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  • Is there a RAR extractor (for multiple rar files like .r00 etc.) that will use all of my quad cores?

    - by Christopher Done
    I've got a quad core Intel processor. I've got a big file split into little ones as RAR files, foo.r00, foo.r01, etc. which the RAR program extracts into one file/directory. Is there a RAR program that I can specify like "use four cores" in the extract process? At the moment it sits there using 100% of one core. I recognise the bottleneck might be my hard drive anyway, but I don't see a lot of HD usage and suspect the decompression process is more intensive than waiting on I/O. For example, GNU Make accepts a (-j, I think) argument to tell it how many cores to use, which I used to compile PHP 6 really quickly.

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  • How do I get rid of com.apple.launchd.peruser errors in my log?

    - by Chris R
    I'm getting repeated errors in my console log that look (basically) like this: 10-09-29 10:06:08 AM com.apple.launchd[1] (com.apple.launchd.peruser.501[51581]) getpwuid("501") failed 10-09-29 10:06:08 AM com.apple.launchd[1] (com.apple.launchd.peruser.501[51581]) Exited with exit code: 1 This machine was set up using the migration assistant, from a machine where my UID was 501, but here it's 505. I have the same username and group set, of course, but... So, where is this peruser launchd tool configured, so that I can disable the daemons that are causing this error message?

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  • Limit user to one CPU core in windows 7

    - by Dean Ward
    I let my family members use my pc over rdp to play their flash-based games as their laptops overheat if they use them directly. I have it setup so I can use the pc at the same time as them. The pc has a quad core cpu and I would like to be able to assign one of those cores to the user logged in via RDP so that the other 3 cores are left alone. Is this possible? They login via a specific user account setup for the purpose. Thanks for any advice!

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  • How do I get rid of com.apple.launchd.peruser errors in my log?

    - by Chris R
    I'm getting repeated errors in my console log that look (basically) like this: 10-09-29 10:06:08 AM com.apple.launchd[1] (com.apple.launchd.peruser.501[51581]) getpwuid("501") failed 10-09-29 10:06:08 AM com.apple.launchd[1] (com.apple.launchd.peruser.501[51581]) Exited with exit code: 1 This machine was set up using the migration assistant, from a machine where my UID was 501, but here it's 505. I have the same username and group set, of course, but... So, where is this peruser launchd tool configured, so that I can disable the daemons that are causing this error message?

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  • win 2008 core create a partition with an offset to allow other partition expand

    - by Rqomey
    We are running a win 2008 core host in a HyperV role. We have expanded the logical drive on a RAID 1+0 array belonging to the server, as we needed more space. We have two data partitions D: and E: I want to expand them both so they use all space, and are equally sized. There is data on all partitions, although E is not in live use (so files can be moved and copied from it. Current: What I want- temporary Partition (F:) at end of drive: I am going to create a temporary partition F: so I can move the files from E: onto it, then delete E:, expand D: to the desired size, then rename F: to E: To do this I need to create F: from the end of the drive, ie. have unused space between E: and F: tl;dr How do I create a partition with a large offset in Windows server?

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  • What motherboard for a Core i7 920 Processor?

    - by jasondavis
    I am wanting to build a really nice PC, price is not to important as I will buy pieces every week or whatever it takes until I get everything I need. I am not a gamer but I would like to watch video and have 3-4 monitors. I do a lot of programming and use a lot of big programs so I would like to go all out and get a lot of Memory, probably at least 12gb but possibly more even as I see many boards support up to 24gb now. Will be using Windows 7. I have decided to go with the Core i7 920 Processor BX80601920. Based on what I posted above, can you please recommend some good motherboards I should look at ? Also some good places to purchase them online. Thanks for any help, tips, etc.

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  • Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder?

    - by Selin Peck
    Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder? I used to start office work by removing chrome User Data, replacing it with my own User Data copied from my external drive, saving the original User Data to other folder. Before leaving in the evening, I will take back my own User Data, and bring back the original User Data where it is originally saved. Is this process advisable? Would I be safe this way or if not, where else does chrome save data outside of User Data folder in AppData? Also, how is the process in Mozilla Firefox?

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  • recommendation for configuration for a multi-core guestOS

    - by reidLinden
    Hi there, I've just received an upgraded Host machine, and am looking to push some of those advances to my workstations Guest OS(s). In particular, I used to have a single processor, with 2 cores, so my guestOS only had 1/1. Now, I've got a single processor with 8 cores, so I'm curious about what would be recommended for my GuestOS now? 1 processor/4 cores? 2 processors/2Cores? 4 processors/1 core? My instinct says to stick with the number of physical processors (or less), but, is that based on reality? I spent a good while looking for an answer to this, but perhaps my google-karma isn't in my favor today. Suggestions?

