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  • Problems setting NTP sever with w32tm for a DC that is a Hyper-V guest

    - by R.Tonheim
    Hello ! I have tried to sett my DC to get its time from several NTP severs. I follow this answer (http://serverfault.com/questions/24298/w32time-sync-problems-for-hyper-v-guests-w32time-event-ids-38-24-29-35/24299#24299) to do it. First I disable Time Synchronization in the Hyper-V Integration Services for each guest. Then restart the Windows Time serviceon the guest. I had before this used this command: w32tm /config /manualpeerlist:"ntp.uio.no;timekeeper. uio.no;nissen.uio.no;0.no.pool.ntp.org;1.no.pool.ntp.org;2.no.pool.ntp.org" /syn cfromflags:manual /reliable:yes /update And the cmd sad: The command completed successfully. But the time was still 10 min wrong... I run w32tm again after restarted the DC without it having any effect. The w32tm /query /status still say: "Source: Local CMOS Clock" FROM MY CMD: Microsoft Windows [Version 6.0.6002] Copyright (c) 2006 Microsoft Corporation. All rights reserved. C:\Users\Administrator.MHGw32tm /query /status Leap Indicator: 0(no warning) Stratum: 1 (primary reference - syncd by radio clock) Precision: -6 (15.625ms per tick) Root Delay: 0.0000000s Root Dispersion: 10.0000000s ReferenceId: 0x4C4F434C (source name: "LOCL") Last Successful Sync Time: 05.09.2009 20:06:21 Source: Local CMOS Clock Poll Interval: 6 (64s) C:\Users\Administrator.MHGw32tm /config /manualpeerlist:"ntp.uio.no;timekeeper. uio.no;nissen.uio.no;0.no.pool.ntp.org;1.no.pool.ntp.org;2.no.pool.ntp.org" /syn cfromflags:manual /reliable:yes /update The command completed successfully. C:\Users\Administrator.MHGw32tm /query /status Leap Indicator: 0(no warning) Stratum: 1 (primary reference - syncd by radio clock) Precision: -6 (15.625ms per tick) Root Delay: 0.0000000s Root Dispersion: 10.0000000s ReferenceId: 0x4C4F434C (source name: "LOCL") Last Successful Sync Time: 05.09.2009 20:06:21 Source: Local CMOS Clock Poll Interval: 6 (64s) C:\Users\Administrator.MHG

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  • Sharing large (multi-Gb) files with clients

    - by Tim Long
    I wasn't sure if this was the best place for this question, but I think it is squarely in the realm of the IT admin so that's the reason I put it here. We need to share large files (several Gigabytes) with external clients. We need a simple way of reliably and automatically publishing these files so that clients can then download them. Our organization has Windows desktops and a Windows SBS 2011 server. Sharing from our server is probably suboptimal from the client's perspective, because of the low upstream bandwidth of typical ADSL (around 1 Mbps) - it would take all day (9 hours for a 4Gb file) for the client to download the file. Uploading to a 3rd party sever is good for the client but painful for us, because we then have to deal with a multi-hour upload. Uploading to a third-part server would be less problematic if it could be made reliable and automatic, e.g. something like a Groove/SharePoint Workspace, simply drop the file in and wait for it to synchronize - but Groove has a 2Gb limit which is not big enough. So ideally I'd like a service with the following attributes: Must work for files of at least 5Gb, preferably 10Gb Once the transfer is started, it must be reliable (i.e. not sensitive to disconnections and service outages) and completely automatic Ideally, the sender would get a notification when the transfer completes. Has to work with Windows based systems. Any suggestions?

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  • MMC crashes on Windows Server 2008 x64 - Exchange console, event viewer

    - by David M Williams
    Help! I don't know what happened; this server has been very reliable but suddenly began having problems with a particular .NET 2.0 web site simply hanging - it wouldn't load at all. However, another ASP.NET site was still fine. Reinstalling the site didn't fix it, nor did deleting and re-creating the application within IIS. Trying the event viewer was met with a horrifying "Microsoft Management Console has stopped working". Some Googling led me to believe the .NET framework was the problem. I found a tool called the .NET cleanup tool - http://blogs.msdn.com/astebner/pages/8904493.aspx - which cleaned out .NET entirely. I reinstalled .NET 1.1 and 3.5 (which installed 2.0 and 3.0 as well). Using the .NET verification tool - http://blogs.msdn.com/astebner/pages/8999004.aspx - I believe these have all installed ok. However, my server is in worse shape now. The Exchange 2010 Management Console crashes with an MMC error and now my other (previously reliable) .NET web app now hangs on loading too. I thought I should use Computer Management to remove and re-add the application and web server roles but sure enough, MMC crashes. If anyone can help I will be extremely grateful. Thank you !

