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  • Criteria for a programming language to be considered "mature"

    - by Giorgio
    I was recently reading an answer to this question, and I was struck by the statement "The language is mature". So I was wondering what we actually mean when we say that "A programming language is mature"? Normally, a programming language is initially developed out of a need, e.g. Try out / implement a new programming paradigm or a new combination of features that cannot be found in existing languages. Try to solve a problem or overcome a limitation of an existing language. Create a language for teaching programming. Create a language that solves a particular class of problems (e.g. concurrency). Create a language and an API for a special application field, e.g. the web (in this case the language might reuse a well-known paradigm, but the whole API must be new). Create a language to push your competitor out of the market (in this case the creator might want the new language to be very similar to an existing one, in order to attract developers to the new programming language and platform). Regardless of what the original motivation and scenario in which a language has been created, eventually some languages are considered mature. In my intuition, this means that the language has achieved (at least one of) its goals, e.g. "We can now use language X as a reliable tool for writing web applications." This is however a bit vague, so I wanted to ask what you consider the most important criteria (if any) that are applied when saying that a language is mature. IMPORTANT NOTE This question is (on purpose) language-agnostic because I am only interested in general criteria. Please write only language-agnostic answers and comments! I am not asking whether any specific "language X is mature" or "which programming languages can be considered mature", or whether "language X is more mature than language Y": please avoid posting any opinions or reference about any specific languages because these are out of the scope of this question. EDIT To make the question more precise, by criteria I mean such things as "tool support", "adoption by the industry", "stability", "rich API", "large user community", "successful application record", "standardization", "clean and uniform semantics", and so on.

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  • How steep is the learning curve when moving from shared (cPanel) webhosting to a VPS (e.g. Linode)?

    - by pax
    In all shared hosting environments, one can be agnostic to the running OS. What happens in the case of Linode? I know it allows pretty flexible Linux installations, but for starters, besides choosing a distro, does one need to do more Linux sysadmin stuff besides the basic web hosting (DNS management, MySql database creations, users ftp/ssh access/ backups)? Does Linode have a module that would cover cPanel's basic features? Does one need to install/start/upgrade each aspect of LAMP (software bundle)?

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  • Free eBook: SQL Server Hardware

    SQL Server Hardware will provide the fundamental knowledge and resources you need to make intelligent decisions about choice, and optimal installation and configuration, of SQL Server hardware, operating system and the SQL Server RDBMS. New! SQL Prompt 6 – now with tab historyWriting, exploring, and editing SQL just became even more effortless with SQL Prompt 6. Download a free trial.

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  • How to Detect and Fix Table Corruption in Oracle?

    Oracle is an RDBMS (Relational Database Management System), developed and marketed by Oracle Corporation. It has a major presence in database computing. It stores all your valuable data in the DBF fi... [Author: Mark Willium - Computers and Internet - May 13, 2010]

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  • Stairway to SQL Dialects Level 3: MySQL

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

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  • ??2???????·???·???????????????|Oracle Coherence|??????

    - by ???02
    ?????·???·??????????????????·???·???????????????????????????????????????????Oracle Coherence???????????????????????????????????????????????????????2???????put/get??????????·??????????????? RDBMS?????????·???????????????????????????????·???·???????????????????????????????????????(???3????????????????????????????????)????Coherence???????3????????????????????????????????????????????????????????????????????????3:???????// ????????100????????????Filter filter = new EqualsFilter("getProductId", 100);// ????????????Set orders = orderCache.entrySet(filter); ????·??????????????·???????????????????????????????????????????????????????????????????????????????????Java??????????Java?????·??????????????????????????????????(???4)???????????????????(???5)??????Coherence???????·??????????????MapEvent????????????????????????????????????????????????????4:???·???????// ????????????????????·???public class ProcessOrderListener implements MapListener {public void entryInserted(MapEvent event) { /* ????? */ }public void entryUpdated(MapEvent event) {}public void entryDeleted(MapEvent event) {}}???5:????????orderCache.addMapListener(new ProcessOrderListener()); ????????????????????????????????(????)????????????????????????????????????????????100??????????0.1???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·????????????????????????????????????????????????????????????????????Coherence????????????????????????????(???????)???????????·??????????Invocation?????????????(?4)?????????????????????????????????????????????????????????????????????????·?????????????????????????????????????????????????????????·????????????????????????????????????????????????????????????Coherence??????????????????????????????????????????????????????????????????????????????????????????????????????????·???·???????????·?????????????·????????????????123

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  • SQL SERVER – Import CSV into Database – Transferring File Content into a Database Table using CSVexpress

