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  • Stairway to T-SQL DML Level 10: Changing Data with the UPDATE Statement

    Unless you are working on a reporting-only application you will probably need to update tables in your SQL Server database. To update rows in a table you use the UPDATE statement. In this level we will be discussing how to find and update records in your database, and discuss the pitfalls you might run into when using the UPDATE statement. Is your SQL Database under Version Control?SSMS plug-in SQL Source Control connects SVN, TFS, Git, Hg and all others to SQL Server. Learn more.

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  • Going from webforms, VS 2008, 3.5 framework to the "next level" based on my goals

    - by Caveatrob
    I've got a few choices to make as I develop some business websites that will run for the next two to three years. Currently I run ASP.NET 3.5 with Visual Studio 2008. I do my development rather crudely in WebForms because that's what I learned and am most productive with. I don't use Membership or any other frameworks in my projects. I use a simple class that maintains a few session keys for each user based on basic database tables for users and roles. (I have about 3,000 users). So far I've kept the data simple, using ADO.NET against SQL Server and a data access class (Circa 2000, I know) to build my sites. My questions are as follows: Under what conditions would I be better off moving to MVC? Under what conditions would I find LINQ and ORM a better way to go than standard ADO.NET? Would I benefit, in my current state of development, from going from Studio 2008 to Studio 2010?

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  • xfce4 - 'Run Program' dialogue box does not appear when double clicking script

    - by Ron Paulfan
    Ubuntu 12.04 Xfce4 On my previous Ubuntu distro, when I double clicked scripts I got a little dialogue window that asked me if I wanted to run the script as a program or run it in terminal. Similar to this window: Since upgrading, I have never seen that window. I have ensured that the option to 'Allow executing as a program is enabled' and the script works if I run it through terminal. I simply just don't get the prompt. Any ideas?

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  • Run script at user login as root, with a catch

    - by tubaguy50035
    I'm trying to run a PHP script as root on user login. The PHP script adds a Samba share to the Samba config, thus the need for root privileges. The only issue here, is that the user doesn't exist yet. This system is integrated with active directory. So when a user logs in for the first time, a home directory for them is created under /home/DOMAIN/username. I've found this question and that seems like the correct way to get what I want, but I'm having trouble with the syntax since I don't know the user's name. Would it be something like: ALL ALL=(ALL) NOPASSWD: /home/DOMAIN/*/createSambaShare.php This doesn't seem to work as it is currently. Anyone have any ideas or a "scripted" way to add a Samba share on user login? Since I've made other changes to /etc/skel, I just added the bash necessary to run the PHP script in .profile in there. This then gets copied to the "new" user's home and it tries to run the PHP script. But it fails, because these are not privileged users. Changing permissions on the PHP script will not help. It needs to be run as sudo because it opens the Samba config file for writing. Letting any user run the PHP script would result in a PHP error. The homes Samba directive doesn't work for my use case. I need the Samba share to exist once they exist on the server, even when they're not logged in.

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  • How to run .run files? Not a root user

    - by user108056
    I have a Nvidia driver in my computer(Asus K55V Series) but it's missing the programe to run it so i can't use it. So i have downloaded the programe for nvidia through Http://www.nvidia.com/Download/index.aspx?lang=en-us but it's a .run file and i don't have programmes to run it. Product Type: GeForce Product Series: GeForce 600MSeries (Notebooks) Product: GeForce GT 630M Operating System: Linux 32bits (ubuntu) Language: I'm portuguese so i've selected Português (Brasil) but it doesn't really matter in the instalation. Help!

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  • Stairway to T-SQL DML Level 12: Using the MERGE Statement

    The final level of this stairway looks at the MERGE statement in detail, focusing on how to perform insert, update and delete logic using the MERGE statement. An accidental DBA? Try SQL MonitorUse the 30-day full product free trial to get easy-to-understand insights into SQL Server, and get suggestions on how to solve the type of issues that are uncovered. Begin your free trial.

