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  • Calculating estimated data loss with Always on

    - by blakmk
    Ever wondered how calculate estimated data loss (time) for always on. The metric in the always on dashboard shows the metric quite nicely but there does seem to be a lack of documentation about where the metrics ---come from. Heres a script that calculates the data loss ( lag ) so you can set up alerts based on your DR SLA's:       WITH DR_CTE ( replica_server_name, database_name, last_commit_time) AS                 (                                 select ar.replica_server_name, database_name, rs.last_commit_time                                 from master.sys.dm_hadr_database_replica_states  rs                                 inner join master.sys.availability_replicas ar on rs.replica_id = ar.replica_id                                 inner join sys.dm_hadr_database_replica_cluster_states dcs on dcs.group_database_id = rs.group_database_id and rs.replica_id = dcs.replica_id                                 where replica_server_name != @@servername                 ) select ar.replica_server_name, dcs.database_name, rs.last_commit_time, DR_CTE.last_commit_time 'DR_commit_time', datediff(ss,  DR_CTE.last_commit_time, rs.last_commit_time) 'lag_in_seconds' from master.sys.dm_hadr_database_replica_states  rs inner join master.sys.availability_replicas ar on rs.replica_id = ar.replica_id inner join sys.dm_hadr_database_replica_cluster_states dcs on dcs.group_database_id = rs.group_database_id and rs.replica_id = dcs.replica_id inner join DR_CTE on DR_CTE.database_name = dcs.database_name where ar.replica_server_name = @@servername order by lag_in_seconds desc

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  • The Interaction between Three-Tier Client/Server Model and Three-Tier Application Architecture Model

    The three-tier client/server model is a network architectural approach currently used in modern networking. This approach divides a network in to three distinct components. Three-Tier Client/Server Model Components Client Component Server Component Database Component The Client Component of the network typically represents any device on the network. A basic example of this would be computer or another network/web enabled devices that are connected to a network. Network clients request resources on the network, and are usually equipped with a user interface for the presentation of the data returned from the Server Component. This process is done through the use of various software clients, and example of this can be seen through the use of a web browser client. The web browser request information from the Server Component located on the network and then renders the results for the user to process. The Server Components of the network return data based on specific client request back to the requesting client.  Server Components also inherit the attributes of a Client Component in that they are a device on the network and that they can also request information from other Server Components. However what differentiates a Client Component from a Server Component is that a Server Component response to requests from devices on the network. An example of a Server Component can be seen in a web server. A web server listens for new requests and then interprets the request, processes the web pages, and then returns the processed data back to the web browser client so that it may render the data for the user to interpret. The Database Component of the network returns unprocessed data from databases or other resources. This component also inherits attributes from the Server Component in that it is a device on a network, it can request information from other server components and database components, and it also listens for new requests so that it can return data when needed. The three-tier client/server model is very similar to the three-tier application architecture model, and in fact the layers can be mapped to one another. Three-Tier Application Architecture Model Presentation Layer/Logic Business Layer/Logic Data Layer/Logic The Presentation Layer including its underlying logic is very similar to the Client Component of the three-tiered model. The Presentation Layer focuses on interpreting the data returned by the Business Layer as well as presents the data back to the user.  