    - by pinaldave
    One of the most common data integration tasks I run into is a desire to move data from a file into a database table.  Generally the user is familiar with his data, the structure of the file, and the database table, but is unfamiliar with data integration tools and therefore views this task as something that is difficult.  What these users really need is a point and click approach that minimizes the learning curve for the data integration tool.  This is what CSVexpress (www.CSVexpress.com) is all about!  It is based on expressor Studio, a data integration tool I’ve been reviewing over the last several months. With CSVexpress, moving data between data sources can be as simple as providing the database connection details, describing the structure of the incoming and outgoing data and then connecting two pre-programmed operators.   There’s no need to learn the intricacies of the data integration tool or to write code.  Let’s look at an example. Suppose I have a comma separated value data file with data similar to the following, which is a listing of terminated employees that includes their hiring and termination date, department, job description, and final salary. EMP_ID,STRT_DATE,END_DATE,JOB_ID,DEPT_ID,SALARY 102,13-JAN-93,24-JUL-98 17:00,Programmer,60,"$85,000" 101,21-SEP-89,27-OCT-93 17:00,Account Representative,110,"$65,000" 103,28-OCT-93,15-MAR-97 17:00,Account Manager,110,"$75,000" 304,17-FEB-96,19-DEC-99 17:00,Marketing,20,"$45,000" 333,24-MAR-98,31-DEC-99 17:00,Data Entry Clerk,50,"$35,000" 100,17-SEP-87,17-JUN-93 17:00,Administrative Assistant,90,"$40,000" 334,24-MAR-98,31-DEC-98 17:00,Sales Representative,80,"$40,000" 400,01-JAN-99,31-DEC-99 17:00,Sales Manager,80,"$55,000" Notice the concise format used for the date values, the fact that the termination date includes both date and time information, and that the salary is clearly identified as money by the dollar sign and digit grouping.  In moving this data to a database table I want to express the dates using a format that includes the century since it’s obvious that this listing could include employees who left the company in both the 20th and 21st centuries, and I want the salary to be stored as a decimal value without the currency symbol and grouping character.  Most data integration tools would require coding within a transformation operation to effect these changes, but not expressor Studio.  Directives for these modifications are included in the description of the incoming data. Besides starting the expressor Studio tool and opening a project, the first step is to create connection artifacts, which describe to expressor where data is stored.  For this example, two connection artifacts are required: a file connection, which encapsulates the file system location of my file; and a database connection, which encapsulates the database connection information.  With expressor Studio, I use wizards to create these artifacts. First click New Connection > File Connection in the Home tab of expressor Studio’s ribbon bar, which starts the File Connection wizard.  In the first window, I enter the path to the directory that contains the input file.  Note that the file connection artifact only specifies the file system location, not the name of the file. Then I click Next and enter a meaningful name for this connection artifact; clicking Finish closes the wizard and saves the artifact. To create the Database Connection artifact, I must know the location of, or instance name, of the target database and have the credentials of an account with sufficient privileges to write to the target table.  To use expressor Studio’s features to the fullest, this account should also have the authority to create a table. I click the New Connection > Database Connection in the Home tab of expressor Studio’s ribbon bar, which starts the Database Connection wizard.  expressor Studio includes high-performance drivers for many relational database management systems, so I can simply make a selection from the “Supplied database drivers” drop down control.  If my desired RDBMS isn’t listed, I can optionally use an existing ODBC DSN by selecting the “Existing DSN” radio button. In the following window, I enter the connection details.  With Microsoft SQL Server, I may choose to use Windows Authentication rather than rather than account credentials.  After clicking Next, I enter a meaningful name for this connection artifact and clicking Finish closes the wizard and saves the artifact. Now I create a schema artifact, which describes the structure of the file data.  When expressor reads a file, all data fields are typed as strings.  In some use cases this may be exactly what is needed and there is no need to edit the schema artifact.  But in this example, editing the schema artifact will be used to specify how the data should be transformed; that is, reformat the dates to include century designations, change the employee and job ID’s to integers, and convert the salary to a decimal value. Again a wizard is used to create the schema artifact.  I click New Schema > Delimited Schema in the Home tab of expressor Studio’s ribbon bar, which starts the Database Connection wizard.  In the first window, I click Get Data from File, which then displays a listing of the file connections in the project.  When I click on the file connection I previously created, a browse window opens to this file system location; I then select the file and click Open, which imports 10 lines from the file into the wizard. I now view the file’s content and confirm that the appropriate delimiter characters are selected in the “Field Delimiter” and “Record Delimiter” drop down controls; then I click Next. Since the input file includes a header row, I can easily indicate that fields in the file should be identified through the corresponding header value by clicking “Set All Names from Selected Row. “ Alternatively, I could enter a different identifier into the Field Details > Name text box.  I click Next and enter a meaningful name for this schema artifact; clicking Finish closes the wizard and saves the artifact. Now I open the schema artifact in the schema editor.  When I first view the schema’s content, I note that the types of all attributes in the Semantic Type (the right-hand panel) are strings and that the attribute names are the same as the field names in the data file.  To change an attribute’s name and type, I highlight the attribute and click Edit in the Attributes grouping on the Schema > Edit tab of the editor’s ribbon bar.  This opens the Edit Attribute window; I can change the attribute name and select the desired type from the “Data type” drop down control.  In this example, I change the name of each attribute to the name of the corresponding database table column (EmployeeID, StartingDate, TerminationDate, JobDescription, DepartmentID, and FinalSalary).  Then for the EmployeeID and DepartmentID attributes, I select Integer as the data type, for the StartingDate and TerminationDate attributes, I select Datetime as the data type, and for the FinalSalary attribute, I select the Decimal type. But I can do much more in the schema editor.  For the datetime attributes, I can set a constraint that ensures that the data adheres to some predetermined specifications; a starting date must be later than January 1, 1980 (the date on which the company began operations) and a termination date must be earlier than 11:59 PM on December 31, 1999.  I simply select the appropriate constraint and enter the value (1980-01-01 00:00 as the starting date and 1999-12-31 11:59 as the termination date). As a last step in setting up these datetime conversions, I edit the mapping, describing the format of each datetime type in the source file. I highlight the mapping line for the StartingDate attribute and click Edit Mapping in the Mappings grouping on the Schema > Edit tab of the editor’s ribbon bar.  This opens the Edit Mapping window in which I either enter, or select, a format that describes how the datetime values are represented in the file.  Note the use of Y01 as the syntax for the year.  This syntax is the indicator to expressor Studio to derive the century by setting any year later than 01 to the 20th century and any year before 01 to the 21st century.  As each datetime value is read from the file, the year values are transformed into century and year values. For the TerminationDate attribute, my format also indicates that the datetime value includes hours and minutes. And now to the Salary attribute. I open its mapping and in the Edit Mapping window select the Currency tab and the “Use currency” check box.  This indicates that the file data will include the dollar sign (or in Europe the Pound or Euro sign), which should be removed. And on the Grouping tab, I select the “Use grouping” checkbox and enter 3 into the “Group size” text box, a comma into the “Grouping character” text box, and a decimal point into the “Decimal separator” character text box. These entries allow the string to be properly converted into a decimal value. By making these entries into the schema that describes my input file, I’ve specified how I want the data transformed prior to writing to the database table and completely removed the requirement for coding within the data integration application itself. Assembling the data integration application is simple.  Onto the canvas I drag the Read File and Write Table operators, connecting the output of the Read File operator to the input of the Write Table operator. Next, I select the Read File operator and its Properties panel opens on the right-hand side of expressor Studio.  For each property, I can select an appropriate entry from the corresponding drop down control.  Clicking on the button to the right of the “File name” text box opens the file system location specified in the file connection artifact, allowing me to select the appropriate input file.  I indicate also that the first row in the file, the header row, should be skipped, and that any record that fails one of the datetime constraints should be skipped. I then select the Write Table operator and in its Properties panel specify the database connection, normal for the “Mode,” and the “Truncate” and “Create Missing Table” options.  If my target table does not yet exist, expressor will create the table using the information encapsulated in the schema artifact assigned to the operator. The last task needed to complete the application is to create the schema artifact used by the Write Table operator.  This is extremely easy as another wizard is capable of using the schema artifact assigned to the Read Table operator to create a schema artifact for the Write Table operator.  In the Write Table Properties panel, I click the drop down control to the right of the “Schema” property and select “New Table Schema from Upstream Output…” from the drop down menu. The wizard first displays the table description and in its second screen asks me to select the database connection artifact that specifies the RDBMS in which the target table will exist.  The wizard then connects to the RDBMS and retrieves a list of database schemas from which I make a selection.  The fourth screen gives me the opportunity to fine tune the table’s description.  In this example, I set the width of the JobDescription column to a maximum of 40 characters and select money as the type of the LastSalary column.  I also provide the name for the table. This completes development of the application.  The entire application was created through the use of wizards and the required data transformations specified through simple constraints and specifications rather than through coding.  To develop this application, I only needed a basic understanding of expressor Studio, a level of expertise that can be gained by working through a few introductory tutorials.  expressor Studio is as close to a point and click data integration tool as one could want and I urge you to try this product if you have a need to move data between files or from files to database tables. Check out CSVexpress in more detail.  It offers a few basic video tutorials and a preview of expressor Studio 3.5, which will support the reading and writing of data into Salesforce.com. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • career in Mobile sw/Application Development [closed]