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  • Taking too long to get skills for entry level programmer position [closed]

    - by greenonion
    I don't have the skills for an entry level position as a .Net programmer. I am trying to learn what I need but there is too much to learn and too little time. What can I do? About two months ago, I went to a job interview for an entry level C# .Net programming/consultant position in NYC. When I heard back from them, they told me that the knowledge gap between what I knew and what they needed me to know was too big and I might have been a better fit if I had 6 months of experience. This was the first interview that I went on since graduating college. before the interview, I read a book on visual C#. Turns out it wasn't a very good book and I was missing a lot of key areas of knowledge such as ADO.net SQL (I had learned some LINQ) A little bit about how memory is handled Multiple threaded programming, etc. Because the book wasn't very good, the stuff I did know, I didn't know very well. I felt crushed. I've applied for jobs to gain experience but when recruiters hear that I have no experience they lose interest. I figured that I can at least work on my knowledge. Since then, I read "SQL Essentials" to cover the SQL bit and I found a pretty awesome book that is good enough to clear up what's hazy in my mind and covers almost all of the extra topics. The book is "C# 4.0: The Complete Reference" by Herbert Schildt. I'm even learning a lot about the topics I was familiar with. For a month now I've been working my way through this beast of a book. However, gaining the knowledge I need is taking too long. I can't hold off not having a full-time job much longer. I'm not stupid and I'm studying constantly pouring through the book, asking questions on stackoverflow, referencing the C# specification, etc. I have made great progress but there is just too much ground to cover. I'm on chapter 12 which is about a 3rd through the book. To get an idea of what I know vs don't know, the table of contents is on amazon: http://www.amazon.com/C-4-0-The-Complete-Reference/dp/007174116X How on earth can someone know enough to function as a programmer in the real world? Can I try for a job in academia? Will I have time to finish learning the rest of the C# language or am I just un-hireable?

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  • Apache Traffic Server Gets Top-Level Project Status

    <b>Serverwatch:</b> "The Apache Software Foundation runs its open source projects on a hierarchy of principally three levels, top-level projects (TLPs), sub-projects and incubated projects. Achieving the TLP status is a major milestone for an open source effort and this week Apache announced that six projects were being graduated to TLP status."

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  • Run two shell file with thread

    - by user1149157
    How i can run two file shell in parallel and do not shared the same jvm. may be i use thread but how i run two file shell bu two thread ? File 1: #!/bin/bash # # Script for running several experimentations one the same JVM # Usage : TRACE_DIR NB_EXPE Factories... # param="parameter1" another="parameter2" for ((i = 10; i >= 0; i -= 1)) do echo "run my file with param another " done File 2 : #!/bin/bash # # Script for running several experimentations one the same JVM # Usage : TRACE_DIR NB_EXPE Factories... # a="101" b="400" c="500" echo "run my programme with a b c "

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  • Stairway to SQL Dialects Level 3: MySQL

    As part of the LAMP stack, MySQL is incredibly important for providing a reliable and platform-agnostic database platform for web development. This level looks at the syntax of MySQL and how to best port SQL code to a MySQL environment. NEW! The easiest way to deploy .NET codeDeploy ASP.NET applications fast, frequently, and without fuss, using Deployment Manager, the new tool from Red Gate. Try it now.

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  • Should entry level programmers be able to answer FizzBuzz?

    - by Bryan Rowe
    When interviewing entry level developers, I have used the FizzBuzz question as a type of acid test. Generally, I ask for a solution in pseudo-code or any language of their choice. If someone can't answer this question -- or get reasonably close, the interview generally ends shortly thereafter and we don't progress to more interesting code questions. In your opinion, is it fair/appropriate/accurate to filter entry-level staff in this manner? Should the average four year college graduate have a reasonable enough foundation to be able to throw up a pseudo-code solution of FizzBuzz?

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  • How to handle a player's level and its consequent privileges?

    - by Songo
    I'm building a game similar to Mafia Wars where a player can do tasks for his gang and gain experience and thus advancing his level. The game is built using PHP and a Mysql database. In the game I want to limit the resources allowed to player based on his level. For example: ________| (Max gold) | (Max army size) | (Max moves) | ... Level 1 | 1000 | 100 | 10 | ... Level 2 | 1500 | 200 | 20 | ... Level 3 | 3000 | 300 | 25 | ... . . . In addition certain features of the game won't be allowed until a certain level is reached such as players under Level 10 can't trade in the game market, players under Level 20 can't create alliances,...etc. The way I have modeled it is by implementing a very loooong ACL (Access Control List) with about 100 entries (an entry for each level). However, I think there may be a simpler approach to this seeing that this feature have been implemented in many games before.