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  • Which internet scenario would be better?

    - by JL
    I currently have an 8mbps (down) / 512kbps (up) telephone ADSL solution. I must say the reliability is excellent, and up until now its been the fastest connection I could get because I don't live in a cable zone. The real speed of my connection is around 7mbps, but sometimes I manage to get the full 8mbps. I use my connection for work, so it needs to be at least 99% reliable. Recently I was told by a guy who lives up the road that he has a wireless connection with an external antenna and his speeds are 20mbps / 512kbps - he's also paying about 1/2 of what I pay for my wired telephone connection. My question is, is wireless internet good enough for a power user who uses his connection for work 8 hours a day, including VPNing into servers remotely. Besides this I also enjoy playing the odd network game, not a WoW freak, but sometimes I do pick up the odd MMORPG and at times do indulge in some semi heavy gaming sprees. Will this wireless latency drive me crazy and seem slow in comparison? Will it be reliable enough, I also live in an area that snows heavily in winter. I guess its a question of - should I go wireless or not. I've only had 1 wireless connection before and that was years ago using iBurst technology and I remember it was terrible for VPN, but I guess the technology might have been improved since then? What do you guys think?

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  • How to monitor changes in the frequency of network latency spikes over time?

    - by dequis
    I'm currently trying to troubleshoot an issue with my network in which I get latency spikes up to 200 seconds (normally around 50 secs) in an apparently random way at apparently random moments of the day. While trying to find what part of my messy network needs to be blamed (outside of the scope of this question - discussed a bit on chat), I realized I have no reliable way to confirm that a change actually improved anything. So far, the main way in which i notice this is that irssi shows [Lag: 15 (??)] in the statusbar, increasing every 5 seconds, and all other connections seem to be affected too. Since this depends on my observations, it's not a very reliable method to know how often it really happens. Note that just sending ICMP pings is probably not enough, but that's just my guess. It might be a "bufferbloat" issue, it might be packet loss, it might only apply to persistent connections. I suspect this because a few months ago, when the issue started, I had a "ping" command running in background and it didn't show anything weird at all during the latency spikes. This seems to have changed now (pings don't go through), but still, I'd prefer something more robust.

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  • Changes to grub in ubuntu 10

    - by jdege
    I've been running CentOS 5 for some years. I've decided to upgrade to Ubuntu, and with 10.04 just out, this seemed like a good time. I'm a tad paranoid, so I started off with a new set of drives - one to install on, one to backup to, and one as a spare. I removed my existing CentOS 5 drives, and did an install, and had no problems. I installed the server version, and used the default full-disk LVM installation. Next, I copies my backup scripts over, edited them to work with the new configuration, and did a test backup. That worked fine, as well. Then comes the real test, could I do an install of the backup onto the spare drive? (I won't put anything of importance on a system that doesn't have a reliable backup, and if I've never done a restore, it's not reliable.) I booted from a System Rescue CD (ver 1.5.3), with the spare drive as /dev/sda, and the backup drive as /dev/sdb. I had no trouble in partitioning, configuring LVM, formatting, making swap, or restoring the file systems. But when I got to restoring grub to the MBR, I ran into problems. My restore instructions from CentOS 5 said run grub, then enter two commands: root (hd0,0) setup (hd0) The first command exits with an error: "Checking if /boot/grub/stage1 exists ... no" I did some googling around, and found that the Grub2 included in recent Ubuntus is very different than the Grub 0.97 included in CentOS 5. One site suggested I use: grub-install --root-dir=/mnt/restore /dev/sda That appeared to work, but when I booted from the drive, I ended up at a grub prompt. Any ideas as to what I need to do? It seems like a simple problem, but my attempts at searching out answers on the web are being swamped by references to the old version of Grub. Help would be appreciated.

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  • how to define service runlevel order position?

