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  • Token based Authentication and Claims for Restful Services

    - by Your DisplayName here!
    WIF as it exists today is optimized for web applications (passive/WS-Federation) and SOAP based services (active/WS-Trust). While there is limited support for WCF WebServiceHost based services (for standard credential types like Windows and Basic), there is no ready to use plumbing for RESTful services that do authentication based on tokens. This is not an oversight from the WIF team, but the REST services security world is currently rapidly changing – and that’s by design. There are a number of intermediate solutions, emerging protocols and token types, as well as some already deprecated ones. So it didn’t make sense to bake that into the core feature set of WIF. But after all, the F in WIF stands for Foundation. So just like the WIF APIs integrate tokens and claims into other hosts, this is also (easily) possible with RESTful services. Here’s how. HTTP Services and Authentication Unlike SOAP services, in the REST world there is no (over) specified security framework like WS-Security. Instead standard HTTP means are used to transmit credentials and SSL is used to secure the transport and data in transit. For most cases the HTTP Authorize header is used to transmit the security token (this can be as simple as a username/password up to issued tokens of some sort). The Authorize header consists of the actual credential (consider this opaque from a transport perspective) as well as a scheme. The scheme is some string that gives the service a hint what type of credential was used (e.g. Basic for basic authentication credentials). HTTP also includes a way to advertise the right credential type back to the client, for this the WWW-Authenticate response header is used. So for token based authentication, the service would simply need to read the incoming Authorization header, extract the token, parse and validate it. After the token has been validated, you also typically want some sort of client identity representation based on the incoming token. This is regardless of how technology-wise the actual service was built. In ASP.NET (MVC) you could use an HttpModule or an ActionFilter. In (todays) WCF, you would use the ServiceAuthorizationManager infrastructure. The nice thing about using WCF’ native extensibility points is that you get self-hosting for free. This is where WIF comes into play. WIF has ready to use infrastructure built-in that just need to be plugged into the corresponding hosting environment: Representation of identity based on claims. This is a very natural way of translating a security token (and again I mean this in the widest sense – could be also a username/password) into something our applications can work with. Infrastructure to convert tokens into claims (called security token handler) Claims transformation Claims-based authorization So much for the theory. In the next post I will show you how to implement that for WCF – including full source code and samples. (Wanna learn more about federation, WIF, claims, tokens etc.? Click here.)

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  • Does the optimizer filter subqueries with outer where clauses

    - by Mongus Pong
    Take the following query: select * from ( select a, b from c UNION select a, b from d ) where a = 'mung' Will the optimizer generally work out that I am filtering a on the value 'mung' and consequently filter mung on each of the queries in the subquery. OR will it run each query within the subquery union and return the results to the outer query for filtering (as the query would perhaps suggest) In which case the following query would perform better : select * from ( select a, b from c where a = 'mung' UNION select a, b from d where a = 'mung' ) Obviously query 1 is best for maintenance, but is it sacrificing much performace for this? Which is best?

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  • Visual Website Optimizer and Code Igniter

    - by absentx
    We are trying to integrate visual website optimizer into a site of ours that uses Code Igniter. The problem is when we go into the VWO control panel to look at stats and previews nothing seems to be working. In the previews panel, all of them come up as code igniter error pages that say "The URI you submitted has disallowed characters." I have researched some solutions to this and have tried changing the regex in system/config to allow more characters, all characters etc and I am still having the problem. Any known issues or problems trying to integrate VWO and Code Igniter? This definitely seems to be a url issue but I can't nail it down.

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  • How do freelancers know how much their work is worth?

    - by Qmal
    I want to start a bit of freelancing in web development using ASP.NET MVC3 and PHP and I already have some people who are interested in hiring me, but I still can't figure out how much to charge for projects since I have never done it. For example how much would this site cost? Would it cost more if the author built it from scratch instead of using WordPress as the CMS? Or what about a simpler site like this? How much time spent is considered good/normal for building sites like these? And maybe some freelancers with experience can tell me what the usual requests are that they get from clients. What sites are the most in demand? I'm asking because I'm a student and I really can't work every day in a full-time job but I need the money so I guess a little freelancing would help me out.

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  • How do I justify upgrading to Windows Server 2008?