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  • Algorithm for dynamically calculating a level based on experience points?

    - by George
    One of the struggles I've always had in game development is deciding how to implement experience points attributed to gaining a level. There doesn't seem to be a pattern to gaining a level in many of the games I've played, so I assume they have a static dictionary table which contains experience points vs. the level. e.g. Experience Level 0 1 100 2 175 3 280 4 800 5 ...There isn't a rhyme or reason why 280 points is equal to level 4, it just is. I'm not sure how those levels are decided, but it certainly wouldn't be dynamic. I've also thought about the possibility of exponential levels, as not to have to keep a separate lookup table, e.g. Experience Level 0 1 100 2 200 3 400 4 800 5 1600 6 3200 7 6400 8 ...but that seems like it would grow out of control rather quickly, as towards the upper levels, the enemies in the game would have to provide a whopping amount of experience to level -- and that would be to difficult to control. Leveling would become an impossible task. Does anyone have any pointers, or methods they use to decide how to level a character based on experience? I want to be fair in leveling and I want to stay ahead of the players as not to worry about constantly adding new experience/level lookups.

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  • How to create managed properties at site collection level in SharePoint2013

    - by ybbest
    In SharePoint2013, you can create managed properties at site collection. Today, I’d like to show you how to do so through PowerShell. 1. Define your managed properties and crawled properties and managed property Type in an external csv file. PowerShell script will read this file and create the managed and the mapping. 2. As you can see I also defined variant Type, this is because you need the variant type to create the crawled property. In order to have the crawled properties, you need to do a full crawl and also make sure you have data populated for your custom column. However, if you do not want to a full crawl to create those crawled properties, you can create them yourself by using the PowerShell; however you need to make sure the crawled properties you created have the same name if created by a full crawl. Managed properties type: Text = 1 Integer = 2 Decimal = 3 DateTime = 4 YesNo = 5 Binary = 6 Variant Type: Text = 31 Integer = 20 Decimal = 5 DateTime = 64 YesNo = 11 3. You can use the following script to create your managed properties at site collection level, the differences for creating managed property at site collection level is to pass in the site collection id. param( [string] $siteUrl="http://SP2013/", [string] $searchAppName = "Search Service Application", $ManagedPropertiesList=(IMPORT-CSV ".\ManagedProperties.csv") ) Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue $searchapp = $null function AppendLog { param ([string] $msg, [string] $msgColor) $currentDateTime = Get-Date $msg = $msg + " --- " + $currentDateTime if (!