Both the Presentation Layer and the Client Component focus primarily on the user and their experience. This allows for segments of the Business Layer to be distributable and interchangeable because the Presentation Layer is not directly integrated in with Business Layer. The Presentation Layer does not care where the data comes from as long as it is in the proper format. This allows for the Presentation Layer and Business Layer to be stored on one or more different servers so that it can provide a higher availability to clients requesting data. A good example of this is a web site that uses load balancing. When a web site decides to take on the task of load balancing they must obtain a network device that sits in front of a one or machines in order to distribute the request across multiple servers. When a user comes in through the load balanced device they are redirected to a specific server based on a few factors. Common Load Balancing Factors Current Server Availability Current Server Response Time Current Server Priority The Business Layer and corresponding logic are business rules applied to data prior to it being sent to the Presentation Layer. These rules are used to manipulate the data coming from the Data Access Layer, in addition to validating any data prior to being stored in the Data Access Layer. A good example of this would be when a user is trying to create multiple accounts under one email address. The Business Layer logic can prevent duplicate accounts by enforcing a unique email for every new account before the data is even stored in the Data Access Layer. The Server Component can be directly tied to this layer in that the server typically stores and process the Business Layer before it is returned to the end-user via the Presentation Layer. In addition the Server Component can also run automated process through the Business Layer on the data in the Data Access Layer so that additional business analysis can be derived from the data that has been already collected. The Data Layer and its logic are responsible for storing information so that it can be easily retrieved. Typical in most modern applications data is stored in a database management system however data can also be in the form of files stored on a file server. In addition a database can take on one of several forms. Common Database Formats XML File Pipe Delimited File Tab Delimited File Comma Delimited File (CSV) Plain Text File Microsoft Access Microsoft SQL Server MySql Oracle Sybase The Database component of the Networking model can be directly tied to the Data Layer because this is where the Data Layer obtains the data to return back the Business Layer. The Database Component basically allows for a place on the network to store data for future use. This enables applications to save data when they can and then quickly recall the saved data as needed so that the application does not have to worry about storing the data in memory. This prevents overhead that could be created when an application must retain all data in memory. As you can see the Three-Tier Client/Server Networking Model and the Three-Tiered Application Architecture Model rely very heavily on one another to function especially if different aspects of an application are distributed across an entire network. The use of various servers and database servers are wonderful when an application has a need to distribute work across the network. Network Components and Application Layers Interaction Database components will store all data needed for the Data Access Layer to manipulate and return to the Business Layer Server Component executes the Business Layer that manipulates data so that it can be returned to the Presentation Layer Client Component hosts the Presentation Layer that  interprets the data and present it to the user