    - by thebunk
    We're just about to start a new greenfield project - it's a highly functional web application using ASP.NET MVC3, SQL Server etc. We're also going to be using Windows Workflow Foundation for the first time. Our client only wants to use his existing Windows Server 2003 web servers. My main issue (other than it is 8 years old) is that we don't much experierence of WWF development, but understand that using AppFabric (Server 2008 only) will improve WWF development. It's a significant cost to the client, as we need fail-over servers and a UAT environment as well. Am I correct in my understanding, and what methodologies can I use to justify the cost of upgrading?

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  • Basics of Join Factorization

    - by Hong Su
    We continue our series on optimizer transformations with a post that describes the Join Factorization transformation. The Join Factorization transformation was introduced in Oracle 11g Release 2 and applies to UNION ALL queries. Union all queries are commonly used in database applications, especially in data integration applications. In many scenarios the branches in a UNION All query share a common processing, i.e, refer to the same tables. In the current Oracle execution strategy, each branch of a UNION ALL query is evaluated independently, which leads to repetitive processing, including data access and join. The join factorization transformation offers an opportunity to share the common computations across the UNION ALL branches. Currently, join factorization only factorizes common references to base tables only, i.e, not views. Consider a simple example of query Q1. Q1:    select t1.c1, t2.c2    from t1, t2, t3    where t1.c1 = t2.c1 and t1.c1 > 1 and t2.c2 = 2 and t2.c2 = t3.c2   union all    select t1.c1, t2.c2    from t1, t2, t4    where t1.c1 = t2.c1 and t1.c1 > 1 and t2.c3 = t4.c3; Table t1 appears in both the branches. As does the filter predicates on t1 (t1.c1 > 1) and the join predicates involving t1 (t1.c1 = t2.c1). Nevertheless, without any transformation, the scan (and the filtering) on t1 has to be done twice, once per branch. Such a query may benefit from join factorization which can transform Q1 into Q2 as follows: Q2:    select t1.c1, VW_JF_1.item_2    from t1, (select t2.c1 item_1, t2.c2 item_2                   from t2, t3                    where t2.c2 = t3.c2 and t2.c2 = 2                                  union all                   select t2.c1 item_1, t2.c2 item_2                   from t2, t4                    where t2.c3 = t4.c3) VW_JF_1    where t1.c1 = VW_JF_1.item_1 and t1.c1 > 1; In Q2, t1 is "factorized" and thus the table scan and the filtering on t1 is done only once (it's shared). If t1 is large, then avoiding one extra scan of t1 can lead to a huge performance improvement. Another benefit of join factorization is that it can open up more join orders. Let's look at query Q3. Q3:    select *    from t5, (select t1.c1, t2.c2                  from t1, t2, t3                  where t1.c1 = t2.c1 and t1.c1 > 1 and t2.c2 = 2 and t2.c2 = t3.c2                 union all                  select t1.c1, t2.c2                  from t1, t2, t4                  where t1.c1 = t2.c1 and t1.c1 > 1 and t2.c3 = t4.c3) V;   where t5.c1 = V.c1 In Q3, view V is same as Q1. Before join factorization, t1, t2 and t3 must be joined first before they can be joined with t5. But if join factorization factorizes t1 from view V, t1 can then be joined with t5. This opens up new join orders. That being said, join factorization imposes certain join orders. For example, in Q2, t2 and t3 appear in the first branch of the UNION ALL query in view VW_JF_1. T2 must be joined with t3 before it can be joined with t1 which is outside of the VW_JF_1 view. The imposed join order may not necessarily be the best join order. For this reason, join factorization is performed under cost-based transformation framework; this means that we cost the plans with and without join factorization and choose the cheapest plan. Note that if the branches in UNION ALL have DISTINCT clauses, join factorization is not valid. For example, Q4 is NOT semantically equivalent to Q5.   Q4:     select distinct t1.*      from t1, t2      where t1.c1 = t2.c1  union all      select distinct t1.*      from t1, t2      where t1.c1 = t2.c1 Q5:    select distinct t1.*     from t1, (select t2.c1 item_1                   from t2                union all                   select t2.c1 item_1                  from t2) VW_JF_1     where t1.c1 = VW_JF_1.item_1 Q4 might return more rows than Q5. Q5's results are guaranteed to be duplicate free because of the DISTINCT key word at the top level while Q4's results might contain duplicates.   The examples given so far involve inner joins only. Join factorization is also supported in outer join, anti join and semi join. But only the right tables of outer join, anti join and semi joins can be factorized. It is not semantically correct to factorize the left table of outer join, anti join or semi join. For example, Q6 is NOT semantically equivalent to Q7. Q6:     select t1.c1, t2.c2    from t1, t2    where t1.c1 = t2.c1(+) and t2.c2 (+) = 2  union all    select t1.c1, t2.c2    from t1, t2      where t1.c1 = t2.c1(+) and t2.c2 (+) = 3 Q7:     select t1.c1, VW_JF_1.item_2    from t1, (select t2.c1 item_1, t2.c2 item_2                  from t2                  where t2.c2 = 2                union all                  select t2.c1 item_1, t2.c2 item_2                  from t2                                                                                                    where t2.c2 = 3) VW_JF_1       where t1.c1 = VW_JF_1.item_1(+)                                                                  However, the right side of an outer join can be factorized. For example, join factorization can transform Q8 to Q9 by factorizing t2, which is the right table of an outer join. Q8:    select t1.c2, t2.c2    from t1, t2      where t1.c1 = t2.c1 (+) and t1.c1 = 1 union all    select t1.c2, t2.c2    from t1, t2    where t1.c1 = t2.c1(+) and t1.c1 = 2 Q9:   select VW_JF_1.item_2, t2.c2   from t2,             (select t1.c1 item_1, t1.c2 item_2            from t1            where t1.c1 = 1           union all            select t1.c1 item_1, t1.c2 item_2            from t1            where t1.c1 = 2) VW_JF_1   where VW_JF_1.item_1 = t2.c1(+) All of the examples in this blog show factorizing a single table from two branches. This is just for ease of illustration. Join factorization can factorize multiple tables and from more than two UNION ALL branches.  SummaryJoin factorization is a cost-based transformation. It can factorize common computations from branches in a UNION ALL query which can lead to huge performance improvement. 