    - by DmitrySemenov
    I setup bind-dlz and need mysql start prior NAMED when system starts here is what I have [root@semenov]# ./test.sh mysql 0:off 1:off 2:on 3:on 4:on 5:on 6:off named 0:off 1:off 2:off 3:on 4:on 5:on 6:off lrwxrwxrwx. 1 root root 15 Apr 15 18:57 /etc/rc3.d/S93mysql -> ../init.d/mysql lrwxrwxrwx. 1 root root 15 Apr 15 18:57 /etc/rc3.d/S90named -> ../init.d/named here is what I have in mysql init script # Comments to support chkconfig on RedHat Linux # chkconfig: 2345 84 16 # description: A very fast and reliable SQL database engine. # Comments to support LSB init script conventions ### BEGIN INIT INFO # Provides: mysql # Required-Start: $local_fs $network $remote_fs # Should-Start: ypbind nscd ldap ntpd xntpd # Required-Stop: $local_fs $network $remote_fs # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: start and stop MySQL # Description: MySQL is a very fast and reliable SQL database engine. ### END INIT INFO so when I remove named from chkconfig and have there just mysql, it starts with order number 84: /etc/rc3.d/S84mysql - ../init.d/mysql but when I add named inside chkconfig it's order changes to 93: /etc/rc3.d/S93mysql - ../init.d/mysql as a result mysql will be starting after named and named will fail (no sql available) any ideas what I'm doing wrong? here is what I have in named init script # chkconfig: 345 90 16 # description: named (BIND) is a Domain Name Server (DNS) \ # that is used to resolve host names to IP addresses. # probe: true ### BEGIN INIT INFO # Provides: $named # Required-Start: $local_fs $network $syslog # Required-Stop: $local_fs $network $syslog # Default-Start:2 3 4 # Default-Stop: 0 1 2 3 4 5 6 # Short-Description: start|stop|status|restart|try-restart|reload|force-reload DNS server # Description: control ISC BIND implementation of DNS server ### END INIT INFO thanks, Dmitry

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  • Feasibility of Windows Server 2008 DFS replication over WAN link

    - by CesarGon
    We have just set up a WAN link that connects two buildings in our organisation. The link is provided by a 100-Mbps point to point line. We have a Windows Server 2008 R2 domain controller on each side of the link. Now we are planning to set up DFS for file services across the organisation. The estimated data volume is over 2 TB, and will grow at approximately 20% annually. My idea is to set up a file server in each building and install DFS so that all the contents stay replicated over the 100-Mbps link. I hope that this will ensure that any user will be directed to the closest (and fastest) server when requesting a file from the DFS folders. My concern is whether a 100-Mbps WAN link is good enough to guarantee DFS replication. I've no experience with DFS, so any solid advice is welcome. The line is reliable (i.e. it doesn't crash often) and our data transfer tests show that a 5 MB/sec transfer rate is easily achieved. This is approximately 40% of the nominal bandwidth. I am also concerned about the latency. I mean, how long will users need to wait to see one change on one side of the link after the change has been made on the other side. My questions are: Is this link between networks a reliable infrastructure on which to set up DFS replication? What latency times would be typical (seconds, minutes, hours, days)? Would you recommend that we go for DFS in this scenario, or is there a better alternative? Many thanks.

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  • Apache, Tomcat and mod_jk for load balancing

    - by pHk
    Hi guys. I've set-up a basic Apache (2.2.x) and Tomcat (6.0.x) set-up using mod_jk for load balancing using the worker.properties file. Preliminary testing seems to show that this works relatively well, and it was quite easy to set-up. However; the fact that it was so easy to set-up has got me a little worried. We're dealing with 100 - 300 concurrent users using the same web application (deployed on 2 or 3 Tomcat instances). I have done a little Googling and looking around on here and there seems to be more than 1 way to accomplish this (one example on here used a balancer:// style URL, which I've never seen before in an Apache config). For example, one question I ask myself is how reliable the load detection on mod_jk really is (Busyness, Session, Request, etc). In your experience, does this set-up prove to be reliable in real world scenarios? Any pointers on improvements, pit falls or interesting literature/articles? I've worked with Apache before, but am in no way an expert. Thanks in advance.

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  • Why does my simple Raid 1 backup storage perform really slow sometimes?

    - by randomguy
    I bought 2x Samsung F3 EcoGreen 2TB hard disks to make a backup storage. I put them in Raid 1 (mirror) mode. Made a single partition and formatted it to NTFS, running Windows 7. For some reason, accessing the drive's contents (simply by navigating folders) is sometimes really slow. Like opening D:/photos/ can sometimes take several seconds before it starts showing any of the folder's contents. Same applies for other folders. What could be causing this and what could I do to improve the performance? I remember that there was an option somewhere inside Windows to choose fast access but less reliable persistence operations (read/write). It was a tick inside some dialog. At the time, it felt like a good idea to take the tick away from the option and get more reliable persistence but slower access, but now I'm regretting. I'm unable to find this dialog.. I've looked hard. I don't know, if it would make any difference. Oh, and I've ran scan disk and defrag on the drive. No errors and speed isn't improved.

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  • What is the potential for a FUSE mount to destabilize a Linux server?