    - by pramod
    i m planning to do a course on Wireless & mobile computing.The syllabus are given below.Please check & let me know whether its worth to do.How is the job prospects after that.I m a fresher & from electronic Engg.The modules are- *Wireless and Mobile Computing (WiMC) – Modules* C, C++ Programming and Data Structures 100 Hours C Revision C, C++ programming tools on linux(Vi editor, gdb etc.) OOP concepts Programming constructs Functions Access Specifiers Classes and Objects Overloading Inheritance Polymorphism Templates Data Structures in C++ Arrays, stacks, Queues, Linked Lists( Singly, Doubly, Circular) Trees, Threaded trees, AVL Trees Graphs, Sorting (bubble, Quick, Heap , Merge) System Development Methodology 18 Hours Software life cycle and various life cycle models Project Management Software: A Process Various Phases in s/w Development Risk Analysis and Management Software Quality Assurance Introduction to Coding Standards Software Project Management Testing Strategies and Tactics Project Management and Introduction to Risk Management Java Programming 110 Hours Data Types, Operators and Language Constructs Classes and Objects, Inner Classes and Inheritance Inheritance Interface and Package Exceptions Threads Java.lang Java.util Java.awt Java.io Java.applet Java.swing XML, XSL, DTD Java n/w programming Introduction to servlet Mobile and Wireless Technologies 30 Hours Basics of Wireless Technologies Cellular Communication: Single cell systems, multi-cell systems, frequency reuse, analog cellular systems, digital cellular systems GSM standard: Mobile Station, BTS, BSC, MSC, SMS sever, call processing and protocols CDMA standard: spread spectrum technologies, 2.5G and 3G Systems: HSCSD, GPRS, W-CDMA/UMTS,3GPP and international roaming, Multimedia services CDMA based cellular mobile communication systems Wireless Personal Area Networks: Bluetooth, IEEE 802.11a/b/g standards Mobile Handset Device Interfacing: Data Cables, IrDA, Bluetooth, Touch- Screen Interfacing Wireless Security, Telemetry Java Wireless Programming and Applications Development(J2ME) 100 Hours J2ME Architecture The CLDC and the KVM Tools and Development Process Classification of CLDC Target Devices CLDC Collections API CLDC Streams Model MIDlets MIDlet Lifecycle MIDP Programming MIDP Event Architecture High-Level Event Handling Low-Level Event Handling The CLDC Streams Model The CLDC Networking Package The MIDP Implementation Introduction to WAP, WML Script and XHTML Introduction to Multimedia Messaging Services (MMS) Symbian Programming 60 Hours Symbian OS basics Symbian OS services Symbian OS organization GUI approaches ROM building Debugging Hardware abstraction Base porting Symbian OS reference design porting File systems Overview of Symbian OS Development – DevKits, CustKits and SDKs CodeWarrior Tool Application & UI Development Client Server Framework ECOM STDLIB in Symbian iPhone Programming 80 Hours Introducing iPhone core specifications Understanding iPhone input and output Designing web pages for the iPhone Capturing iPhone events Introducing the webkit CSS transforms transitions and animations Using iUI for web apps Using Canvas for web apps Building web apps with Dashcode Writing Dashcode programs Debugging iPhone web pages SDK programming for web developers An introduction to object-oriented programming Introducing the iPhone OS Using Xcode and Interface builder Programming with the SDK Toolkit OS Concepts & Linux Programming 60 Hours Operating System Concepts What is an OS? Processes Scheduling & Synchronization Memory management Virtual Memory and Paging Linux Architecture Programming in Linux Linux Shell Programming Writing Device Drivers Configuring and Building GNU Cross-tool chain Configuring and Compiling Linux Virtual File System Porting Linux on Target Hardware WinCE.NET and Database Technology 80 Hours Execution Process in .NET Environment Language Interoperability Assemblies Need of C# Operators Namespaces & Assemblies Arrays Preprocessors Delegates and Events Boxing and Unboxing Regular Expression Collections Multithreading Programming Memory Management Exceptions Handling Win Forms Working with database ASP .NET Server Controls and client-side scripts ASP .NET Web Server Controls Validation Controls Principles of database management Need of RDBMS etc Client/Server Computing RDBMS Technologies Codd’s Rules Data Models Normalization Techniques ER Diagrams Data Flow Diagrams Database recovery & backup SQL Android Application 80 Hours Introduction of android Why develop for android Android SDK features Creating android activities Fundamental android UI design Intents, adapters, dialogs Android Technique for saving data Data base in Androids Maps, Geocoding, Location based services Toast, using alarms, Instant messaging Using blue tooth Using Telephony Introducing sensor manager Managing network and wi-fi connection Advanced androids development Linux kernel security Implement AIDL Interface. Project 120 Hours

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  • Big Data – Operational Databases Supporting Big Data – Columnar, Graph and Spatial Database – Day 14 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Key-Value Pair Databases and Document Databases in the Big Data Story. In this article we will understand the role of Columnar, Graph and Spatial Database supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (The day before yesterday’s post) NoSQL Databases (The day before yesterday’s post) Key-Value Pair Databases (Yesterday’s post) Document Databases (Yesterday’s post) Columnar Databases (Tomorrow’s post) Graph Databases (Today’s post) Spatial Databases (Today’s post) Columnar Databases  Relational Database is a row store database or a row oriented database. Columnar databases are column oriented or column store databases. As we discussed earlier in Big Data we have different kinds of data and we need to store different kinds of data in the database. When we have columnar database it is very easy to do so as we can just add a new column to the columnar database. HBase is one of the most popular columnar databases. It uses Hadoop file system and MapReduce for its core data storage. However, remember this is not a good solution for every application. This is particularly good for the database where there is high volume incremental data is gathered and processed. Graph Databases For a highly interconnected data it is suitable to use Graph Database. This database has node relationship structure. Nodes and relationships contain a Key Value Pair where data is stored. The major advantage of this database is that it supports faster navigation among various relationships. For example, Facebook uses a graph database to list and demonstrate various relationships between users. Neo4J is one of the most popular open source graph database. One of the major dis-advantage of the Graph Database is that it is not possible to self-reference (self joins in the RDBMS terms) and there might be real world scenarios where this might be required and graph database does not support it. Spatial Databases  We all use Foursquare, Google+ as well Facebook Check-ins for location aware check-ins. All the location aware applications figure out the position of the phone with the help of Global Positioning System (GPS). Think about it, so many different users at different location in the world and checking-in all together. Additionally, the applications now feature reach and users are demanding more and more information from them, for example like movies, coffee shop or places see. They are all running with the help of Spatial Databases. Spatial data are standardize by the Open Geospatial Consortium known as OGC. Spatial data helps answering many interesting questions like “Distance between two locations, area of interesting places etc.” When we think of it, it is very clear that handing spatial data and returning meaningful result is one big task when there are millions of users moving dynamically from one place to another place & requesting various spatial information. PostGIS/OpenGIS suite is very popular spatial database. It runs as a layer implementation on the RDBMS PostgreSQL. This makes it totally unique as it offers best from both the worlds. Courtesy: mushroom network Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Hive. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Simple MVVM Walkthrough – Refactored