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  • best way to go about cost-benefit analysis on hardware

    - by Michael
    I'm looking to build a low-end computational server (my jargon in this field is especially limited so if someone can state that better please change that to meet jargon). I'm basically running computational fluid dynamics programs, large matrix computations and bioinformatics code. What would be the best way to approach cost/benefit analysis on what to put in the system? Perhaps even more general: How does one approach cost/benefit analysis on hardware theoretically (doing the analysis before building the machine)?

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  • Cost of running colour laser printers.

    - by Ian Ringrose
    Has anyone got a good list of the costs of running colour laser printers, both for colour and black that take into account different usage volumes. E.g if the dram needs replacing after 20,000 pages, but I am only do 10,000 in the next 3 years, I don’t care about the cost of a new dram. So a simple “cost per page” figure is each printer is not good enough to be useful in real life. (A spread sheet / website that I could type my own usage values into would be great.)

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  • why i add more insignificant code but cost less time

    - by user3714382
    i write a method and when i add some insignificant code it works faster, like these : array[1]=array[1]; array[0]=array[0]; array[3]=array[3]; array[2]=array[2]; i use double t=System.currentTimeMillis(); at first to record the time. then call the method and use System.out.println(System.currentTimeMillis()-t); in the end. when i delete the code (array[1]=array[1];...) the cost time is 1035.0 ms,but if i add these code, the cost time become 898.0ms. here is my method and my code. PS:this method is use for the game 2048, exp: {2,2,2,2} trans to {0,0,4,4} static void toRight2(int[] array){ if (array[2]==array[3] ) { array[3]=array[2]*2; if (array[0]==array[1]) { array[2]=array[1]*2; array[0]=0; array[1]=0; }else { array[2]=array[1]; array[1]=array[0]; array[0]=0; } } else{ if (array[0]==array[1]) { array[1]=array[1]*2; array[0]=0; array[3]=array[3]; array[2]=array[2]; }else { array[1]=array[1];//delete this cost more time array[0]=array[0];//delete this cost more time array[3]=array[3];//delete this cost more time array[2]=array[2];//delete this cost more time } } } public static void main(String[] args) { double t=System.currentTimeMillis(); int[] array={1,2,3,3}; for (int j = 2; j <400*1000000; j++) { toRight2(array); } System.out.println(System.currentTimeMillis()-t); }