($logOnly -eq $True)) { # write to console Write-Host -f $msgColor $msg } # write to log file Add-Content $logFilePath $msg } $scriptPath = Split-Path $myInvocation.MyCommand.Path $logFilePath = $scriptPath + "\CreateManagedProperties_Log.txt" function CreateRefiner {param ([string] $crawledName, [string] $managedPropertyName, [Int32] $variantType, [Int32] $managedPropertyType,[System.GUID] $siteID) $cat = Get-SPEnterpriseSearchMetadataCategory –Identity SharePoint -SearchApplication $searchapp $crawledproperty = Get-SPEnterpriseSearchMetadataCrawledProperty -Name $crawledName -SearchApplication $searchapp -SiteCollection $siteID if($crawledproperty -eq $null) { Write-Host AppendLog "Creating Crawled Property for $managedPropertyName" Yellow $crawledproperty = New-SPEnterpriseSearchMetadataCrawledProperty -SearchApplication $searchapp -VariantType $variantType -SiteCollection $siteID -Category $cat -PropSet "00130329-0000-0130-c000-000000131346" -Name $crawledName -IsNameEnum $false } $managedproperty = Get-SPEnterpriseSearchMetadataManagedProperty -Identity $managedPropertyName -SearchApplication $searchapp -SiteCollection $siteID -ErrorAction SilentlyContinue if($managedproperty -eq $null) { Write-Host AppendLog "Creating Managed Property for $managedPropertyName" Yellow $managedproperty = New-SPEnterpriseSearchMetadataManagedProperty -Name $managedPropertyName -Type $managedPropertyType -SiteCollection $siteID -SearchApplication $searchapp -Queryable:$true -Retrievable:$true -FullTextQueriable:$true -RemoveDuplicates:$false -RespectPriority:$true -IncludeInMd5:$true } $mappedProperty = $crawledproperty.GetMappedManagedProperties() | ?{$_.Name -eq $managedProperty.Name } if($mappedProperty -eq $null) { Write-Host AppendLog "Creating Crawled -> Managed Property mapping for $managedPropertyName" Yellow New-SPEnterpriseSearchMetadataMapping -CrawledProperty $crawledproperty -ManagedProperty $managedproperty -SearchApplication $searchapp -SiteCollection $siteID } $mappedProperty = $crawledproperty.GetMappedManagedProperties() | ?{$_.Name -eq $managedProperty.Name } #Get-FASTSearchMetadataCrawledPropertyMapping -ManagedProperty $managedproperty } $searchapp = Get-SPEnterpriseSearchServiceApplication $searchAppName $site= Get-SPSite $siteUrl $siteId=$site.id Write-Host "Start creating Managed properties" $i = 1 FOREACH ($property in $ManagedPropertiesList) { $propertyName=$property.managedPropertyName $crawledName=$property.crawledName $managedPropertyType=$property.managedPropertyType $variantType=$property.variantType Write-Host $managedPropertyType Write-Host "Processing managed property $propertyName $($i)..." $i++ CreateRefiner $crawledName $propertyName $variantType $managedPropertyType $siteId Write-Host "Managed property created " $propertyName } Key Concepts Crawled Properties: Crawled properties are discovered by the search index service component when crawling content. Managed Properties: Properties that are part of the Search user experience, which means they are available for search results, advanced search, and so on, are managed properties. Mapping Crawled Properties to Managed Properties: To make a crawled property available for the Search experience—to make it available for Search queries and display it in Advanced Search and search results—you must map it to a managed property. References Administer search in SharePoint 2013 Preview Managing Metadata New-SPEnterpriseSearchMetadataCrawledProperty New-SPEnterpriseSearchMetadataManagedProperty Remove-SPEnterpriseSearchMetadataManagedProperty Overview of crawled and managed properties in SharePoint 2013 Preview Remove-SPEnterpriseSearchMetadataManagedProperty SharePoint 2013 – Search Service Application