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  • How do I populate multiple records of data into a PDF form like a mail-merge?

    - by user38801
    I have Acrobat Pro, and I have a PDF with a form on it. Assuming the fields in the form correspond to a data source (like rows in an RDBMS table or xml file), I want to then print multiple copies of the PDF file, with each copy having the values of a different row in the data source. It is preferable to directly interface with an actual database, rather than having to save an XML file every time I do this. If this involves programming that's cool too, I only posted here because the question didn't seem appropriate for StackOverflow. Thanks!

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  • Multiple SQL Standard Instances on 4 Processor/32-core Server

    - by Theowood
    We have a large 4 processor/32-core server with 192GB of memory available in the data center and over twenty small SQL Standard databases to consolidate. They are a mix of SQL 2012 and 2008 R2 for 3rd-party apps. Is there any issue with simply installing two instances of SQL Standard on the server - one for 2012 and one for 2008 R2 ? Each instance will use up to 64GB out of the 192GB and 16 cores. If we did this with Enterprise, the licensing would be a fortune and the Enterprise features are not needed.

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  • Remotely Managing Storage on Hyper-V 2012 Core

    - by Vazgen
    I have a core Hyper-V Server 2012 that I am remotely managing from a Windows 8 client. I can connect in Hyper-V Manager, Server Manager, and MMC. However, I don't understand how I can manage the physical hard drive (for ex, deleting vhdx files, creating folders, etc) from my Windows 8 client. I tried to attach the remote share as follows: q: \\MyServer\c$ It said command completed successfully, but I don't see the drive on my client's Explorer. I can get to it in cmd.exe on the client but how can I manage it in a GUI? explorer q: Throws error:

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  • Ways to improve completeness of files for data recovery and scanning?

    - by SteveO
    I am using R-studio for data recovery on one of my ntfs partition. There is a pdf file about 16MB, but the software can only recover 15MB of it. So I am thinking about what ways can be used to improve the quality of scanning and recovery by the software? I am looking around its preferences. I am not quite sure whether there are some adjustable parameters for scanning and recovery which can be fine-tuned to improve the quality? R-studio has a free demo version, for which scanning is free,but recovery isn't. It is downloadable from http://www.data-recovery-software.net/Data_Recovery_Download.shtml Its manual is here http://www.r-tt.com/downloads/Recovery_Manual.pdf. I have tried my best to search for answers in the manual, but failed to find one. Their technical support is not as good as their software, and helpless usually in my opinion. Thanks!

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  • apache tomcat sermyadmin deployment error

    - by lepricon123
    I am getting the following errro when i try to start the application Mar 23, 2010 7:51:09 PM org.apache.catalina.core.ApplicationContext log INFO: Set web app root system property: 'sermyadmin-production-2.0.1' = [/usr/local/tomcat6/webapps/sermyadmin/] Mar 23, 2010 7:51:09 PM org.apache.catalina.core.ApplicationContext log INFO: Initializing log4j from [/usr/local/tomcat6/webapps/sermyadmin/WEB-INF/classes/log4j.properties] Mar 23, 2010 7:51:09 PM org.apache.catalina.core.ApplicationContext log INFO: Initializing Spring root WebApplicationContext Mar 23, 2010 7:51:23 PM org.apache.catalina.core.StandardContext listenerStart SEVERE: Exception sending context initialized event to listener instance of class org.codehaus.groovy.grails.web.context.GrailsContextLoaderListener org.springframework.beans.factory.access.BootstrapException: Error executing bootstraps; nested exception is org.codehaus.groovy.runtime.InvokerInvocationException: org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute query; nested exception is org.hibernate.exception.SQLGrammarException: could not execute query at org.codehaus.groovy.grails.web.context.GrailsContextLoader.createWebApplicationContext(GrailsContextLoader.java:66) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3843) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4350) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525) at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:829) at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:718) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:490) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1147) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053) at org.apache.catalina.core.StandardHost.start(StandardHost.java:719) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:578) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413) Caused by: org.codehaus.groovy.runtime.InvokerInvocationException: org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute query; nested exception is org.hibernate.exception.SQLGrammarException: could not execute query at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3843) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4350) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525) at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:829) at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:718) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:490) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1147) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053) at org.apache.catalina.core.StandardHost.start(StandardHost.java:719) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:578) ... 2 more Caused by: org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute query; nested exception is org.hibernate.exception.SQLGrammarException: could not execute query at BootStrap$_closure1.doCall(BootStrap.groovy:7) ... 20 more Caused by: org.hibernate.exception.SQLGrammarException: could not execute query ... 21 more Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'opensips.jsec_role' doesn't exist at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)

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  • Django data migration when changing a field to ManyToMany