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  • Configure Forms based authentication in SharePoint 2010

    - by sreejukg
      Configuring form authentication is a straight forward task in SharePoint. Mostly public facing websites built on SharePoint requires form based authentication. Recently, one of the WCM implementation where I was included in the project team required registration system. Any internet user can register to the site and the site offering them some membership specific functionalities once the user logged in. Since the registration open for all, I don’t want to store all those users in Active Directory. I have decided to use Forms based authentication for those users. This is a typical scenario of form authentication in SharePoint implementation. To implement form authentication you require the following A data store where you are storing the users – technically this can be active directory, SQL server database, LDAP etc. Form authentication will redirect the user to the login page, if the request is not authenticated. In the login page, there will be controls that validate the user inputs against the configured data store. In this article, I am going to use SQL server database with ASP.Net membership API’s to configure form based authentication in SharePoint 2010. This article assumes that you have SQL membership database available. I already configured the membership and roles database using aspnet_regsql command. If you want to know how to configure membership database using aspnet_regsql command, read the below blog post. http://weblogs.asp.net/sreejukg/archive/2011/06/16/usage-of-aspnet-regsql-exe-in-asp-net-4.aspx The snapshot of the database after implementing membership and role manager is as follows. I have used the database name “aspnetdb_claim”. Make sure you have created the database and make sure your database contains tables and stored procedures for membership. Create a web application with claims based authentication. This article assumes you already created a web application using claims based authentication. If you want to enable forms based authentication in SharePoint 2010, you must enable claims based authentication. Read this post for creating a web application using claims based authentication. http://weblogs.asp.net/sreejukg/archive/2011/06/15/create-a-web-application-in-sharepoint-2010-using-claims-based-authentication.aspx  You make sure, you have selected enable form authentication, and then selected Membership provider and Role manager name. To make sure you are done with the configuration, navigate to central administration website, from central administration, navigate to the Web Applications page, select the web application and click on icon, you will see the authentication providers for the current web application. Go to the section Claims authentication types, and make sure you have enabled forms based authentication. As mentioned in the snapshot, I have named the membership provider as SPFormAuthMembership and role manager as SPFormAuthRoleManager. You can choose your own names as you need. Modify the configuration files(Web.Config) to enable form authentication There are three applications that needs to be configured to support form authentication. The following are those applications. Central Administration If you want to assign permissions to web application using the credentials from form authentication, you need to update Central Administration configuration. If you do not want to access form authentication credentials from Central Administration, just leave this step.  STS service application Security Token service is the service application that issues security token when users are logging in. You need to modify the configuration of STS application to make sure users are able to login. To find the STS application, follow the following steps Go to the IIS Manager Expand the sites Node, you will see SharePoint Web Services Expand SharePoint Web Services, you can see SecurityTokenServiceApplication Right click SecuritytokenServiceApplication and click explore, it will open the corresponding file system. By default, the path for STS is C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\WebServices\SecurityToken You need to modify the configuration file available in the mentioned location. The web application that needs to be enabled with form authentication. You need to modify the configuration of your web application to make sure your web application identifies users from the form authentication.   Based on the above, I am going to modify the web configuration. At end of each step, I have mentioned the expected output. I recommend you to go step by step and after each step, make sure the configuration changes are working as expected. If you do everything all together, and test your application at the end, you may face difficulties in troubleshooting the configuration errors. Modifications for Central Administration Web.Config Open the web.config for the Central administration in a text editor. I always prefer Visual Studio, for editing web.config. In most cases, the path of the web.config for the central administration website is as follows C:\inetpub\wwwroot\wss\VirtualDirectories\<port number> Make sure you keep a backup copy of the web.config, before editing it. Let me summarize what we are going to do with Central Administration web.config. First I am going to add a connection string that points to the form authentication database, that I created as mentioned in previous steps. Then I need to add a membership provider and a role manager with the corresponding connectionstring. Then I need to update the peoplepickerwildcards section to make sure the users are appearing in search results. By default there is no connection string available in the web.config of Central Administration. Add a connection string just after the configsections element. The below is the connection string I have used all over the article. <add