    - by 200_success
    I'm a sysadmin for a multi-user server, where students in our department have shell accounts. One of our users has requested that we install sshfs on it. I'm debating whether it would be wise to install sshfs as suggested. My main concern is whether a FUSE mount could make our server less reliable. In my experience, bad things can happen to servers when an NFS server suddenly becomes unavailable — the load average shoots up, and you might not be able to unmount it cleanly, to the point where a hard reboot might be necessary. If a FUSE-mounted server suddenly disappears, how hard might it be to clean up the mess? Are there any other likely catastrophes or gotchas I should consider? At least with NFS, only root can mount, and we can choose to mount NFS servers that we consider to be reasonably reliable. Let's assume that our users have no hostile intentions, but might do stupid things accidentally. Also, I'm not really worried about the contents of the filesystems they might mount, since our users already have shell access and can copy anything they want to their home directory.

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  • Building services with .Net Part 1

    - by Allan Rwakatungu
    On the 26th of May 2010 , I made a presentation to the .NET user group meeting (thanks to Malisa Ncube for organizing this event every month … ). If you missed my presentation , we talked about why we should all be building services … better still using the .NET framework. This blog post is an introduction to services , why you would want to build services and how you can build services using the .NET framework. What is a service? OASIS defines service as "a mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface and is exercised consistent with constraints and policies as specified by the service description." [1]. If the above definition sounds to academic , you can also define a service as loosely coupled units of functionality that have no calls to each other embedded in the. Instead of services embedding calls to each other in their service code they use defined protocols that describe how services pass and parse messages. This is a good way to think about services if you’re from an objected oriented background. While in object oriented programming functions make calls to each other, in service oriented programming, functions pass messages between each other. Why would you want to use services? 1. If your enterprise architecture looks like this   Services are the building blocks for SOA . With SOA you can move away from the sphaggetti infrastructure that is common in most enterprises. The complexity or lack of visibility of the integration points in your enterprises makes it difficult and costly to implement new initiatives and changes into the business - and even impossible in some cases - as it is not possible to identify the impact a change in one system might have to other systems. With services you can move to an architecture like this Your building blocks from Spaghetti infrastructure to something that is more well-defined and manageable to achieve cost efficiency and not least business agility - enabling you to react to changes in the market with speed and achieve operational efficiency and control are services. 2. If you want to become the Gates or Zuckerburger. Have you heard about Web 2.0 ? Mashups? Software as a service (SAAS) ? Cloud computing ?   They all offer you the opportunity to have scalable but low cost business models and they built using services.  Some of my favorite companies that leverage services for their business models include  https://www.salesforce.com/ (cloud CRM) http://www. twitter.com (more people use twitter clients built by 3rd parties than their official clients) http://www.kayak.com/ (compares data from other travel sites to give information to users in one location) Services with the .NET framework      If you are a .NET developer and you want to develop services, Windows Communication Framework (WCF) is the tool for you. WCF is Microsoft’s unified programming model (service model) for building service oriented applications. ( Before .NET 3.0 you had several models for programming services in .NET including .NET remoting, Web services (ASMX), COM +, Microsoft Messaging queuing (MSMQ) etc, after .NET 3.0 the programming model was unified into one i.e. WCF ). Windows Communication Framework (WCF) provides you 1. An Software Development Kit (SDK) for creating SOA applications 2. A runtime for running services on the Windows platform Why should you use Windows Communication Foundation if you’re programming services?   1. It supports interoperable and open standards e.g. WS* protocols for programming SOAP services 2. It has a unified programming model. Whether you use TCP or Http or Pipes or transmitting using Messaging Queues, programmers need to learn just one way to program. Previously you had .NET remoting, MSMQ, Web services, COM+ and they were all done differently 3. Productive programming model You don’t have to worry about all the plumbing involved to write services. You have a rich declarative programming model to add stuff like logging, transactions, and reliable messages in-built in the Windows Communication Framework. Understanding services in WCF The basic principles of WCF are as easy as ABC A – Address This is where the service is located B- Binding This describes how you communicate with the service e.g. Use TCP, HTTP or both. How to exchange security information with the service etc. C – Contract This defines what the service can do. E.g. Pay water bill, Make a phone call A - Addresses In WCF, an address is a combination of transport, server name, port and path Example addresses may include http://localhost:8001 net.tcp://localhost:8002/MyService net.pipe://localhost/MyPipe net.msmq://localhost/private/MyService net.msmq://localhost/MyService B- Binding   There are numerous ways to communicate with services , different ways that a message can be formatted/sent/secured, that allows you to tailor your service for the compatibility/performance you require for your solution. Transport You can use HTTP TCP MSMQ , Named pipes, Your own custom transport etc Message You  can send a plain text binary, Message Transmission Optimization Mechanism (MTOM) message Communication security No security Transport security Message security Authenticating and authorizing callers etc Behaviour You service can support Transactions Be reliable Use queues Support ajax etc C - Contract You define what your service can do using Service contracts :- Define operations that your service can do, communications and behaviours Data contracts :- Define the messages that are passed from and into your service and how they are formatted Fault contracts :- Defines errors types in your service   As an example, suppose your service service shows money. You define your service contract using a interface [ServiceContract] public interface IShowMeTheMoney {   [OperationContract]    Money Show(); } You define the data contract by annotating a class it with the Data Contract attribute and fields you want to pass in the message as Data Members. (Note:- In the latest versions of WCF you dont have to use attributes if you passing all the objects properties in the message) [DataContract] public Money {   [DataMember]   public string Currency { get; set; }   [DataMember]   public Decimal Amount { get; set; }   public string Comment { get; set; } } Features of Windows Communication Foundation Windows Communication Foundation is not only simple but feature rich , offering you several options to tweak your service to fit your business requirements. Some of the features of WCF include 1. Workflow services You can combine WCF with Windows WorkFlow Foundation (WWF) to write workflow type services 2. Control how your data (messages) are transferred and serialized e.g. you can serialize your business objects as XML or binary 3. control over session management , instance creation and concurrency management without writing code if you like 4. Queues and reliable sessions. You can store messages from the sending client and later forward them to the receiving application. You can also guarantee that messages will arrive at their destincation. 5.Transactions:  You can have different services participate in a transaction operations that can be rolled back if needed 6. Security. WCF has rich features for authorization and authentication  as well as keep audit trails 7. Web programming model. WCF allows developers to expose services as non SOAP endpoints 8. Inbuilt features that you can use to write JSON and services that support AJAX applications And lots more In my next blog I will show you how you can use WCF features to write a real world business service.               Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 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-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • SQL SERVER – 2012 – All Download Links in Single Page – SQL Server 2012