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  • Oracle Healthcare Data Warehouse Foundations RELEASED!

    - by Glen McCallum
    Since I joined Oracle I've been working on Oracle Healthcare Data Warehouse Foundations (OHDF). It was officially released earlier this month at HIMSS. But for over 2 months prior to that I had to keep it a secret. It was so tough; I didn't even tell my family when they asked me what I was working on. Anyway, OHDF is an enterprise healthcare data model. Unlike Healthcare Transaction Base, OHDF is in 3rd normal form. It is logical and reasonably easy to understand for anyone with some experience in the healthcare domain. OHDF is emerging as the core of Oracle's healthcare business intelligence applications.

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  • Connecting to Microsoft Excel using Oracle Data Integrator

    - by julien.testut
    The posts in this series assume that you have some level of familiarity with ODI. The concepts of Topology, Data Server, Physical and Logical Architecture are used here assuming that you understand them in the context of ODI. If you need more details on these elements, please refer to the ODI Tutorial for a quick introduction, or to the complete ODI documentation for more details. In this post I will describe how a Microsoft Excel spreadsheet can be used in Oracle Data Integrator. Microsoft Excel is one of the many different technologies you can leverage in ODI as a source or as a target. Prepare your Excel spreadsheet Prior to using a Microsoft Excel spreadsheet in ODI we need to specify a name for the different cell tables we want to use. You can have multiple names in the same spreadsheet. First open up a Microsoft Excel spreadsheet, we will need to define a named range.