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  • How to create managed properties at site collection level in SharePoint2013

    - by ybbest
    In SharePoint2013, you can create managed properties at site collection. Today, I’d like to show you how to do so through PowerShell. 1. Define your managed properties and crawled properties and managed property Type in an external csv file. PowerShell script will read this file and create the managed and the mapping. 2. As you can see I also defined variant Type, this is because you need the variant type to create the crawled property. In order to have the crawled properties, you need to do a full crawl and also make sure you have data populated for your custom column. However, if you do not want to a full crawl to create those crawled properties, you can create them yourself by using the PowerShell; however you need to make sure the crawled properties you created have the same name if created by a full crawl. Managed properties type: Text = 1 Integer = 2 Decimal = 3 DateTime = 4 YesNo = 5 Binary = 6 Variant Type: Text = 31 Integer = 20 Decimal = 5 DateTime = 64 YesNo = 11 3. You can use the following script to create your managed properties at site collection level, the differences for creating managed property at site collection level is to pass in the site collection id. param( [string] $siteUrl="http://SP2013/", [string] $searchAppName = "Search Service Application", $ManagedPropertiesList=(IMPORT-CSV ".\ManagedProperties.csv") ) Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue $searchapp = $null function AppendLog { param ([string] $msg, [string] $msgColor) $currentDateTime = Get-Date $msg = $msg + " --- " + $currentDateTime if (!($logOnly -eq $True)) { # write to console Write-Host -f $msgColor $msg } # write to log file Add-Content $logFilePath $msg } $scriptPath = Split-Path $myInvocation.MyCommand.Path $logFilePath = $scriptPath + "\CreateManagedProperties_Log.txt" function CreateRefiner {param ([string] $crawledName, [string] $managedPropertyName, [Int32] $variantType, [Int32] $managedPropertyType,[System.GUID] $siteID) $cat = Get-SPEnterpriseSearchMetadataCategory –Identity SharePoint -SearchApplication $searchapp $crawledproperty = Get-SPEnterpriseSearchMetadataCrawledProperty -Name $crawledName -SearchApplication $searchapp -SiteCollection $siteID if($crawledproperty -eq $null) { Write-Host AppendLog "Creating Crawled Property for $managedPropertyName" Yellow $crawledproperty = New-SPEnterpriseSearchMetadataCrawledProperty -SearchApplication $searchapp -VariantType $variantType -SiteCollection $siteID -Category $cat -PropSet "00130329-0000-0130-c000-000000131346" -Name $crawledName -IsNameEnum $false } $managedproperty = Get-SPEnterpriseSearchMetadataManagedProperty -Identity $managedPropertyName -SearchApplication $searchapp -SiteCollection $siteID -ErrorAction SilentlyContinue if($managedproperty -eq $null) { Write-Host AppendLog "Creating Managed Property for $managedPropertyName" Yellow $managedproperty = New-SPEnterpriseSearchMetadataManagedProperty -Name $managedPropertyName -Type $managedPropertyType -SiteCollection $siteID -SearchApplication $searchapp -Queryable:$true -Retrievable:$true -FullTextQueriable:$true -RemoveDuplicates:$false -RespectPriority:$true -IncludeInMd5:$true } $mappedProperty = $crawledproperty.GetMappedManagedProperties() | ?{$_.Name -eq $managedProperty.Name } if($mappedProperty -eq $null) { Write-Host AppendLog "Creating Crawled -> Managed Property mapping for $managedPropertyName" Yellow New-SPEnterpriseSearchMetadataMapping -CrawledProperty $crawledproperty -ManagedProperty $managedproperty -SearchApplication $searchapp -SiteCollection $siteID } $mappedProperty = $crawledproperty.GetMappedManagedProperties() | ?{$_.Name -eq $managedProperty.Name } #Get-FASTSearchMetadataCrawledPropertyMapping -ManagedProperty $managedproperty } $searchapp = Get-SPEnterpriseSearchServiceApplication $searchAppName $site= Get-SPSite $siteUrl $siteId=$site.id Write-Host "Start creating Managed properties" $i = 1 FOREACH ($property in $ManagedPropertiesList) { $propertyName=$property.managedPropertyName $crawledName=$property.crawledName $managedPropertyType=$property.managedPropertyType $variantType=$property.variantType Write-Host $managedPropertyType Write-Host "Processing managed property $propertyName $($i)..." $i++ CreateRefiner $crawledName $propertyName $variantType $managedPropertyType $siteId Write-Host "Managed property created " $propertyName } Key Concepts Crawled Properties: Crawled properties are discovered by the search index service component when crawling content. Managed Properties: Properties that are part of the Search user experience, which means they are available for search results, advanced search, and so on, are managed properties. Mapping Crawled Properties to Managed Properties: To make a crawled property available for the Search experience—to make it available for Search queries and display it in Advanced Search and search results—you must map it to a managed property. References Administer search in SharePoint 2013 Preview Managing Metadata

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  • two level tabs jquery

    - by telller
    I need to have two level tab navigation. Basically like this: Tab1 Tab2 Tab3 TabA TabB TabC When user clicks for example Tab2 he then can choose again from 2nd level tabs (TabA, TabB etc). I can make the first level ok but I can't make the 2nd level. How can i put it in the first level tabs.

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  • vb express / visual studio - is it possible to run / debug one form only in a multi form application

    - by Luay
    hi, I have a vb application consisting of several winForms and code files. Is it possible to run / debug only one form without having to run the whole application? To be more specific, one of the forms in my application is the settings form where the user sets his/her desired options. These options are read/written to an xml file. Is it possible to debug just this one form (and not the whole program) to see if the reading/writing went well, if everything displayed correctly... ? If I am thinking the wrong way about this, could you point me in the right direction? By the way, I am using visual basic express / visual studio.