    - by Sean Feldman
    JR has put together a good introduction post into MVVM pattern. I love kick start examples that serve the purpose well. And even more than that I love examples that also can pass the real world projects check. So I took the sample code and refactored it slightly for a few aspects that a lot of developers might raise a brow. Michael has mentioned model (entity) visibility from view. I agree on that. A few other items that don’t settle are using property names as string (magical strings) and Saver class internal casting of a parameter (custom code for each Saver command). Fixing a property names usage is a straight forward exercise – leverage expressions. Something simple like this would do the initial job: class PropertyOf<T> { public static string Resolve(Expression<Func<T, object>> expression) { var member = expression.Body as MemberExpression; return member.Member.Name; } } With this, refactoring of properties names becomes an easy task, with confidence that an old property name string will not get left behind. An updated Invoice would look like this: public class Invoice : INotifyPropertyChanged { private int id; private string receiver; public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } public int Id { get { return id; } set { if (id != value) { id = value; OnPropertyChanged(PropertyOf<Invoice>.Resolve(x => x.Id)); } } } public string Receiver { get { return receiver; } set { receiver = value; OnPropertyChanged(PropertyOf<Invoice>.Resolve(x => x.Receiver)); } } } For the saver, I decided to change it a little so now it becomes a “view-model agnostic” command, one that can be used for multiple commands/view-models. Updated Saver code now accepts an action at construction time and executes that action. No more black magic internal class Command : ICommand { private readonly Action executeAction; public Command(Action executeAction) { this.executeAction = executeAction; } public bool CanExecute(object parameter) { return true; } public event EventHandler CanExecuteChanged; public void Execute(object parameter) { // no more black magic executeAction(); } } Change in InvoiceViewModel is instantiation of Saver command and execution action for the specific command. public ICommand SaveCommand { get { if (saveCommand == null) saveCommand = new Command(ExecuteAction); return saveCommand; } set { saveCommand = value; } } private void ExecuteAction() { DisplayMessage = string.Format("Thanks for creating invoice: {0} {1}", Invoice.Id, Invoice.Receiver); } This way internal knowledge of InvoiceViewModel remains in InvoiceViewModel and Command (ex-Saver) is view-model agnostic. Now the sample is not only a good introduction, but also has some practicality in it. My 5 cents on the subject. Sample code MvvmSimple2.zip

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  • Rethinking Oracle Optimizer Statistics for P6 Part 2

    - by Brian Diehl
    In the previous post (Part 1), I tried to draw some key insights about the relationship between P6 and Oracle Optimizer Statistics.  The first is that average cardinality has the greatest impact on query optimization and that the particular queries generated by P6 are more likely to use this average during calculations. The second is that these are statistics that are unlikely to change greatly over the life of the application. Ultimately, our goal is to get the best query optimization possible.  Or is it? Stability No application administrator wants to get the call at 9am that their application users cannot get there work done because everything is running slow. This is a possibility with a regularly scheduled nightly collection of statistics. It may not just be slow performance, but a complete loss of service because one or more queries are optimized poorly. Ideally, this should not be the case. The database optimizer should make better decisions with more up-to-date data. Better statistics may give incremental performance benefit. However, this benefit must be balanced against the potential cost of system down time.  It is stability that we ultimately desire and not absolute optimal performance. We do want the benefit from more accurate statistics and better query plans, but not at the risk of an unusable system. As a result, I've developed the following methodology around managing database statistics for the P6 database.  1. No Automatic Re-Gathering - The daily, weekly, or other interval of statistic gathering is unlikely to be beneficial. Quite the opposite. It is more likely to cause problems. 2. Smart Re-Gathering - The time to collect statistics is when things have changed significantly. For a new installation of P6, this is happening more often because the data is growing from a few rows to thousands and more. But for a mature system, the data is not changing significantly from week-to-week. There are times to collect statistics: New releases of the application Changes in the underlying hardware or software versions (ex. new Oracle RDBMS version) When additional user groups are added. The new groups may use the software in significantly different ways. After significant changes in the data. This may be monthly, quarterly or yearly.  3. Always Test - If you take away one thing from this post, it would be to always have a plan to test after changing statistics. In reality, statistics can be collected as often as you desire provided there are tests in place to verify that performance is the same or better. These might be automated tests or simply a manual script of application functions. 4. Have a Way Out - Never change the statistics without a way to return to the previous set. Think of the statistics as one part of the overall application code that also includes the source code--both application and RDBMS. It would be foolish to change to the new code without a way to get back to the previous version. In the final post, I will talk about the actual script I created for P6 PMDB and possible future direction for managing query performance. 

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  • ??AMDU?????MOUNT?DISKGROUP???????