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  • OWB 11gR2 &ndash; Flexible and extensible

    - by David Allan
    The Oracle data integration extensibility capabilities are something I love, nothing more frustrating than a tool or platform that is very constraining. I think extensibility and flexibility are invaluable capabilities in the data integration arena. I liked Uli Bethke's posting on some extensibility capabilities with ODI (see Nesting ODI Substitution Method Calls here), he has some useful guidance on making customizations to existing KMs, nice to learn by example. I thought I'd illustrate the same capabilities with ODI's partner OWB for the OWB community. There is a whole new world of potential. The LKM/IKM/CKM/JKMs are the primary templates that are supported (plus the Oracle Target code template), so there is a lot of potential for customizing and extending the product in this release. Enough waffle... Diving in at the deep end from Uli's post, in OWB the table operator has a number of additional properties in OWB 11gR2 that let you annotate the column usage with ODI-like properties such as the slowly changing usage or for your own user-defined purpose as in Uli's post, below you see for the target table SALES_TARGET we can use the UD5 property which when assigned the code template (knowledge module) which has been modified with Uli's change we can do custom things such as creating indices - provides The code template used by the mapping has the additional step which is basically the code illustrated from Uli's posting just used directly, the ODI 10g substitution references also supported from within OWB's runtime. Now to see whether this does what we expect before we execute it, we can check out the generated code similar to how the traditional mapping generation and preview works, you do this by clicking on the 'Inspect Code' button on the execution units code template assignment. This then  creates another tab with prefix 'Code - <mapping name>' where the generated code is put, scrolling down we find the last step with the indices being created, looks good, so we are ready to deploy and execute. After executing the mapping we can then use the 'Audit Information' panel (select the mapping in the designer tree and click on View/Audit Information), this gives us a view of the execution where we can drill into the tasks that were executed and inspect both the template and the generated code that was executed and any potential errors. Reflecting back on earlier versions of OWB, these were the kinds of features that were always highly desirable, getting under the hood of the code generation and tweaking bit and pieces - fun and powerful stuff! We can step it up a bit here and explore some further ideas. The example below is a daisy-chained set of execution units where the intermediate table is a target of one unit and the source for another. We want that table to be a global temporary table, so can tweak the templates. Back to the copy of SQL Control Append (for demo purposes) we modify the create target table step to make the table a global temporary table, with the option of on commit preserve rows. You can get a feel for some of the customizations and changes possible, providing some great flexibility and extensibility for the data integration tools.

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  • Adding an expression based image in a client report definition file (RDLC)

    - by rajbk
    In previous posts, I showed you how to create a report using Visual Studio 2010 and how to add a hyperlink to the report.  In this post, I show you how to add an expression based image to each row of the report. This similar to displaying a checkbox column for Boolean values.  A sample project is attached to the bottom of this post. To start off, download the project we created earlier from here.  The report we created had a “Discontinued” column of type Boolean. We are going to change it to display an “available” icon or “unavailable” icon based on the “Discontinued” row value.    Load the project and double click on Products.rdlc. With the report design surface active, you will see the “Report Data” tool window. Right click on the Images folder and select “Add Image..”   Add the available_icon.png and discontinued_icon.png images (the sample project at the end of this post has the icon png files)    You can see the images we added in the “Report Data” tool window.   Drag and drop the available_icon into the “Discontinued” column row (not the header) We get a dialog box which allows us to set the image properties. We will add an expression that specifies the image to display based the “Discontinued” value from the Product table. Click on the expression (fx) button.   Add the following expression : = IIf(Fields!Discontinued.Value = True, “discontinued_icon”, “available_icon”)   Save and exit all dialog boxes. In the report design surface, resize the column header and change the text from “Discontinued” to “In Production”.   (Optional) Right click on the image cell (not header) , go to “Image Properties..” and offset it by 5pt from the left. (Optional) Change the border color since it is not set by default for image columns. We are done adding our image column! Compile the application and run it. You will see that the “In Production” column has red ‘x’ icons for discontinued products. Download the VS 2010 sample project NorthwindReportsImage.zip Other Posts Adding a hyperlink in a client report definition file (RDLC) Rendering an RDLC directly to the Response stream in ASP.NET MVC ASP.NET MVC Paging/Sorting/Filtering using the MVCContrib Grid and Pager Localization in ASP.NET MVC 2 using ModelMetadata Setting up Visual Studio 2010 to step into Microsoft .NET Source Code Running ASP.NET Webforms and ASP.NET MVC side by side Pre-filtering and shaping OData feeds using WCF Data Services and the Entity Framework