    - by pinaldave
    SQL Server 2012 RTM is just announced and recently I wrote about all the SQL Server 2012 Certification on single page. As a feedback, I received suggestions to have a single page where everything about SQL Server 2012 is listed. I will keep this page updated as new updates are announced. Microsoft SQL Server 2012 Evaluation Microsoft SQL Server 2012 enables a cloud-ready information platform that will help organizations unlock breakthrough insights across the organization. Microsoft SQL Server 2012 Express Microsoft SQL Server 2012 Express is a powerful and reliable free data management system that delivers a rich and reliable data store for lightweight Web Sites and desktop applications. Microsoft SQL Server 2012 Feature Pack The Microsoft SQL Server 2012 Feature Pack is a collection of stand-alone packages which provide additional value for Microsoft SQL Server 2012. Microsoft SQL Server 2012 Report Builder Report Builder provides a productive report-authoring environment for IT professionals and power users. It supports the full capabilities of SQL Server 2012 Reporting Services. Microsoft SQL Server 2012 Master Data Services Add-in For Microsoft Excel The Master Data Services Add-in for Excel gives multiple users the ability to update master data in a familiar tool without compromising the data’s integrity in Master Data Services. Microsoft SQL Server 2012 Performance Dashboard Reports The SQL Server 2012 Performance Dashboard Reports are Reporting Services report files designed to be used with the Custom Reports feature of SQL Server Management Studio. Microsoft SQL Server 2012 PowerPivot for Microsoft Excel® 2010 Microsoft PowerPivot for Microsoft Excel 2010 provides ground-breaking technology; fast manipulation of large data sets, streamlined integration of data, and the ability to effortlessly share your analysis through Microsoft SharePoint. Microsoft SQL Server 2012 Reporting Services Add-in for Microsoft SharePoint Technologies 2010 The SQL Server 2012 Reporting Services Add-in for Microsoft SharePoint 2010 technologies allows you to integrate your reporting environment with the collaborative SharePoint 2010 experience. Microsoft SQL Server 2012 Semantic Language Statistics The Semantic Language Statistics Database is a required component for the Statistical Semantic Search feature in Microsoft SQL Server 2012 Semantic Language Statistics. Microsoft ®SQL Server 2012 FileStream Driver – Windows Logo Certification Catalog file for Microsoft SQL Server 2012 FileStream Driver that is certified for WindowsServer 2008 R2. It meets Microsoft standards for compatibility and recommended practices with the Windows Server 2008 R2 operating systems. Microsoft SQL Server StreamInsight 2.0 Microsoft StreamInsight is Microsoft’s Complex Event Processing technology to help businesses create event-driven applications and derive better insights by correlating event streams from multiple sources with near-zero latency. Microsoft JDBC Driver 4.0 for SQL Server Download the Microsoft JDBC Driver 4.0 for SQL Server, a Type 4 JDBC driver that provides database connectivity through the standard JDBC application program interfaces (APIs) available in Java Platform, Enterprise Edition 5 and 6. Data Quality Services Performance Best Practices Guide This guide focuses on a set of best practices for optimizing performance of Data Quality Services (DQS). Microsoft Drivers 3.0 for SQL Server for PHP The Microsoft Drivers 3.0 for SQL Server for PHP provide connectivity to Microsoft SQLServer from PHP applications. Product Documentation for Microsoft SQL Server 2012 for firewall and proxy restricted environments The Microsoft SQL Server 2012 setup installs only the Help Viewer…install any documentation. All of the SQL Server documentation is available online. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Inappropriate Updates?