    - by Liu Maclean(???)
    AMDU?ORACLE??ASM??????????,????ASM Metadata Dump Utility(AMDU) AMDU??????????: 1. ?ASM DISK?????????????????2. ?ASM?????????????OS????,Diskgroup??mount??3. ????????,???C?????16????? ?????????AMDU??ASM DISKGROUP??????; ASM???????????????, ?????????????,?????????ASM????? ??DISKGROUP??MOUNT????????????????????????? AMDU???????, ????????ASM DISKGROUP ??MOUNT???????,???RDBMS?????ASM??????? ?? AMDU???11g??????,?????10g?ASM ???? ???????????, ORACLE DATABASE?SPFILE?CONTROLFILE?DATAFILE????ASM DISKGROUP?,?????ASM ORA-600??????MOUNT?DISKGROUP, ???????AMDU??????ASM DISK?????? ?? 1 ??? ??SPFILE?CONTROLFILE?DATAFILE ????: ???????SPFILE ,????SPFILE??PFILE???,?????????????control_files??? SQL> show parameter control_files NAME TYPE VALUE———————————— ———– ——————————control_files string +DATA/prodb/controlfile/current.260.794687955, +FRA/prodb/controlfile/current.256.794687955 ??control_files ?????ASM???????????,+DATA/prodb/controlfile/current.260.794687955 ?? 260????????+DATA ??DISKGROUP??FILE NUMBER ???????ASM DISK?DISCOVERY PATH??,??????ASM?SPFILE??asm_diskstring ???? [oracle@mlab2 oracle.SupportTools]$ unzip amdu_X86-64.zipArchive: amdu_X86-64.zipinflating: libskgxp11.soinflating: amduinflating: libnnz11.soinflating: libclntsh.so.11.1 [oracle@mlab2 oracle.SupportTools]$ export LD_LIBRARY_PATH=./ [oracle@mlab2 oracle.SupportTools]$ ./amdu -diskstring ‘/dev/asm*’ -extract data.260amdu_2009_10_10_20_19_17/AMDU-00204: Disk N0006 is in currently mounted diskgroup DATAAMDU-00201: Disk N0006: ‘/dev/asm-disk10'AMDU-00204: Disk N0003 is in currently mounted diskgroup DATAAMDU-00201: Disk N0003: ‘/dev/asm-disk5'AMDU-00204: Disk N0002 is in currently mounted diskgroup DATAAMDU-00201: Disk N0002: ‘/dev/asm-disk6' [oracle@mlab2 oracle.SupportTools]$ cd amdu_2009_10_10_20_19_17/[oracle@mlab2 amdu_2009_10_10_20_19_17]$ lsDATA_260.f report.txt[oracle@mlab2 amdu_2009_10_10_20_19_17]$ ls -ltotal 9548-rw-r–r– 1 oracle oinstall 9748480 Oct 10 20:19 DATA_260.f-rw-r–r– 1 oracle oinstall 9441 Oct 10 20:19 report.txt ???????DATA_260.f ??????,?????????startup mount RDBMS??: SQL> alter system set control_files=’/opt/oracle.SupportTools/amdu_2009_10_10_20_19_17/DATA_260.f’ scope=spfile; System altered. SQL> startup force mount;ORACLE instance started. Total System Global Area 1870647296 bytesFixed Size 2229424 bytesVariable Size 452987728 bytesDatabase Buffers 1409286144 bytesRedo Buffers 6144000 bytesDatabase mounted. SQL> select name from v$datafile; NAME——————————————————————————–+DATA/prodb/datafile/system.256.794687873+DATA/prodb/datafile/sysaux.257.794687875+DATA/prodb/datafile/undotbs1.258.794687875+DATA/prodb/datafile/users.259.794687875+DATA/prodb/datafile/example.265.794687995+DATA/prodb/datafile/mactbs.267.794688457 6 rows selected. startup mount???,???v$datafile????????,????????DISKGROUP??FILE NUMBER ???./amdu -diskstring ‘/dev/asm*’ -extract ???? ??????????? [oracle@mlab2 oracle.SupportTools]$ ./amdu -diskstring ‘/dev/asm*’ -extract data.256amdu_2009_10_10_20_22_21/AMDU-00204: Disk N0006 is in currently mounted diskgroup DATAAMDU-00201: Disk N0006: ‘/dev/asm-disk10'AMDU-00204: Disk N0003 is in currently mounted diskgroup DATAAMDU-00201: Disk N0003: ‘/dev/asm-disk5'AMDU-00204: Disk N0002 is in currently mounted diskgroup DATAAMDU-00201: Disk N0002: ‘/dev/asm-disk6' [oracle@mlab2 oracle.SupportTools]$ cd amdu_2009_10_10_20_22_21/[oracle@mlab2 amdu_2009_10_10_20_22_21]$ lsDATA_256.f report.txt[oracle@mlab2 amdu_2009_10_10_20_22_21]$ dbv file=DATA_256.f DBVERIFY: Release 11.2.0.3.0 – Production on Sat Oct 10 20:23:12 2009 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. DBVERIFY – Verification starting : FILE = /opt/oracle.SupportTools/amdu_2009_10_10_20_22_21/DATA_256.f DBVERIFY – Verification complete Total Pages Examined : 90880Total Pages Processed (Data) : 59817Total Pages Failing (Data) : 0Total Pages Processed (Index): 12609Total Pages Failing (Index): 0Total Pages Processed (Other): 3637Total Pages Processed (Seg) : 1Total Pages Failing (Seg) : 0Total Pages Empty : 14817Total Pages Marked Corrupt : 0Total Pages Influx : 0Total Pages Encrypted : 0Highest block SCN : 1125305 (0.1125305)

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  • Wrapping my head around MongoDB, mongomapper and joins...

    - by cbmeeks
    I'm new to MongoDB and I've used RDBMS for years. Anyway, let's say I have the following collections: Realtors many :bookmarks key :name Houses key :address, String key :bathrooms, Integer Properties key :address, String key :landtype, String Bookmark key :notes I want a Realtor to be able to bookmark a House and/or a Property. Notice that Houses and Properties are stand-alone and have no idea about Realtors or Bookmarks. I want the Bookmark to be sort of like a "join table" in MySQL. The Houses/Properties come from a different source so they can't be modified. I would like to be able to do this in Rails: r = Realtor.first r.bookmarks would give me: House1 House2 PropertyABC PropertyOO1 etc... There will be thousands of Houses and Properties. I realize that this is what RDBMS were made for. But there are several reasons why I am using MongoDB so I would like to make this work. Any suggestions on how to do something like this would be appreciated. Thanks!

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  • Are there any NOSQL-compatible CMS projects?

    - by Michael
    This question is partially related to an older question (Any CMS is Google App Engine compatible?) , but is slightly more general. It seems that in most CMS systems, the most fragile failure point is the database. Traditional database implementations scale poorly and will never be able to handle unforeseen spikes of traffic. Since Google App Engine was designed to help even small businesses overcome that problem, I had the same question that was asked earlier this year with less than satisfactory answers. But more generally, where are the CMS projects that support NOSQL databases? Looking over Wikipedia's list of CMS platforms, I see without much effort that only traditional RDBMS are supported by every single vendor on the list. I would have expected to see at least one or two projects handling CouchDB or similar engines. I understand the complexities of implementing a NOSQL solution to a problem that is typically solved using the relations cleanly expressed in any RDBMS, but there seems to be a rather wide market gap. Since databases are, today, easily outsourced to Google, Amazon, and others which use NOSQL models, I am amazed that there are not more projects actively pursuing this path. Am I simply not aware? Can someone please point me to projects that have real momentum that are developing on this path? I'm looking for two things: a CMS that has as its backbone a NOSQL database enabling easy database outsourcing (hosted MySQL clusters and similar solutions are not what I'm looking for) a project that is built to run on either a PaaS architecture like Google App Engine or an IaaS architecture like Amazon EC2 Any pointers in that direction would be most welcome.

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  • SQL - table alias scope.

    - by Support - multilanguage SO
    I've just learned ( yesterday ) to use "exists" instead of "in". BAD select * from table where nameid in ( select nameid from othertable where otherdesc = 'SomeDesc' ) GOOD select * from table t where exists ( select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeDesc' ) And I have some questions about this: 1) The explanation as I understood was: "The reason why this is better is because only the matching values will be returned instead of building a massive list of possible results". Does that mean that while the first subquery might return 900 results the second will return only 1 ( yes or no )? 2) In the past I have had the RDBMS complainin: "only the first 1000 rows might be retrieved", this second approach would solve that problem? 3) What is the scope of the alias in the second subquery?... does the alias only lives in the parenthesis? for example select * from table t where exists ( select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeDesc' ) AND select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeOtherDesc' ) That is, if I use the same alias ( o for table othertable ) In the second "exist" will it present any problem with the first exists? or are they totally independent? Is this something Oracle only related or it is valid for most RDBMS? Thanks a lot

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  • Best practices to deal with "slightly different" branches of source code

    - by jedi_coder
    This question is rather agnostic than related to a certain version control program. Assume there is a source code tree under certain distributed version control. Let's call it A. At some point somebody else clones it and gets its own copy. Let's call it B. I'll call A and B branches, even if some version control tools have different definitions for branches (some might call A and B repositories). Let's assume that branch A is the "main" branch. In the context of distributed version control this only means that branch A is modified much more actively and the owner of branch B periodically syncs (pulls) new updates from branch A. Let's consider that a certain source file in branch B contains a class (again, it's also language agnostic). The owner of branch B considers that some class methods are more appropriate and groups them together by moving them inside the class body. Functionally nothing has changed - this is a very trivial refactoring of the code. But the change gets reflected in diffs. Now, assuming that this change from branch B will never get merged into branch A, the owner of branch B will always get this difference when pulling from branch A and merging into his own workspace. Even if there's only one such trivial change, the owner of branch B needs to resolve conflicts every time when pulling from branch A. As long as branches A and B are modified independently, more and more conflicts like this appear. What is the workaround for this situation? Which workflow should the owner of branch B follow to minimize the effort for periodically syncing with branch A?