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  • Web Development Trends: Mobile First, Data-Oriented Development, and Single Page Applications

    - by dwahlin
    I recently had the opportunity to give a keynote talk at an Intel conference about key trends in the world of Web development that I feel teams should be taking into account with projects. It was a lot of fun and I had the opportunity to talk with a lot of different people about projects they’re working on. There are a million things that could be covered for this type of talk (HTML5 anyone?) but I only had 60 minutes and couldn’t possibly cover them all so I decided to focus on 3 key areas: mobile, data-oriented development, and SPAs. The talk was geared toward introducing people (many who weren’t Web developers) to topics such as mobile first development (demos showed a few tools to help here), responsive design techniques, data binding techniques that can simplify code, and Single Page Application (SPA) benefits. Links to code demos shown during the presentation can be found at the end of the slide deck. Web Development Trends - What's New in the World of Web Development by Dan Wahlin

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  • mysql show databases not showing databases that are in /opt/bitnami/mysql/data directory

    - by hgolov
    and thank you for taking the time to look at my question. I have an ebs-backed ec2 ubuntu server which is running but unreachable. ** There are very stupidly no recent backups ** I made a snapshot of the block, created a volume, spun up a new instance, attached the new volume. I see all the data from my site in the /opt/bitnami/mysql/data directory, but when I go into the mysql console, it shows only information_schema and test when I type show databases; How can I 'point' mysql to the correct folder? Thank you!

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  • Dynamic Data Connections

    - by Tim Dexter
    I have had a long running email thread running between Dan and David over at Valspar and myself. They have built some impressive connectivity between their in house apps and BIP using web services. The crux of their problem has been that they have multiple databases that need the same report executed against them. Not such an unusual request as I have spoken to two customers in the last month with the same situation. Of course, you could create a report against each data connection and just run or call the appropriate report. Not too bad if you have two or three data connections but more than that and it becomes a maintenance nightmare having to update queries or layouts. Ideally you want to have just a single report definition on the BIP server and to dynamically set the connection to be used at runtime based on the user or system that the user is in. A quick bit of digging and help from Shinji on the development team and I had an answer. Rather embarassingly, the solution has been around since the Oct 2010 rollup patch last year. Still, I grabbed the latest Jan 2011 patch - check out Note 797057.1 for the latest available patches. Once installed, I used the best web service testing tool I have yet to come across - SoapUI. Just point it at the WSDL and you can check out the available services and their parameters and then test them too. The XML packet has a new dynamic data source entry. You can set you own custom JDBC connection or just specify an existing data source name thats defined on the server. <pub:runReport> <pub:reportRequest> <pub:attributeFormat>xml</pub:attributeFormat> <pub:attributeTemplate>0</pub:attributeTemplate> <pub:byPassCache>true</pub:byPassCache> <pub:dynamicDataSource> <pub:JDBCDataSource> <pub:JDBCDriverClass></pub:JDBCDriverClass> <pub:JDBCDriverType></pub:JDBCDriverType> <pub:JDBCPassword></pub:JDBCPassword> <pub:JDBCURL></pub:JDBCURL> <pub:JDBCUserName></pub:JDBCUserName> <pub:dataSourceName>Conn1</pub:dataSourceName> </pub:JDBCDataSource> </pub:dynamicDataSource> <pub:reportAbsolutePath>/Test/Employee Report/Employee Report.xdo</pub:reportAbsolutePath> </pub:reportRequest> <pub:userID>Administrator</pub:userID> <pub:password>Administrator</pub:password> </pub:runReport> So I have Conn1 and Conn2 defined that are connections to different databases. I can just flip the name, make the WS call and get the appropriate dataset in my report. Just as an example, here's my web service call java code. Just a case of bringing in the BIP java libs to my java project. publicReportServiceService = new PublicReportServiceService(); PublicReportService publicReportService = publicReportServiceService.getPublicReportService_v11(); String userID = "Administrator"; String password = "Administrator"; ReportRequest rr = new ReportRequest(); rr.setAttributeFormat("xml"); rr.setAttributeTemplate("1"); rr.setByPassCache(true); rr.setReportAbsolutePath("/Test/Employee Report/Employee Report.xdo"); rr.setReportOutputPath("c:\\temp\\output.xml"); BIPDataSource bipds = new BIPDataSource(); JDBCDataSource jds = new JDBCDataSource(); jds.setDataSourceName("Conn1"); bipds.setJDBCDataSource(jds); rr.setDynamicDataSource(bipds); try { publicReportService.runReport(rr, userID, password); } catch (InvalidParametersException e) { e.printStackTrace(); } catch (AccessDeniedException e) { e.printStackTrace(); } catch (OperationFailedException e) { e.printStackTrace(); } } Note, Im no java whiz kid or whizzy old bloke, at least not unless Ive had a coffee. JDeveloper has a nice feature where you point it at the WSDL and it creates everything to support your calling code for you. Couple of things to remember: 1. When you call the service, remember to set the bypass the cache option. Forget it and much scratching of your head and taking my name in vain will ensue. 2. My demo actually hit the same database but used two users, one accessed the base tables another views with the same name. For far too long I thought the connection swapping was not working. I was getting the same results for both users until I realized I was specifying the schema name for the table/view in my query e.g. select * from EMP.EMPLOYEES. So remember to have a generic query that will depend entirely on the connection. Its a neat feature if you want to be able to switch connections and only define a single report and call it remotely. Now if you want the connection to be set dynamically based on the user and the report run via the user interface, thats going to be more tricky ... need to think about that one!