name="FormAuthConnString" connectionString="Initial Catalog=yourdatabasename;data source=databaseservername;Integrated Security=SSPI;" /> Once you added the connection string, the web.config look similar to Now add membership provider to the code. In web.config for CA, there will be <membership> tag, search for it. You will find membership and role manager under the <system.web> element. Under the membership providers section add the below code… <add name="SPFormAuthMembership" type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" applicationName="FormAuthApplication" connectionStringName="FormAuthConnString" /> After adding memberhip element, see the snapshot of the web.config. Now you need to add role manager element to the web.config. Insider providers element under rolemanager, add the below code. <add name="SPFormAuthRoleManager" type="System.Web.Security.SqlRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" applicationName="FormAuthApplication" connectionStringName="FormAuthConnString" /> After adding, your role manager will look similar to the following. As a last step, you need to update the people picker wildcard element in web.config, so that the users from your membership provider are available for browsing in Central Administration. Search for PeoplePickerWildcards in the web.config, add the following inside the <PeoplePickerWildcards> tag. <add key="SPFormAuthMembership" value="%" /> After adding this element, your web.config will look like After completing these steps, you can browse the users available in the SQL server database from central administration website. Go to the site collection administrator’s page from central administration. Select the site collection you have created for form authentication. Click on the people picker icon, choose Forms Auth and click on the search icon, you will see the users listed from the SQL server database. Once you complete these steps, make sure the users are available for browsing from central administration website. If you are unable to find the users, there must be some errors in the configuration, check windows event logs to find related errors and fix them. Change the web.config for STS application Open the web.config for STS application in text editor. By default, STS web.config does not have system.Web or connectionstrings section. Just after the System.Webserver element, add the following code. <connectionStrings> <add name="FormAuthConnString" connectionString="Initial Catalog=aspnetdb_claim;data source=sp2010_db;Integrated Security=SSPI;" /> </connectionStrings> <system.web> <roleManager enabled="true" cacheRolesInCookie="false" cookieName=".ASPXROLES" cookieTimeout="30" cookiePath="/" cookieRequireSSL="false" cookieSlidingExpiration="true" cookieProtection="All" createPersistentCookie="false" maxCachedResults="25"> <providers> <add name="SPFormAuthRoleManager" type="System.Web.Security.SqlRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" applicationName="FormAuthApplication" connectionStringName="FormAuthConnString" /> </providers> </roleManager> <membership userIsOnlineTimeWindow="15" hashAlgorithmType=""> <providers> <add name="SPFormAuthMembership" type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" applicationName="FormAuthApplication" connectionStringName="FormAuthConnString" /> </providers> </membership> </system.web> See the snapshot of the web.config after adding the required elements. After adding this, you should be able to login using the credentials from SQL server. Try assigning a user as primary/secondary administrator for your site collection from Central Administration and login to your site using form authentication. If you made everything correct, you should be able to login. This means you have successfully completed configuration of STS Configuration of Web Application for Form Authentication As a last step, you need to modify the web.config of the form authentication web application. Once you have done this, you should be able to grant permissions to users stored in the membership database. Open the Web.config of the web application you created for form authentication. You can find the web.config for the application under the path C:\inetpub\wwwroot\wss\VirtualDirectories\<port number> Basically you need to add connection string, membership provider, role manager and update the people picker wild card configuration. Add the connection string (same as the one you added to the web.config in Central Administration). See the screenshot after the connection string has added. Search for <membership> in the web.config, you will find this inside system.web element. There will be other providers already available there. You add your form authentication membership provider (similar to the one added to Central Administration web.config) to the provider element under membership. Find the snapshot of membership configuration as follows. Search for <roleManager> element in web.config, add the new provider name under providers section of the roleManager element. See the snapshot of web.config after new provider added. Now you need to configure the peoplepickerwildcard configuration in web.config. As I specified earlier, this is to make sure, you can locate the users by entering a part of their username. Add the following line under the <PeoplePickerWildcards> element in web.config. See the screenshot of the peoplePickerWildcards element after the element has been added. Now you have completed all the setup for form authentication. Navigate to the web application. From the site actions -> site settings -> go to peope and groups Click on new -> add users, it will popup the people picker dialog. Click on the icon, select Form Auth, enter a username in the search textbox, and click on search icon. See the screenshot of admin search when I tried searching the users If it displays the user, it means you are done with the configuration. If you add users to the form authentication database, the users will be able to access SharePoint portal as normal.