    - by Tony Davis
    A recent Simple-talk article by Kathi Kellenberger dissected the fastest SQL solution, submitted by Peter Larsson as part of Phil Factor's SQL Speed Phreak challenge, to the classic "running total" problem. In its analysis of the code, the article re-ignited a heated debate regarding the techniques that should, and should not, be deemed acceptable in your search for fast SQL code. Peter's code for running total calculation uses a variation of a somewhat contentious technique, sometimes referred to as a "quirky update": SET @Subscribers = Subscribers = @Subscribers + PeopleJoined - PeopleLeft This form of the UPDATE statement, @variable = column = expression, is documented and it allows you to set a variable to the value returned by the expression. Microsoft does not guarantee the order in which rows are updated in this technique because, in relational theory, a table doesn’t have a natural order to its rows and the UPDATE statement has no means of specifying the order. Traditionally, in cases where a specific order is requires, such as for running aggregate calculations, programmers who used the technique have relied on the fact that the UPDATE statement, without the WHERE clause, is executed in the order imposed by the clustered index, or in heap order, if there isn’t one. Peter wasn’t satisfied with this, and so used the ingenious device of assuring the order of the UPDATE by the use of an "ordered CTE", based on an underlying temporary staging table (a heap). However, in either case, the ordering is still not guaranteed and, in addition, would be broken under conditions of parallelism, or partitioning. Many argue, with validity, that this reliance on a given order where none can ever be guaranteed is an abuse of basic relational principles, and so is a bad practice; perhaps even irresponsible. More importantly, Microsoft doesn't wish to support the technique and offers no guarantee that it will always work. If you put it into production and it breaks in a later version, you can't file a bug. As such, many believe that the technique should never be tolerated in a production system, under any circumstances. Is this attitude justified? After all, both forms of the technique, using a clustered index to guarantee the order or using an ordered CTE, have been tested rigorously and are proven to be robust; although not guaranteed by Microsoft, the ordering is reliable, provided none of the conditions that are known to break it are violated. In Peter's particular case, the technique is being applied to a temporary table, where the developer has full control of the data ordering, and indexing, and knows that the table will never be subject to parallelism or partitioning. It might be argued that, in such circumstances, the technique is not really "quirky" at all and to ban it from your systems would server no real purpose other than to deprive yourself of a reliable technique that has uses that extend well beyond the running total calculations. Of course, it is doubly important that such a technique, including its unsupported status and the assumptions that underpin its success, is fully and clearly documented, preferably even when posting it online in a competition or forum post. Ultimately, however, this technique has been available to programmers throughout the time Sybase and SQL Server has existed, and so cannot be lightly cast aside, even if one sympathises with Microsoft for the awkwardness of maintaining an archaic way of doing updates. After all, a Table hint could easily be devised that, if specified in the WITH (<Table_Hint_Limited>) clause, could be used to request the database engine to do the update in the conventional order. Then perhaps everyone would be satisfied. Cheers, Tony.

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  • Tinyurl API Example - Am i doing it right :D

    - by Paul Weber
    Hi ... we use super-long Hashes for the Registration of new Users in our Application. The Problem is that these Hashes break in some Email Clients - making the Links unusable. I tried implementing the Tinyurl - API, with a simple Call, but i think it times out sometimes ... sometimes the mail does not reach the user. I updated the Code, but now the URL is never converted. Is Tinyurl really so slow or am i doing something wrong? (I mean hey, 5 Seconds is much in this Times) Can anybody recommend me a more reliable service? All my Fault, forgot a false in the fopen. But i will leave this sample of code here, because i often see this sample, wich i think does not work very reliable: return file_get_contents('http://tinyurl.com/api-create.php?url='.$u); This is the - i think fully working sample. I would like to hear about Improvements. static function gettinyurl( $url ) { $context = stream_context_create( array( 'http' => array( 'timeout' => 5 // 5 Seconds should be enough ) ) ); // get tiny url via api-create.php $fp = fopen( 'http://tinyurl.com/api-create.php?url='.$url, 'r', $context); // open (read) api-create.php with long url as get parameter if( $fp ) { // check if open was ok $tinyurl = fgets( $fp ); // read response if( $tinyurl && !empty($tinyurl) ) // check if response is ok $url = $tinyurl; // set response as url fclose( $fp ); // close connection } // return return $url; // return (tiny) url }