    - by Ken H
    I have a Django application in which I want to change a field from a ForeignKey to a ManyToManyField. I want to preserve my old data. What is the simplest/best process to follow for this? If it matters, I use sqlite3 as my database back-end. If my summary of the problem isn't clear, here is an example. Say I have two models: class Author(models.Model): author = models.CharField(max_length=100) class Book(models.Model): author = models.ForeignKey(Author) title = models.CharField(max_length=100) Say I have a lot of data in my database. Now, I want to change the Book model as follows: class Book(models.Model): author = models.ManyToManyField(Author) title = models.CharField(max_length=100) I don't want to "lose" all my prior data. What is the best/simplest way to accomplish this? Ken

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  • SVN problems after migration with CVS2SVN

    - by Bjorn C
    We´ve migrated from CVS on AIX to SVN on Linux via CVS2SVN. The migration seems to have went well but when working in SVN we get a lot of Tree Conflicts that doesn´t seem to be conflicts at all? Looking at the revision graphs, one can see that the graph for e.g. trunk and a branch isn´t the same, i.e. they contain different sets of revisions of the file. Either of the 3 ways to resolve this conflict when merging in TortoiseSVN leaves the revision graphs separate, they cannot be "melted" together. Could it be that CVS2SVN didn´t understand that a file in different branches is the same even if the file system path is the same? Anyone who has experienced this? Thanks, Bjorn

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  • rails g migration error

    - by user1506183
    I don't know what to do. Try to use command $ rails g migration vacancy but this command give me error: invoke active_record /home/proger/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:203:in `parse': (<unknown>): mapping values are not allowed in this context at line 21 column 11 (Psych::SyntaxError) from /home/proger/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:203:in `parse_stream' from /home/proger/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:151:in `parse' ... There are many rows in error code I don't know how to fix that Thanks

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  • Class library modification / migration

    - by Clint
    I have 3 class libraries. A BBL, a DAL, and a DATA (about 15 datasets). Currently 4 [major] applications utilize the functionality in these DLL's. I'm rewriting one of those applications and I need to (1) Use some of the existing functionality in the libraries (2) Change some of it (3) Add new functionality (4) Add new datasets. I'm back and forth about the best way to do this, while keeping my risks at a minimum. Some thoughts.. 1) Use the existing projects and don't make any modifications, only additions 2) Make new libraries, bring over the code I can use, and make additions as needed 3) Implement partial classes in the existing projects Eventually all 4 applications will use the newest functionality, but it will be a slow migration; so the old code can't be depricated yet. Any thoughts?

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  • Using Microsoft's Chart Controls In An ASP.NET Application: Serializing Chart Data

    In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the Getting Started article rendered a column chart with seven columns whose labels and values were defined statically in the <asp:Series> tag's <Points> collection. Given this functionality, it should come as no surprise that the Microsoft Chart Controls also support serialization. Serialization is the process of persisting the state of a control or an object to some other medium, such as to disk. Deserialization is the inverse process, and involves taking the persisted data and recreating the control or object. With just a few lines of code you can persist the appearance settings, the data, or both to a file on disk or to any stream. Likewise, it takes just a few lines of codes to reconstitute a chart from the persisted information. This article shows how to use the Microsoft Chart Control's serialization functionality by examining a demo application that allows users to create custom charts, specifying the data to plot and some appearance-related settings. The user can then save a "snapshot" of this chart, which persists its appearance and data to a record in a database. From another page, users can view these saved chart snapshots. Read on to learn more! Read More >

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  • Join our webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate

    - by Irem Radzik
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";} Data integration team has organized a series of webcasts for this summer. We are kicking it off this Thursday June 30th at 10am PT with a product update webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate. In this webcast you will hear from product management about the new patch updates to both GoldenGate 11g R1 and ODI 11gR1. Jeff Pollock, Sr. Director of Product Management for ODI will talk about the new features in Oracle Data Integrator 11.1.1.5, including the data lineage integration with OBI EE, enhanced web services to support flexible architectures as well as capabilities for efficient object execution such as Load Plans. Jeff will discuss support for complex files and performance enhancements. Chris McAllister, Sr. Director of Product Management for Oracle GoldenGate will cover the new features of Oracle GoldenGate 11.1.1.1 such as increased data security by supporting Oracle Database Advanced Security option, deeper integration with Oracle Database, and the expanded list of heterogeneous databases GoldenGate supports . Chris will also talk about the new Oracle GoldenGate 11gR1 release for HP NonStop platform and will provide information on our strategic direction for product development. Join us this Thursday at 10am PT/ 1pm ET to hear directly from Data Integration Product Management . You can register here for the June 30th webcast as well as for the upcoming ones in our summer webcast series.