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  • 2D XNA Tile Based Lighting. Ideas and Methods

    - by Twitchy
    I am currently working on developing a 2D tile based game, similar to the game 'Terraria'. We have the base tile and chunk engine working and are now looking to implement lighting. Instead of the tile based lighting that terraria uses, I want to implement point lights for torches, etc. I have seen Catalin Zima’s shader based shadows, and this would be perfect for the torches (point lights). My problem here is that the tiles on the surface of the world need to be illuminated, doing this by a big point light is firstly extremely expensive, but also doesn't look right. What I need help with (overall) is... To have a surface that is illuminated regardless of torches, etc. To also have point lights, or smooth tile lighting similar to Catalin Zima’s shader based shadows. Looking forward to your replies. Any ideas are appreciated.

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  • Access-based Enumeration (December 04, 2009)

    - by user12612012
    Access-based Enumeration (ABE) is another recent addition to the Solaris CIFS Service - delivered into snv_124.  Designed to be compatible with Windows ABE, which was introduced in Windows Server 2003 SP1, this feature filters directory content based on the user browsing the directory.  Each user can only see the files and directories to which they have access.  This can be useful to implement an out-of-sight, out-of-mind policy or simply to reduce the number of files presented to each user - to make it easier to find files in directories containing a large number of files. ABE is managed on a per share basis by a new boolean share property called, as you might imagine, abe, which is described insharemgr(1M).  When set to true, ABE filtering is enabled on the share and directory entries to which the user has no access will be omitted from directory listings returned to the client.  When set to false or not defined, ABE filtering will not be performed on the share.  The abe property is not defined by default.Administration is straightforward, for example: # zfs sharesmb=abe=true,name=jane tank/home/jane# sharemgr show -vp    zfs       zfs/tank/home/jane nfs=() smb=()          jane=/export/home/jane     smb=(abe="true") ABE is also supported via sharemgr(1M) and on smbautohome(4) shares. Note that even though a file is visible in a share, with ABE enabled, it doesn't automatically mean that the user will always be able to open the file.  If a user has read attribute access to a file ABE will show the it but access will be denied if this user tries to open the file for reading or writing. We considered supporting ABE on NFS shares, as suggested by the name of PSARC/2009/375, but we ran into problems due to NFS client readdir caching.  NFS clients maintain a common directory entry cache for all users, which not only defeats the intent of ABE but can lead to very confusing results.  If multiple users are looking at the content of a directory with ABE enabled, the entries that get cached will depend on who looks at the directory first.  Subsequent users may see files that ABE on the server would have filtered out or files may be missing because they were filtered out for the original user. Although this issue can be resolved by disabling the NFS client readdir cache, this was deemed to be an unsuitable solution because it would create a dependency between a server share property and the configuration on all NFS clients, and there was the potential for differences in behavior across the various NFS clients.  It just seemed to add unnecessary administration complexity so we pulled it out. References for more information PSARC/2009/246 ZFS support for Access Based Enumeration PSARC/2009/375 ABE share property for NFS and SMB 6802734 Support for Access Based Enumeration 6802736 SMB share support for Access Based Enumeration Windows Access-based Enumeration

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  • HTG Explains: Photography with Film-Based Cameras

    - by Eric Z Goodnight
    We’ve become reliant on digital cameras since they are so easy to use. But have you ever wondered how film-based photography works? Read on to increase your photographic knowledge—or to develop an new appreciation for your point and click camera. Film-based cameras, to some, are a relic of the past. Simply an old technology made obsolete by the new and improved. But to many, film is an artisan’s material, and a photographic experience no digital system could hope to ever recreate. While many photographers, professional and amateur will swear by the quality of both film-based or digital cameras—the fact remains that film is still a valid way to take great photographs, and a fascinating way to learn more about how photography works.  HTG Explains: Photography with Film-Based CamerasHow to Clean Your Dirty Smartphone (Without Breaking Something)What is a Histogram, and How Can I Use it to Improve My Photos?