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  • Database Machine, 11gR2 és a Tivoli Data Protection is együttmuködik

    - by Fekete Zoltán
    Felmerült a kérdés, hogy a Database Machine környezetben végezhetjük-e a mentéseket Tivoli Data Protection for Oracle szoftverrel. A válasz: IGEN. Az IBM Tivoli Data Protection for Oracle V5.5.2 on Linux x86_64 immár bevizsgáltatott az Oracle 11gR2 RAC-cal. Az aktuális support információ itt található: A V5.5.2-re kattintva megtaláljátok a következo adatokat: Oracle Enterprise Linux 5 with any of the following Oracle releases: * 64-bit Oracle Standard or Enterprise Server 10gR2, 11g, or 11gR2 * 64-bit Real Application Clusters (RAC) 10gR2, 11g, or 11gR2 Ez az információ elegendo és remek :), mivel a Database Machine komponensek Oracle Enterprise Linux operációs rendszeren muködnek, 64 bites architektúrában és az Oracle RMAN (Recovery Manager) elemet tudja használni a TDP.

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  • Retrieve Performance Data from SOA Infrastructure Database

    - by fip
    My earlier blog posting shows how to enable, retrieve and interpret BPEL engine performance statistics to aid performance troubleshooting. The strength of BPEL engine statistics at EM is its break down per request. But there are some limitations with the BPEL performance statistics mentioned in that blog posting: The statistics were stored in memory instead of being persisted. To avoid memory overflow, the data are stored to a buffer with limited size. When the statistic entries exceed the limitation, old data will be flushed out to give ways to new statistics. Therefore it can only keep the last X number of entries of data. The statistics 5 hour ago may not be there anymore. The BPEL engine performance statistics only includes latencies. It does not provide throughputs. Fortunately, Oracle SOA Suite runs with the SOA Infrastructure database and a lot of performance data are naturally persisted there. It is at a more coarse grain than the in-memory BPEL Statistics, but it does have its own strengths as it is persisted. Here I would like offer examples of some basic SQL queries you can run against the infrastructure database of Oracle SOA Suite 11G to acquire the performance statistics for a given period of time. You can run it immediately after you modify the date range to match your actual system. 1. Asynchronous/one-way messages incoming rates The following query will show number of messages sent to one-way/async BPEL processes during a given time period, organized by process names and states select composite_name composite, state, count(*) Count from dlv_message where receive_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; 2. Throughput of BPEL process instances The following query shows the number of synchronous and asynchronous process instances created during a given time period. It list instances of all states, including the unfinished and faulted ones. The results will include all composites cross all SOA partitions select state, count(*) Count, composite_name composite, component_name,componenttype from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype order by count(*) desc; 3. Throughput and latencies of BPEL process instances This query is augmented on the previous one, providing more comprehensive information. It gives not only throughput but also the maximum, minimum and average elapse time BPEL process instances. select composite_name Composite, component_name Process, componenttype, state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;   4. Combine all together Now let's combine all of these 3 queries together, and parameterize the start and end time stamps to make the script a bit more robust. The following script will prompt for the start and end time before querying against the database: accept startTime prompt 'Enter start time (YYYY-MM-DD HH24:MI:SS)' accept endTime prompt 'Enter end time (YYYY-MM-DD HH24:MI:SS)' Prompt "==== Rejected Messages ===="; REM 2012-10-24 21:00:00 REM 2012-10-24 21:59:59 select count(*), composite_dn from rejected_message where created_time >= to_timestamp('&&StartTime','YYYY-MM-DD HH24:MI:SS') and created_time <= to_timestamp('&&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_dn; Prompt " "; Prompt "==== Throughput of one-way/asynchronous messages ===="; select state, count(*) Count, composite_name composite from dlv_message where receive_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; Prompt " "; Prompt "==== Throughput and latency of BPEL process instances ====" select state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime, composite_name Composite, component_name Process, componenttype from cube_instance where creation_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;  

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  • Why lock-free data structures just aren't lock-free enough