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  • Best Practices - updated: which domain types should be used to run applications

    - by jsavit
    This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (formerly named Logical Domains). This is an updated and enlarged version of the post on this topic originally posted October 2012. One frequent question "what type of domain should I use to run applications?" There used to be a simple answer: "run applications in guest domains in almost all cases", but now there are more things to consider. Enhancements to Oracle VM Server for SPARC and introduction of systems like the current SPARC servers including the T4 and T5 systems, the Oracle SuperCluster T5-8 and Oracle SuperCluster M6-32 provide scale and performance much higher than the original servers that ran domains. Single-CPU performance, I/O capacity, memory sizes, are much larger now, and far more demanding applications are now being hosted in logical domains. The general advice continues to be "use guest domains in almost all cases", meaning, "use virtual I/O rather than physical I/O", unless there is a specific reason to use the other domain types. The sections below will discuss the criteria for choosing between domain types. Review: division of labor and types of domain Oracle VM Server for SPARC offloads management and I/O functionality from the hypervisor to domains (also called virtual machines), providing a modern alternative to older VM architectures that use a "thick", monolithic hypervisor. This permits a simpler hypervisor design, which enhances reliability, and security. It also reduces single points of failure by assigning responsibilities to multiple system components, further improving reliability and security. Oracle VM Server for SPARC defines the following types of domain, each with their own roles: Control domain - management control point for the server, runs the logical domain daemon and constraints engine, and is used to configure domains and manage resources. The control domain is the first domain to boot on a power-up, is always an I/O domain, and is usually a service domain as well. It doesn't have to be, but there's no reason to not leverage it for virtual I/O services. There is one control domain per T-series system, and one per Physical Domain (PDom) on an M5-32 or M6-32 system. M5 and M6 systems can be physically domained, with logical domains within the physical ones. I/O domain - a domain that has been assigned physical I/O devices. The devices may be one more more PCIe root complexes (in which case the domain is also called a root complex domain). The domain has native access to all the devices on the assigned PCIe buses. The devices can be any device type supported by Solaris on the hardware platform. a SR-IOV (Single-Root I/O Virtualization) function. SR-IOV lets a physical device (also called a physical function) or PF) be subdivided into multiple virtual functions (VFs) which can be individually assigned directly to domains. SR-IOV devices currently can be Ethernet or InfiniBand devices. direct I/O ownership of one or more PCI devices residing in a PCIe bus slot. The domain has direct access to the individual devices An I/O domain has native performance and functionality for the devices it owns, unmediated by any virtualization layer. It may also have virtual devices. Service domain - a domain that provides virtual network and disk devices to guest domains. The services are defined by commands that are run in the control domain. It usually is an I/O domain as well, in order for it to have devices to virtualize and serve out. Guest domain - a domain whose devices are all virtual rather than physical: virtual network and disk devices provided by one or more service domains. In common practice, this is where applications are run. Device considerations Consider the following when choosing between virtual devices and physical devices: Virtual devices provide the best flexibility - they can be dynamically added to and removed from a running domain, and you can have a large number of them up to a per-domain device limit. Virtual devices are compatible with live migration - domains that exclusively have virtual devices can be live migrated between servers supporting domains. On the other hand: Physical devices provide the best performance - in fact, native "bare metal" performance. Virtual devices approach physical device throughput and latency, especially with virtual network devices that can now saturate 10GbE links, but physical devices are still faster. Physical I/O devices do not add load to service domains - all the I/O goes directly from the I/O domain to the device, while virtual I/O goes through service domains, which must be provided sufficient CPU and memory capacity. Physical I/O devices can be other than network and disk - we virtualize network, disk, and serial console, but physical devices can be the wide range of attachable certified devices, including things like tape and CDROM/DVD devices. In some cases the lines are now blurred: virtual devices have better performance than previously: starting with Oracle VM Server for SPARC 3.1 there is near-native virtual network performance. There is more flexibility with physical devices than before: SR-IOV devices can now be dynamically reconfigured on domains. Tradeoffs one used to have to make are now relaxed: you can often have the flexibility of virtual I/O with performance that previously required physical I/O. You can have the performance and isolation of SR-IOV with the ability to dynamically reconfigure it, just like with virtual devices. Typical deployment A service domain is generally also an I/O domain: otherwise it wouldn't have access to physical device "backends" to offer to its clients. Similarly, an I/O domain