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  • Testing performance of queries in mysl

    - by Unreason
    I am trying to setup a script that would test performance of queries on a development mysql server. Here are more details: I have root access I am the only user accessing the server Mostly interested in InnoDB performance The queries I am optimizing are mostly search queries (SELECT ... LIKE '%xy%') What I want to do is to create reliable testing environment for measuring the speed of a single query, free from dependencies on other variables. Till now I have been using SQL_NO_CACHE, but sometimes the results of such tests also show caching behaviour - taking much longer to execute on the first run and taking less time on subsequent runs. If someone can explain this behaviour in full detail I might stick to using SQL_NO_CACHE; I do believe that it might be due to file system cache and/or caching of indexes used to execute the query, as this post explains. It is not clear to me when Buffer Pool and Key Buffer get invalidated or how they might interfere with testing. So, short of restarting mysql server, how would you recommend to setup an environment that would be reliable in determining if one query performs better then the other?

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  • JBoss Clustered Service that sends emails from txt file

    - by michael lucas
    I need a little push in the right direction. Here's my problem: I have to create an ultra-reliable service that sends email messages to clients whose addresses are stored in txt file on FTP server. Single txt file may contain unlimited number of entries. Most often the file contains about 300,000 entries. Service exposes interface with just two simple methods: TaskHandle sendEmails(String ftpFilePath); ProcessStatus checkProcessStatus(TaskHandle taskHandle); Method sendEmails() returns TaskHandle by which we can ask for ProcessStatus. For such a service to be reliable clustering is necessary. Processing single txt file might take a long time. Restarting one node in a cluster should have no impact on sending emails. We use JBoss AS 4.2.0 which comes with a nice HASingletonController that ensure one instance of service is running at given time. But once a fail-over happens, the second service should continue work from where the first one stopped. How can I share state between nodes in a cluster in such a way that leaves no possibility of sending some emails twice?

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  • Choosing between .NET Service Bus Queues vs Azure Queue Service

    - by ChrisV
    Just a quick question regarding an Azure application. If I have a number of Web and Worker roles that need to communicate, documentation says to use the Azure Queue Service. However, I've just read that the new .NET Service Bus now also offers queues. These look to be more powerful as they appear to offer a much more detailed API. Whilst the .NSB looks more interesting it has a couple of issues that make me wary of using it in distributed application. (for example, Queue Expiration... if I cannot guarantee that a queue will be renewed on time I may lose it all!). Has anyone had any experience using either of these two technologies and could give any advice on when to choose one over the other. I suspect that whilst the service bus looks more powerful, as my use case is really just enabling Web/Worker roles to communicate between each other, that the Azure Queue Service is what I'm after. But I'm just really looking for confirmation of that before progamming myself in to a corner :-) Thanks in advance. UPDATE Have read up about the two systems over the break. It defo looks like .NET service bus is more specifically designed for integrating systems rather than providing a general purpose reliable messaging system. Azure Queues are distributed and so reliable and scalable in a way that .NSB queues are not and so more suitable for code hosted within Azure itself. Thanks for the responses.

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  • Resumable Upload in Ruby on Rails

    - by user253011
    Hi, I have been searching for a way for resumable file upload in RoR. In conclusion, I found out other than Java Applet no client-side-and-cross-platform agent can access the file system in such a way that to request the file from the position where the upload got terminated (due to any reason) with some exceptions like http://github.com/taf2/resume-up/tree/master (built in native Ruby, but requires google gears which is not "reliable" yet when it comes to cross platform almost same story as of ActiveX!) Since the only reliable option left is java applet, is there any good tutorial/forum/documentation for those paid java applets, such as "thin slice upload" etc. to make it work with rails application. I have found one http : // github . com / dassi / mediaclue , its a non-multi-ligual-German-Application in which they used jumploader. But in that application, I am unable to see resumable functionality. Scratching my head against their documentation, i found out http : // jumploader.com / doc_resume.html It tells that jumploader has resume functionality in Cross session resume, the one i am looking for (if the user close the browser the new session gets hold on uncompleted uploaded files from the old session against the user id). But I cant find any example on their demos page which actually pause/RESUME functionality in a continuous manner! Is it even possible to achieve that kind of resumable functionality. Please tell me about any options/example/demos preferable deployed in rails. I shall be very much obliged. ~ Thanks

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  • OCR for low quality images

    - by dassouki
    Unfortunately, this is not CSI, we collected 20,000 images for license plates; we were wondering if there is a semi reliable way to read those license plates using OCR. the images especially night time ones are extremely low quality.