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  • Oracle Database Security Protecting the Oracle IRM Schema

    - by Simon Thorpe
    Acquiring the Information Rights Management technology in 2006 was part of Oracle's strategic security vision and IRM compliments nicely the overall Oracle security set of solutions. A year ago I spoke about how Oracle has solutions that can help companies protect information throughout its entire life cycle. With our acquisition of Sun this set of solutions has solidified and has even extended down to the operating system and hardware level. Oracle can now offer customers technology that protects their data from the disk, through the database to documents on the desktop! With the recent release of Oracle IRM 11g I was tasked to configure demonstration and evaluation environments and I thought it would make a nice story to leverage some of the security features in the latest release of the Oracle Database. After building these environments I thought I would put together a simple video demonstrating how both Database Advanced Security and Information Rights Management combined can provide a very secure platform for protecting your information. Have a look at the following which highlights these database security options.Transparent Data Encryption protecting the communication from the Oracle IRM server to the Database server. Encryption techniques provide confidentiality and integrity of the data passing to and from the IRM service on the back end. Transparent Data Encryption protecting the Oracle IRM database schema. Encryption is used to provide confidentiality of the IRM data whilst it resides at rest in the database table space. Database Vault is used to ensure only the Oracle IRM service has access to query and update the information that resides in the database. This is an excellent method of ensuring that database administrators cannot look at or make changes to the Oracle IRM database whilst retaining their ability to administrate the database. The last thing you want after deploying an IRM solution is for a curious or unhappy DBA to run a query that grants them rights to your company financial data or documents pertaining to a merger or acquisition.

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  • SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

    - by pinaldave
    This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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  • Announcing Sesame Data Browser

    - by Fabrice Marguerie
    At the occasion of MIX10, which is currently taking place in Las Vegas, I'd like to announce Sesame Data Browser.Sesame will be a suite of tools for dealing with data, and Sesame Data Browser will be the first tool from that suite.Today, during the second MIX10 keynote, Microsoft demonstrated how they are pushing hard to get OData adopted. If you don't know about OData, you can visit the just revamped dedicated website: http://odata.org. There you'll find about the OData protocol, which allows you to publish and consume data on the web, the OData SDK (with client libraries for .NET, Java, Javascript, PHP, iPhone, and more), a list of OData producers, and a list of OData consumers.This is where Sesame Data Browser comes into play. It's one of the tools you can use today to consume OData.I'll let you have a look, but be aware that this is just a preview and many additional features are coming soon.Sesame Data Browser is part of a bigger picture than just OData that will take shape over the coming months. Sesame is a project I've been working on for many months now, so what you see now is just a start :-)I hope you'll enjoy what you see. Let me know what you think.

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  • Methodology behind fetching large XML data sets in pieces

    - by Jerry Dodge
    I am working on an HTTP Server in Delphi which simply sends back a custom XML dataset. I am not following any type of standard formatting, such as SOAP. I have the system working seamlessly, except one small flaw: When I have a very large dataset to send back to the client, it might take up to 2 minutes for all the data to be transferred. The HTTP Server I'm building is essentially an XML Data based API around a database, implementing the common business rule - therefore, the requests are specific to the data behind the system. When, for example, I fetch a large set of product data, I would like to break this down and send it back piece by piece. However, a single HTTP request calls for a single response. I can't necessarily keep feeding the client with multiple different XML packets unless the client explicitly requests it. I don't have any session management, but rather an API Key. I know if I had sessions, I could keep-alive a dataset temporarily for a client, and they could request bits and pieces of it. However, without session management, I would have to execute the SQL query multiple times (for each chunk of data), and in the mean-time, if that data changes, the "pages" might get messed up, therefore causing items to show on the wrong pages, after navigating to a different page. So how is this commonly handled? What's the methodology behind breaking down a large XML dataset into chunks to save the load?

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  • Using Microsoft's Chart Controls In An ASP.NET Application: Serializing Chart Data

    In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the Getting Started article rendered a column chart with seven columns whose labels and values were defined statically in the <asp:Series> tag's <Points> collection. Given this functionality, it should come as no surprise that the Microsoft Chart Controls also support serialization. Serialization is the process of persisting the state of a control or an object to some other medium, such as to disk. Deserialization is the inverse process, and involves taking the persisted data and recreating the control or object. With just a few lines of code you can persist the appearance settings, the data, or both to a file on disk or to any stream. Likewise, it takes just a few lines of codes to reconstitute a chart from the persisted information. This article shows how to use the Microsoft Chart Control's serialization functionality by examining a demo application that allows users to create custom charts, specifying the data to plot and some appearance-related settings. The user can then save a "snapshot" of this chart, which persists its appearance and data to a record in a database. From another page, users can view these saved chart snapshots. Read on to learn more! Read More >

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