    - by Alex.Davies
    Today's post will explore why the current ways to communicate between threads don't scale, and show you a possible way to build scalable parallel programming on top of shared memory. The problem with shared memory Soon, we will have dozens, hundreds and then millions of cores in our computers. It's inevitable, because individual cores just can't get much faster. At some point, that's going to mean that we have to rethink our architecture entirely, as millions of cores can't all access a shared memory space efficiently. But millions of cores are still a long way off, and in the meantime we'll see machines with dozens of cores, struggling with shared memory. Alex's tip: The best way for an application to make use of that increasing parallel power is to use a concurrency model like actors, that deals with synchronisation issues for you. Then, the maintainer of the actors framework can find the most efficient way to coordinate access to shared memory to allow your actors to pass messages to each other efficiently. At the moment, NAct uses the .NET thread pool and a few locks to marshal messages. It works well on dual and quad core machines, but it won't scale to more cores. Every time we use a lock, our core performs an atomic memory operation (eg. CAS) on a cell of memory representing the lock, so it's sure that no other core can possibly have that lock. This is very fast when the lock isn't contended, but we need to notify all the other cores, in case they held the cell of memory in a cache. As the number of cores increases, the total cost of a lock increases linearly. A lot of work has been done on "lock-free" data structures, which avoid locks by using atomic memory operations directly. These give fairly dramatic performance improvements, particularly on systems with a few (2 to 4) cores. The .NET 4 concurrent collections in System.Collections.Concurrent are mostly lock-free. However, lock-free data structures still don't scale indefinitely, because any use of an atomic memory operation still involves every core in the system. A sync-free data structure Some concurrent data structures are possible to write in a completely synchronization-free way, without using any atomic memory operations. One useful example is a single producer, single consumer (SPSC) queue. It's easy to write a sync-free fixed size SPSC queue using a circular buffer*. Slightly trickier is a queue that grows as needed. You can use a linked list to represent the queue, but if you leave the nodes to be garbage collected once you're done with them, the GC will need to involve all the cores in collecting the finished nodes. Instead, I've implemented a proof of concept inspired by this intel article which reuses the nodes by putting them in a second queue to send back to the producer. * In all these cases, you need to use memory barriers correctly, but these are local to a core, so don't have the same scalability problems as atomic memory operations. Performance tests I tried benchmarking my SPSC queue against the .NET ConcurrentQueue, and against a standard Queue protected by locks. In some ways, this isn't a fair comparison, because both of these support multiple producers and multiple consumers, but I'll come to that later. I started on my dual-core laptop, running a simple test that had one thread producing 64 bit integers, and another consuming them, to measure the pure overhead of the queue. So, nothing very interesting here. Both concurrent collections perform better than the lock-based one as expected, but there's not a lot to choose between the ConcurrentQueue and my SPSC queue. I was a little disappointed, but then, the .NET Framework team spent a lot longer optimising it than I did. So I dug out a more powerful machine that Red Gate's DBA tools team had been using for testing. It is a 6 core Intel i7 machine with hyperthreading, adding up to 12 logical cores. Now the results get more interesting. As I increased the number of producer-consumer pairs to 6 (to saturate all 12 logical cores), the locking approach was slow, and got even slower, as you'd expect. What I didn't expect to be so clear was the drop-off in performance of the lock-free ConcurrentQueue. I could see the machine only using about 20% of available CPU cycles when it should have been saturated. My interpretation is that as all the cores used atomic memory operations to safely access the queue, they ended up spending most of the time notifying each other about cache lines that need invalidating. The sync-free approach scaled perfectly, despite still working via shared memory, which after all, should still be a bottleneck. I can't quite believe that the results are so clear, so if you can think of any other effects that might cause them, please comment! Obviously, this benchmark isn't realistic because we're only measuring the overhead of the queue. Any real workload, even on a machine with 12 cores, would dwarf the overhead, and there'd be no point worrying about this effect. But would that be true on a machine with 100 cores? Still to be solved. The trouble is, you can't build many concurrent algorithms using only an SPSC queue to communicate. In particular, I can't see a way to build something as general purpose as actors on top of just SPSC queues. Fundamentally, an actor needs to be able to receive messages from multiple other actors, which seems to need an MPSC queue. I've been thinking about ways to build a sync-free MPSC queue out of multiple SPSC queues and some kind of sign-up mechanism. Hopefully I'll have something to tell you about soon, but leave a comment if you have any ideas.

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  • Exadata a kiskereskedelem (retail) számára

    - by Fekete Zoltán
    Egyik kedvenc blogomban a Rittman Mead honlapján hasznos eloadásra jelent meg infó és letöltési lehetoség. (Lásd a jobb oldali Top Tags dobozban a "blog" kulcsszót, és a legalsó bejegyzést.) Az eloadás címe: Exadata in the Retail Sector, azaz Exadata a felhasználása a kiskereskedelemben. Ezt az eloadást Jon Mead tartotta 2010. március 23-án Londonban az Exadata V2, Oracle Extreme Performance Data Warehousing Seminar rendezvényen. Mint láthatjuk, szinte minden gyümölcsrol beszéltek az Oracle adattárház és üzleti intelligencia virágzó gyümölcsökertjébol az Oracle BI, 11gR2 adattárház tulajdonságai és más témákban. Az eloadások a következo területekrol szóltak: - Exadata techikai ismertetés - ügyfél sztorik: LGR, Allegro, és nagy-britannia egyik legnagyobb online elektronikai kiskereskedelmi cége - Oracle BI - GoldenGate (adatreplikáció) - advanced compression (tranzakciós adatok tömörítése) - particionálás - OLAP - adatbányászat, Oracle Data Mining

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  • Can find any /.ecryptfs dir to retrieve my encrypted home dir