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  • What are the best browser based administration tools for Linux?

    - by Kevin Kuphal
    Looking for recommendations the best comprehensive browser based administration tool for administering a Linux machine. Ideally this would be distribution agnostic. This could also be an "appliance" type product that would administer multiple machines on network. This is marked community wiki. Give your answer preferably one product per answer and vote up packages that you recommend also.

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  • Placement of command line options in bash

    - by Nathan Rambeck
    I just starting using a Mac and have been frustrated that command line options are required immediately following the command so that this works: ls -la /usr but this doesn't: ls /usr -la ls: -la: No such file or directory Is there any way to change this? Or can someone tell me why the placement of options is agnostic on most Linux platforms, but not on Mac?

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  • Is it possible to install custom software on Amazon EC2

    - by quickquestioner
    I'm trudging through the Amazon docs for a quick answer, but while I'm looking I thought it wouldn't hurt to ask here. My client uses custom software that uses (wait for it) Microsoft Excel to store data as opposed a RDBMS. Either way, their server is outdated and they are interested in using Amazon's cloud services, but would installing this software be possible, or am I barking up the wrong tree? Links are welcome! Thanks for your help!

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  • Automatically disable devices to save power and mitigate DMA attack in Windows 7

    - by Martheen Cahya Paulo
    Some OEM include energy saving apps that can switch off certain devices such as webcam or optical drive. Is there any brand-agnostic app out there that can do it? If the list of disabled device is customizable, it would be useful too for mitigating DMA attack (disabling Firewire, PCMCIA, SDIO, Thunderbolt, etc). Even better if it can recognize lock/logoff event, to mimic OSX behavior in mitigating the DMA attack.

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  • Big Data – Buzz Words: Importance of Relational Database in Big Data World – Day 9 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is HDFS. In this article we will take a quick look at the importance of the Relational Database in Big Data world. A Big Question? Here are a few questions I often received since the beginning of the Big Data Series - Does the relational database have no space in the story of the Big Data? Does relational database is no longer relevant as Big Data is evolving? Is relational database not capable to handle Big Data? Is it true that one no longer has to learn about relational data if Big Data is the final destination? Well, every single time when I hear that one person wants to learn about Big Data and is no longer interested in learning about relational database, I find it as a bit far stretched. I am not here to give ambiguous answers of It Depends. I am personally very clear that one who is aspiring to become Big Data Scientist or Big Data Expert they should learn about relational database. NoSQL Movement The reason for the NoSQL Movement in recent time was because of the two important advantages of the NoSQL databases. Performance Flexible Schema In personal experience I have found that when I use NoSQL I have found both of the above listed advantages when I use NoSQL database. There are instances when I found relational database too much restrictive when my data is unstructured as well as they have in the datatype which my Relational Database does not support. It is the same case when I have found that NoSQL solution performing much better than relational databases. I must say that I am a big fan of NoSQL solutions in the recent times but I have also seen occasions and situations where relational database is still perfect fit even though the database is growing increasingly as well have all the symptoms of the big data. Situations in Relational Database Outperforms Adhoc reporting is the one of the most common scenarios where NoSQL is does not have optimal solution. For example reporting queries often needs to aggregate based on the columns which are not indexed as well are built while the report is running, in this kind of scenario NoSQL databases (document database stores, distributed key value stores) database often does not perform well. In the case of the ad-hoc reporting I have often found it is much easier to work with relational databases. SQL is the most popular computer language of all the time. I have been using it for almost over 10 years and I feel that I will be using it for a long time in future. There are plenty of the tools, connectors and awareness of the SQL language in the industry. Pretty much every programming language has a written drivers for the SQL language and most of the developers have learned this language during their school/college time. In many cases, writing query based on SQL is much easier than writing queries in NoSQL supported languages. I believe this is the current situation but in the future this situation can reverse when No SQL query languages are equally popular. ACID (Atomicity Consistency Isolation Durability) – Not all the NoSQL solutions offers ACID compliant language. There are always situations (for example banking transactions, eCommerce shopping carts etc.) where if there is no ACID the operations can be invalid as well database integrity can be at risk. Even though the data volume indeed qualify as a Big Data there are always operations in the application which absolutely needs ACID compliance matured language. The Mixed Bag I have often heard argument that all the big social media sites now a days have moved away from Relational Database. Actually this is not entirely true. While researching about Big Data and Relational Database, I have found that many of the popular social media sites uses Big Data solutions along with Relational Database. Many are using relational databases to deliver the results to end user on the run time and many still uses a relational database as their major backbone. Here are a few examples: Facebook uses MySQL to display the timeline. (Reference Link) Twitter uses MySQL. (Reference Link) Tumblr uses Sharded MySQL (Reference Link) Wikipedia uses MySQL for data storage. (Reference Link) There are many for prominent organizations which are running large scale applications uses relational database along with various Big Data frameworks to satisfy their various business needs. Summary I believe that RDBMS is like a vanilla ice cream. Everybody loves it and everybody has it. NoSQL and other solutions are like chocolate ice cream or custom ice cream – there is a huge base which loves them and wants them but not every ice cream maker can make it just right  for everyone’s taste. No matter how fancy an ice cream store is there is always plain vanilla ice cream available there. Just like the same, there are always cases and situations in the Big Data’s story where traditional relational database is the part of the whole story. In the real world scenarios there will be always the case when there will be need of the relational database concepts and its ideology. It is extremely important to accept relational database as one of the key components of the Big Data instead of treating it as a substandard technology. Ray of Hope – NewSQL In this module we discussed that there are places where we need ACID compliance from our Big Data application and NoSQL will not support that out of box. There is a new termed coined for the application/tool which supports most of the properties of the traditional RDBMS and supports Big Data infrastructure – NewSQL. Tomorrow In tomorrow’s blog post we will discuss about NewSQL. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • On oracle-validated RMP ... do it faster!