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  • Partition Wise Joins

    - by jean-pierre.dijcks
    Some say they are the holy grail of parallel computing and PWJ is the basis for a shared nothing system and the only join method that is available on a shared nothing system (yes this is oversimplified!). The magic in Oracle is of course that is one of many ways to join data. And yes, this is the old flexibility vs. simplicity discussion all over, so I won't go there... the point is that what you must do in a shared nothing system, you can do in Oracle with the same speed and methods. The Theory A partition wise join is a join between (for simplicity) two tables that are partitioned on the same column with the same partitioning scheme. In shared nothing this is effectively hard partitioning locating data on a specific node / storage combo. In Oracle is is logical partitioning. If you now join the two tables on that partitioned column you can break up the join in smaller joins exactly along the partitions in the data. Since they are partitioned (grouped) into the same buckets, all values required to do the join live in the equivalent bucket on either sides. No need to talk to anyone else, no need to redistribute data to anyone else... in short, the optimal join method for parallel processing of two large data sets. PWJ's in Oracle Since we do not hard partition the data across nodes in Oracle we use the Partitioning option to the database to create the buckets, then set the Degree of Parallelism (or run Auto DOP - see here) and get our PWJs. The main questions always asked are: How many partitions should I create? What should my DOP be? In a shared nothing system the answer is of course, as many partitions as there are nodes which will be your DOP. In Oracle we do want you to look at the workload and concurrency, and once you know that to understand the following rules of thumb. Within Oracle we have more ways of joining of data, so it is important to understand some of the PWJ ideas and what it means if you have an uneven distribution across processes. Assume we have a simple scenario where we partition the data on a hash key resulting in 4 hash partitions (H1 -H4). We have 2 parallel processes that have been tasked with reading these partitions (P1 - P2). The work is evenly divided assuming the partitions are the same size and we can scan this in time t1 as shown below. Now assume that we have changed the system and have a 5th partition but still have our 2 workers P1 and P2. The time it takes is actually 50% more assuming the 5th partition has the same size as the original H1 - H4 partitions. In other words to scan these 5 partitions, the time t2 it takes is not 1/5th more expensive, it is a lot more expensive and some other join plans may now start to look exciting to the optimizer. Just to post the disclaimer, it is not as simple as I state it here, but you get the idea on how much more expensive this plan may now look... Based on this little example there are a few rules of thumb to follow to get the partition wise joins. First, choose a DOP that is a factor of two (2). So always choose something like 2, 4, 8, 16, 32 and so on... Second, choose a number of partitions that is larger or equal to 2* DOP. Third, make sure the number of partitions is divisible through 2 without orphans. This is also known as an even number... Fourth, choose a stable partition count strategy, which is typically hash, which can be a sub partitioning strategy rather than the main strategy (range - hash is a popular one). Fifth, make sure you do this on the join key between the two large tables you want to join (and this should be the obvious one...). Translating this into an example: DOP = 8 (determined based on concurrency or by using Auto DOP with a cap due to concurrency) says that the number of partitions >= 16. Number of hash (sub) partitions = 32, which gives each process four partitions to work on. This number is somewhat arbitrary and depends on your data and system. In this case my main reasoning is that if you get more room on the box you can easily move the DOP for the query to 16 without repartitioning... and of course it makes for no leftovers on the table... And yes, we recommend up-to-date statistics. And before you start complaining, do read this post on a cool way to do stats in 11.

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  • Microsoft VDI 2012 - VDI Personal collection vs Session-based deployment

    - by Vazgen
    I have a small confusion about the differences between the 2 types of set ups: When deploying using Add Roles and Features the Wizard requests to choose from one of two Deployment Scenarios: Virtual machine-based desktop deployment : Virtual machine-based desktop deployment allows users to connect to virtual desktop collections that include published RemoteApp programs and virtual desktops. Session-based desktop deployment : Session-based desktop deployment allows users to connect to session collections that include published RemoteApp programs and session-based desktops. Although this seems intuitive now, if I continue with "Virtual machine-based desktop deployment" I later have another two options when creating a collection: Pooled virtual desktop collection Personal virtual desktop collection This is where my confusion lies. What is the differences between a Session-based deployment and Virtual machine-based deployment with Personal virtual desktop collections? I'm mostly finding information pertaining to Windows Server 2008 but I know there are some core improvements in VDI 2012 so would someone please comment on that. Thank you

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