    - by Roberto de Armas
    At firs sorry for my english, it isn't my native languaje. I've readed some questions similar but no the exactly whith the same problem. I've moved my home directory to a separated partitión (Ubuntu 11.10) following this tutorial http://www.ubuntu-es.org/node/58233 After checking that they were all my files and folders (forgetting that one of dirs was encrypted by ecryptfs) i've installed fedora 16. Well, suprised when in my home folder was an Readme.txt advising me that my folder was unmounted for security reasons and proposing to type in comand line "ecryptfs-mount-Private" (din't work) or make click on labeled icon "acces your private data desktop" (neither din't work). After three days reading all i could find on the internet, i follow The Dustin Kirkland tutorial in http://blog.dustinkirkland.com/2011/04/introducing-ecryptfs-recover-private.html, but any /.ecryptfs was found. I'm sure that the data are somewere (the size of the moved dir is identical to the original one). Any help would by greatly appreciated. Thaks a lot.

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  • Benefit of using Data URI to embed images within HTML document and its cross-browser compatibility

    - by Manoj Agarwal
    I want to embed an image using Data URI within HTML document so that we don't need image as a separate attachment, we get just one HTML file that contains the actual image. What are its advantages and disadvantages? Does IE10 supports it? Is it useful to have such an implementation? I am working on an application, where we have html documents that link towards images stored in some location. If I use tiny online editor, as images are saved somewhere in the server, while editing the document, i can provide a link towards that image, but can't preview the final document with images from within tiny editor. If I chose to download the file locally, then i will need to download the images from server side. It looks a bit overkill, so I thought if Data URI could be used in such a situation.

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  • Securely sending data from shared hosted PHP script to local MSSQL

    - by user329488
    I'm trying to add data from a webhook (from a web cart) to a local Microsoft SQL Server. It seems like the best route for me is to use a PHP script to listen for new data (POST as json), parse it, then query to add to MSSQL. I'm not familiar with security concerning the connection between the PHP script (which would sit on a shared-host website) and the local MSSQL database. I would just keep the PHP script running on the same localhost (have Apache running on Windows), but the URI for the webhook needs to be publicly accessible. Alternately, I assume that I could just schedule a script from the localhost to check periodically for updates through the web carts API, though the webhooks seem to be more fool-proof for an amateur programmer like myself. What steps can I take to ensure security when using a PHP on a remote, shared-host to connect to MSSQL on my local machine?

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  • Sorting and Paging a Grid of Data in ASP.NET MVC

    This article is the fifth installment in an ongoing series on displaying a grid of data in an ASP.NET MVC application. Previous articles in this series examined how to sort, page, and filter a grid of data, but none have looked at combining one or more of these features in a single grid. This article and the next one show how to merge these features into a single grid. In particular, this article looks at displaying a grid that can handle both sorting and paging. The subsequent article will examine combining sorting, paging and filtering. Like with its predecessors, this article offers step-by-step instructions and includes a complete, working demo available for download at the end of the article. Read on to learn more! Read More >

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  • How do I handle 3rd party search result data (via cache)

    - by reikyoushin
    I have a search function on my site and it is taking data from 6 different 3rd party resources. The problem is, it takes too long requesting the data over and over again on the results page. I've read for questions like this on SO about session not being a good choice but for me 'memcache' is not an option, because the server doesn't have memcached installed and I have no way to install it now. Is there any other approach to do this? Storing in the database seem inappropriate because the data depends on the search terms requested. What I've been thinking is writing a file on the server that would act as a cache for this file but I don't know how I would know when to delete it after.

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  • Rails noob - How to work on data stored in models

    - by Raghav Kanwal
    I'm a beginner to Ruby and Rails, and I have made a couple applications like a Microposts clone and a Todo-List for starters, but I'm starting work on another project. I've got 2 models - user and tracker, you log in via the username which is authenticated and you can log down data which is stored in the tracker table. The tracker has a column named "Calories" and I would like Rails to sum all of the values entered if they are on the same date, and output the result which is subtracted from, say 3000 in a new statement after the display of the model. I know what I'm talking about is just ruby code, im just not sure how to incorporate it. :( Could someone please guide me through this? And also link me to some guides/tutorials which teach working on data from models? Thank you :)

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