    - by [email protected]
    We all know that setting up a Linux host for installing RDBMS can be a really tedious task.Well I wasn't aware that there exists a pre-cooked RPM that installs all the required packages for a fresh install.Ill try to test it soon, in the meantime here you have for downloading it: ( OEL4 and OEL5)http://oss.oracle.com/el5/oracle-validated/http://oss.oracle.com/el4/oracle-validated/More information can be found at the My Oracle Support Note "Linux OS Installation with Reduced Set of Packages for Running Oracle Database Server (Doc ID 728346.1)"Also, check this website http://linux.oracle.com/pls/apex/f?p=102:1:2252801871920376 with a list of Oracle Linux Validated Configurations including software, hardware, storage, and network components along with documented best practicesHope it helps!--L

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  • Global Cache CR Requested But Current Block Received

    - by Liu Maclean(???)
    ????????«MINSCN?Cache Fusion Read Consistent» ????,???????????? ??????????????????: SQL> select * from V$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production PL/SQL Release 11.2.0.3.0 - Production CORE 11.2.0.3.0 Production TNS for Linux: Version 11.2.0.3.0 - Production NLSRTL Version 11.2.0.3.0 - Production SQL> select count(*) from gv$instance; COUNT(*) ---------- 2 SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com ?11gR2 2??RAC??????????status???XG,????Xcurrent block???INSTANCE 2?hold?,?????INSTANCE 1?????????,?????: SQL> select * from test; ID ---------- 1 2 SQL> select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from test; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------ 89233 1 89233 1 SQL> alter system flush buffer_cache; System altered. INSTANCE 1 Session A: SQL> update test set id=id+1 where id=1; 1 row updated. INSTANCE 1 Session B: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1755287 SQL> oradebug setmypid; Statement processed. SQL> oradebug dump gc_elements 255; Statement processed. SQL> oradebug tracefile_name; /s01/orabase/diag/rdbms/vprod/VPROD1/trace/VPROD1_ora_19111.trc GLOBAL CACHE ELEMENT DUMP (address: 0xa4ff3080): id1: 0x15c91 id2: 0x1 pkey: OBJ#76896 block: (1/89233) lock: X rls: 0x0 acq: 0x0 latch: 3 flags: 0x20 fair: 0 recovery: 0 fpin: 'kdswh11: kdst_fetch' bscn: 0x0.146e20 bctx: (nil) write: 0 scan: 0x0 lcp: (nil) lnk: [NULL] lch: [0xa9f6a6f8,0xa9f6a6f8] seq: 32 hist: 58 145:0 118 66 144:0 192 352 197 48 121 113 424 180 58 LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT: flg: 0x02000001 lflg: 0x1 state: XCURRENT tsn: 0 tsh: 2 addr: 0xa9f6a5c8 obj: 76896 cls: DATA bscn: 0x0.1ac898 BH (0xa9f6a5c8) file#: 1 rdba: 0x00415c91 (1/89233) class: 1 ba: 0xa9e56000 set: 5 pool: 3 bsz: 8192 bsi: 0 sflg: 3 pwc: 0,15 dbwrid: 0 obj: 76896 objn: 76896 tsn: 0 afn: 1 hint: f hash: [0x91f4e970,0xbae9d5b8] lru: [0x91f58848,0xa9f6a828] lru-flags: debug_dump obj-flags: object_ckpt_list ckptq: [0x9df6d1d8,0xa9f6a740] fileq: [0xa2ece670,0xbdf4ed68] objq: [0xb4964e00,0xb4964e00] objaq: [0xb4964de0,0xb4964de0] st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 2 le: 0xa4ff3080 flags: buffer_dirty redo_since_read LRBA: [0x19.5671.0] LSCN: [0x0.1ac898] HSCN: [0x0.1ac898] HSUB: [1] buffer tsn: 0 rdba: 0x00415c91 (1/89233) scn: 0x0000.001ac898 seq: 0x01 flg: 0x00 tail: 0xc8980601 frmt: 0x02 chkval: 0x0000 type: 0x06=trans data ??????block: (1/89233)?GLOBAL CACHE ELEMENT DUMP?LOCK????X ??XG , ??????Current Block????Instance??modify???,????????????? ????Instance 2 ????: Instance 2 Session C: SQL> update test set id=id+1 where id=2; 1 row updated. Instance 2 Session D: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1756658 SQL> oradebug setmypid; Statement processed. SQL> oradebug dump gc_elements 255; Statement processed. SQL> oradebug tracefile_name; /s01/orabase/diag/rdbms/vprod/VPROD2/trace/VPROD2_ora_13038.trc GLOBAL CACHE ELEMENT DUMP (address: 0x89fb25a0): id1: 0x15c91 id2: 0x1 pkey: OBJ#76896 block: (1/89233) lock: XG rls: 0x0 acq: 0x0 latch: 3 flags: 0x20 fair: 0 recovery: 0 fpin: 'kduwh01: kdusru' bscn: 0x0.1acdf3 bctx: (nil) write: 0 scan: 0x0 lcp: (nil) lnk: [NULL] lch: [0x96f4cf80,0x96f4cf80] seq: 61 hist: 324 21 143:0 19 16 352 329 144:6 14 7 352 197 LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT: flg: 0x0a000001 state: XCURRENT tsn: 0 tsh: 1 addr: 0x96f4ce50 obj: 76896 cls: DATA bscn: 0x0.1acdf6 BH (0x96f4ce50) file#: 1 rdba: 0x00415c91 (1/89233) class: 1 ba: 0x96bd4000 set: 5 pool: 3 bsz: 8192 bsi: 0 sflg: 2 pwc: 0,15 dbwrid: 0 obj: 76896 objn: 76896 tsn: 0 afn: 1 hint: f hash: [0x96ee1fe8,0xbae9d5b8] lru: [0x96f4d0b0,0x96f4cdc0] obj-flags: object_ckpt_list ckptq: [0xbdf519b8,0x96f4d5a8] fileq: [0xbdf519d8,0xbdf519d8] objq: [0xb4a47b90,0xb4a47b90] objaq: [0x96f4d0e8,0xb4a47b70] st: XCURRENT md: NULL fpin: 'kduwh01: kdusru' tch: 1 le: 0x89fb25a0 flags: buffer_dirty redo_since_read remote_transfered LRBA: [0x11.9e18.0] LSCN: [0x0.1acdf6] HSCN: [0x0.1acdf6] HSUB: [1] buffer tsn: 0 rdba: 0x00415c91 (1/89233) scn: 0x0000.001acdf6 seq: 0x01 flg: 0x00 tail: 0xcdf60601 frmt: 0x02 chkval: 0x0000 type: 0x06=trans data GCS CLIENT 0x89fb2618,6 resp[(nil),0x15c91.1] pkey 76896.0 grant 2 cvt 0 mdrole 0x42 st 0x100 lst 0x20 GRANTQ rl G0 master 1 owner 2 sid 0 remote[(nil),0] hist 0x94121c601163423c history 0x3c.0x4.0xd.0xb.0x1.0xc.0x7.0x9.0x14.0x1. cflag 0x0 sender 1 flags 0x0 replay# 0 abast (nil).x0.1 dbmap (nil) disk: 