata and also you can notice this table has a PRIMARY KEY mentioned upfront which is also a mandatory clause for memory-optimized tables. We will talk more about HASH Indexes and BUCKET_COUNT in later articles on this topic which will be focusing more on Row and Index storage on Memory-Optimized tables. So stay tuned for that as well. Now as we covered the basics of Memory Optimized tables and understood the key things to remember while using memory optimized tables, let’s explore more using examples to understand the Performance gains using memory-optimized tables. I will be using the database which i created earlier in this article i.e. InMemoryDB in the below Demo Exercise. USE InMemoryDB GO -- Creating a disk based table CREATE TABLE dbo.Disktable ( Id INT IDENTITY, Name CHAR(40) ) GO CREATE NONCLUSTERED INDEX IX_ID ON dbo.Disktable (Id) GO -- Creating a memory optimized table with similar structure and DURABILITY = SCHEMA_AND_DATA CREATE TABLE dbo.Memorytable_durable ( Id INT NOT NULL PRIMARY KEY NONCLUSTERED Hash WITH (bucket_count =1000000), Name CHAR(40) ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA) GO -- Creating an another memory optimized table with similar structure but DURABILITY = SCHEMA_Only CREATE TABLE dbo.Memorytable_nondurable ( Id INT NOT NULL PRIMARY KEY NONCLUSTERED Hash WITH (bucket_count =1000000), Name CHAR(40) ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_only) GO -- Now insert 100000 records in dbo.Disktable and observe the Time Taken DECLARE @i_t bigint SET @i_t =1 WHILE @i_t<= 100000 BEGIN INSERT INTO dbo.Disktable(Name) VALUES('sachin' + CONVERT(VARCHAR,@i_t)) SET @i_t+=1 END -- Do the same inserts for Memory table dbo.Memorytable_durable and observe the Time Taken DECLARE @i_t bigint SET @i_t =1 WHILE @i_t<= 100000 BEGIN INSERT INTO dbo.Memorytable_durable VALUES(@i_t, 'sachin' + CONVERT(VARCHAR,@i_t)) SET @i_t+=1 END -- Now finally do the same inserts for Memory table dbo.Memorytable_nondurable and observe the Time Taken DECLARE @i_t bigint SET @i_t =1 WHILE @i_t<= 100000 BEGIN INSERT INTO dbo.Memorytable_nondurable VALUES(@i_t, 'sachin' + CONVERT(VARCHAR,@i_t)) SET @i_t+=1 END The above 3 Inserts took 1.20 minutes, 54 secs, and 2 secs respectively to insert 100000 records on my machine with 8 Gb RAM. This proves the point that memory-optimized tables can definitely help businesses achieve better performance for their highly transactional business table and memory- optimized tables with Durability SCHEMA_ONLY is even faster as it does not bother persisting its data to disk which makes it supremely fast. Koenig Solutions is one of the few organizations which offer IT training on SQL Server 2014 and all its updates. Now, I leave the decision on using memory_Optimized tables on you, I hope you like this article and it helped you understand  the fundamentals of IN-Memory OLTP . Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: Koenig

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