is also typically a service domain in order to leverage the available PCI buses. Control domains must be I/O domains, because they boot up first on the server and require physical I/O. It's typical for the control domain to also be a service domain too so it doesn't "waste" the I/O resources it uses. A simple configuration consists of a control domain that is also the one I/O and service domain, and some number of guest domains using virtual I/O. In production, customers typically use multiple domains with I/O and service roles to eliminate single points of failure, as described in Availability Best Practices - Avoiding Single Points of Failure . Guest domains have virtual disk and virtual devices provisioned from more than one service domain, so failure of a service domain or I/O path or device does not result in an application outage. This also permits "rolling upgrades" in which service domains are upgraded one at a time while their guests continue to operate without disruption. (It should be noted that resiliency to I/O device failures can also be provided by the single control domain, using multi-path I/O) In this type of deployment, control, I/O, and service domains are used for virtualization infrastructure, while applications run in guest domains. Changing application deployment patterns The above model has been widely and successfully used, but more configuration options are available now. Servers got bigger than the original T2000 class machines with 2 I/O buses, so there is more I/O capacity that can be used for applications. Increased server capacity made it attractive to run more vertically-scaled applications, such as databases, with higher resource requirements than the "light" applications originally seen. This made it attractive to run applications in I/O domains so they could get bare-metal native I/O performance. This is leveraged by the Oracle SuperCluster engineered systems mentioned previously. In those engineered systems, I/O domains are used for high performance applications with native I/O performance for disk and network and optimized access to the Infiniband fabric. Another technical enhancement is Single Root I/O Virtualization (SR-IOV), which make it possible to give domains direct connections and native I/O performance for selected I/O devices. Not all I/O domains own PCI complexes, and there are increasingly more I/O domains that are not service domains. They use their I/O connectivity for performance for their own applications. However, there are some limitations and considerations: at this time, a domain using physical I/O cannot be live-migrated to another server. There is also a need to plan for security and introducing unneeded dependencies: if an I/O domain is also a service domain providing virtual I/O to guests, it has the ability to affect the correct operation of its client guest domains. This is even more relevant for the control domain. where the ldm command must be protected from unauthorized (or even mistaken) use that would affect other domains. As a general rule, running applications in the service domain or the control domain should be avoided. For reference, an excellent guide to secure deployment of domains by Stefan Hinker is at Secure Deployment of Oracle VM Server for SPARC. To recap: Guest domains with virtual I/O still provide the greatest operational flexibility, including features like live migration. They should be considered the default domain type to use unless there is a specific requirement that mandates an I/O domain. I/O domains can be used for applications with the highest performance requirements. Single Root I/O Virtualization (SR-IOV) makes this more attractive by giving direct I/O access to more domains, and by permitting dynamic reconfiguration of SR-IOV devices. Today's larger systems provide multiple PCIe buses - for example, 16 buses on the T5-8 - making it possible to configure multiple I/O domains each owning their own bus. Service domains should in general not be used for applications, because compromised security in the domain, or an outage, can affect domains that depend on it. This concern can be mitigated by providing guests' their virtual I/O from more than one service domain, so interruption of service in one service domain does not cause an application outage. The control domain should in general not be used to run applications, for the same reason. Oracle SuperCluster uses the control domain for applications, but it is an exception. It's not a general purpose environment; it's an engineered system with specifically configured applications and optimization for optimal performance. These are recommended "best practices" based on conversations with a number of Oracle architects. Keep in mind that "one size does not fit all", so you should evaluate these practices in the context of your own requirements. Summary Higher capacity servers that run Oracle VM Server for SPARC are attractive for applications with the most demanding resource requirements. New deployment models permit native I/O performance for demanding applications by running them in I/O domains with direct access to their devices. This is leveraged in SPARC SuperCluster, and can be leveraged in T-series servers to provision high-performance applications running in domains. Carefully planned, this can be used to provide peak performance for critical applications. That said, the improved virtual device performance in Oracle VM Server means that the default choice should still be guest domains with virtual I/O.

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  • Which isolation level should I use for the following insert-if-not-present transaction?

    - by Steve Guidi
    I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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