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  • Dovecot vs Courier vs Cyrus

    - by wag2639
    What is best for a Personal/SMB mail server running on an Ubuntu Server (8.04+)? I want to setup my own mail server at home to evaluate some options for my company before I make a recommendation. Which is the most secure, efficient, and reliable? Also, which is easiest to integrate with an LDAP and Calendar solution?

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  • How to transition to Comcast with static IP address

    - by steveha
    I have my own email server in my house, on a static IP address. I have had business DSL for over a decade, but I also now have Comcast business Internet. I want to transition from the DSL to the Comcast, and I have some questions. I have a domain name, my own mail server, and a firewall (a PC with two network interfaces, running Devil-Linux). I need to make sure I understand how to set up the Comcast cable box, and how to set up my firewall. First, do I need to change any settings in the cable box? Currently I have only used the cable box by plugging in a laptop, with the laptop doing DHCP. I think I can leave the box alone but I would like to make sure. Second, I'm not sure I understand the instructions Comcast gave me for setting up the firewall. My DSL provider gave me the following information: static IP address, net mask, gateway, and two DNS servers. Comcast gave me: static IP address, routable static IP address, net mask, and two DNS servers, and told me to put the "static IP address" as the "gateway" on the firewall. Is this just Comcast-speak here? Does "routable static IP address" mean the same thing as "static IP address" in my DSL setup, the end-point address that I should publish in the DNS MX records for my email server? Or should I publish the "static IP address", and Comcast will then route all its traffic over the cable box? My plan is: first, I'm going to configure another firewall, so I have one firewall for the DSL and one for the Comcast (rather than madly editing settings to switch back and forth). Then I will publish the new Comcast static IP address as a backup email server address in the DNS MX records, wait a while to let it propagate, and then switch my home over from the DSL to the Comcast. Then I'll change DNS to make that the primary mail address and the DSL the secondary, let that go a while and make sure it seems reliable. Then I'll remove the DSL from the DNS MX records completely, and finally shut down the DSL service. (I thought about keeping the DSL as a backup, but the reason I'm leaving DSL is that it has become unreliable; and I have heard that Comcast business Internet is reliable.) Final question, any advice for me? Anything you think might be useful, helpful, or educational. Thanks.

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  • How to transition to Comcast with static IP address [migrated]

    - by steveha
    I have my own email server in my house, on a static IP address. I have had business DSL for over a decade, but I also now have Comcast business Internet. I want to transition from the DSL to the Comcast, and I have some questions. I have a domain name, my own mail server, and a firewall (a PC with two network interfaces, running Devil-Linux). I need to make sure I understand how to set up the Comcast cable box, and how to set up my firewall. First, do I need to change any settings in the cable box? Currently I have only used the cable box by plugging in a laptop, with the laptop doing DHCP. I think I can leave the box alone but I would like to make sure. Second, I'm not sure I understand the instructions Comcast gave me for setting up the firewall. My DSL provider gave me the following information: static IP address, net mask, gateway, and two DNS servers. Comcast gave me: static IP address, routable static IP address, net mask, and two DNS servers, and told me to put the "static IP address" as the "gateway" on the firewall. Is this just Comcast-speak here? Does "routable static IP address" mean the same thing as "static IP address" in my DSL setup, the end-point address that I should publish in the DNS MX records for my email server? Or should I publish the "static IP address", and Comcast will then route all its traffic over the cable box? My plan is: first, I'm going to configure another firewall, so I have one firewall for the DSL and one for the Comcast (rather than madly editing settings to switch back and forth). Then I will publish the new Comcast static IP address as a backup email server address in the DNS MX records, wait a while to let it propagate, and then switch my home over from the DSL to the Comcast. Then I'll change DNS to make that the primary mail address and the DSL the secondary, let that go a while and make sure it seems reliable. Then I'll remove the DSL from the DNS MX records completely, and finally shut down the DSL service. (I thought about keeping the DSL as a backup, but the reason I'm leaving DSL is that it has become unreliable; and I have heard that Comcast business Internet is reliable.) Final question, any advice for me? Anything you think might be useful, helpful, or educational. Thanks.

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  • Mailing List Solution

    - by Shoaibi
    I have more than 1M users and i need to send newsletters to. I have tried PHPList but it has failed as it gets stalled every 30K emails. I need a faster and more reliable solution.

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  • Why is the vSphere console view so slow?

    - by blade
    Hi, Why is the Console view on the vSphere client so slow? It's a real shame because it's a shame to have to establish an RDP session every time you work on one of the VMs because of the speed of the console (I saw a tool to right click and open an RDP session to a VM in vSphere Client/ESX but this was not reliable). The Workstation console view is very smooth so I'd expect the vSphere Client console view to be very smooth. Thanks

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