0x0000.00000000 write request: 0x0000.00000000 pi scn: 0x0000.00000000 sq[(nil),(nil)] msgseq 0x1 updseq 0x0 reqids[6,0,0] infop (nil) lockseq x2b8 pkey 76896.0 hv 93 [stat 0x0, 1->1, wm 32768, RMno 0, reminc 18, dom 0] kjga st 0x4, step 0.0.0, cinc 20, rmno 6, flags 0x0 lb 0, hb 0, myb 15250, drmb 15250, apifrz 0 ?Instance 2??????block: (1/89233)? GLOBAL CACHE ELEMENT Lock Convert?lock: XG ????GC_ELEMENTS DUMP???XCUR Cache Fusion?,???????X$ VIEW,??? X$LE X$KJBR X$KJBL, ???X$ VIEW???????????????????: INSTANCE 2 Session D: SELECT * FROM x$le WHERE le_addr IN (SELECT le_addr FROM x$bh WHERE obj IN (SELECT data_object_id FROM dba_objects WHERE owner = 'SYS' AND object_name = 'TEST') AND class = 1 AND state != 3); ADDR INDX INST_ID LE_ADDR LE_ID1 LE_ID2 ---------------- ---------- ---------- ---------------- ---------- ---------- LE_RLS LE_ACQ LE_FLAGS LE_MODE LE_WRITE LE_LOCAL LE_RECOVERY ---------- ---------- ---------- ---------- ---------- ---------- ----------- LE_BLKS LE_TIME LE_KJBL ---------- ---------- ---------------- 00007F94CA14CF60 7003 2 0000000089FB25A0 89233 1 0 0 32 2 0 1 0 1 0 0000000089FB2618 PCM Resource NAME?[ID1][ID2],[BL]???, ID1?ID2 ??blockno? fileno????, ??????????GC_elements dump?? id1: 0x15c91 id2: 0×1 pkey: OBJ#76896 block: (1/89233)?? ,?  kjblname ? kjbrname ??”[0x15c91][0x1],[BL]” ??: INSTANCE 2 Session D: SQL> set linesize 80 pagesize 1400 SQL> SELECT * 2 FROM x$kjbl l 3 WHERE l.kjblname LIKE '%[0x15c91][0x1],[BL]%'; ADDR INDX INST_ID KJBLLOCKP KJBLGRANT KJBLREQUE ---------------- ---------- ---------- ---------------- --------- --------- KJBLROLE KJBLRESP KJBLNAME ---------- ---------------- ------------------------------ KJBLNAME2 KJBLQUEUE ------------------------------ ---------- KJBLLOCKST KJBLWRITING ---------------------------------------------------------------- ----------- KJBLREQWRITE KJBLOWNER KJBLMASTER KJBLBLOCKED KJBLBLOCKER KJBLSID KJBLRDOMID ------------ ---------- ---------- ----------- ----------- ---------- ---------- KJBLPKEY ---------- 00007F94CA22A288 451 2 0000000089FB2618 KJUSEREX KJUSERNL 0 00 [0x15c91][0x1],[BL][ext 0x0,0x 89233,1,BL 0 GRANTED 0 0 1 0 0 0 0 0 76896 SQL> SELECT r.* FROM x$kjbr r WHERE r.kjbrname LIKE '%[0x15c91][0x1],[BL]%'; no rows selected Instance 1 session B: SQL> SELECT r.* FROM x$kjbr r WHERE r.kjbrname LIKE '%[0x15c91][0x1],[BL]%'; ADDR INDX INST_ID KJBRRESP KJBRGRANT KJBRNCVL ---------------- ---------- ---------- ---------------- --------- --------- KJBRROLE KJBRNAME KJBRMASTER KJBRGRANTQ ---------- ------------------------------ ---------- ---------------- KJBRCVTQ KJBRWRITER KJBRSID KJBRRDOMID KJBRPKEY ---------------- ---------------- ---------- ---------- ---------- 00007F801ACA68F8 1355 1 00000000B5A62AE0 KJUSEREX KJUSERNL 0 [0x15c91][0x1],[BL][ext 0x0,0x 0 00000000B48BB330 00 00 0 0 76896 ??????Instance 1???block: (1/89233),??????Instance 2 build cr block ????Instance 1, ?????????? ????? Instance 1? Foreground Process ? Instance 2?LMS??????RAC  TRACE: Instance 2: [oracle@vrh2 ~]$ ps -ef|grep ora_lms|grep -v grep oracle 23364 1 0 Apr29 ? 00:33:15 ora_lms0_VPROD2 SQL> oradebug setospid 23364 Oracle pid: 13, Unix process pid: 23364, image: [email protected] (LMS0) SQL> oradebug event 10046 trace name context forever,level 8:10708 trace name context forever,level 103: trace[rac.*] disk high; Statement processed. SQL> oradebug tracefile_name /s01/orabase/diag/rdbms/vprod/VPROD2/trace/VPROD2_lms0_23364.trc Instance 1 session B : SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1756658 3 1756661 3 1755287 Instance 1 session A : SQL> alter session set events '10046 trace name context forever,level 8:10708 trace name context forever,level 103: trace[rac.*] disk high'; Session altered. SQL> select * from test; ID ---------- 2 2 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1761520 ?x$BH?????,???????Instance 1???build??CR block,????? TRACE ??: Instance 1 foreground Process: PARSING IN CURSOR #140336527348792 len=18 dep=0 uid=0 oct=3 lid=0 tim=1335939136125254 hv=1689401402 ad='b1a4c828' sqlid='c99yw1xkb4f1u' select * from test END OF STMT PARSE #140336527348792:c=2999,e=2860,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=1357081020,tim=1335939136125253 EXEC #140336527348792:c=0,e=40,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939136125373 WAIT #140336527348792: nam='SQL*Net message to client' ela= 6 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1335939136125420 *** 2012-05-02 02:12:16.125 kclscrs: req=0 block=1/89233 2012-05-02 02:12:16.125574 : kjbcro[0x15c91.1 76896.0][4] *** 2012-05-02 02:12:16.125 kclscrs: req=0 typ=nowait-abort *** 2012-05-02 02:12:16.125 kclscrs: bid=1:3:1:0:f:1e:0:0:10:0:0:0:1:2:4:1:20:0:0:0:c3:49:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:1c:0:4d:26:a3:52:0:0:0:0:c7:c:ca:62:c3:49:0:0:0:0:1:0:14:8e:47:76:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:99:ed:0:0:0:0:0:0:10:0:0:0 2012-05-02 02:12:16.125718 : kjbcro[0x15c91.1 76896.0][4] 2012-05-02 02:12:16.125751 : GSIPC:GMBQ: buff 0xba0ee018, queue 0xbb79a7b8, pool 0x60013fa0, freeq 0, nxt 0xbb79a7b8, prv 0xbb79a7b8 2012-05-02 02:12:16.125780 : kjbsentscn[0x0.1ae0f0][to 2] 2012-05-02 02:12:16.125806 : GSIPC:SENDM: send msg 0xba0ee088 dest x20001 seq 177740 type 36 tkts xff0000 mlen x1680198 2012-05-02 02:12:16.125918 : kjbmscr(0x15c91.1)reqid=0x8(req 0xa4ff30f8)(rinst 1)hldr 2(infosz 200)(lseq x2b8) 2012-05-02 02:12:16.126959 : GSIPC:KSXPCB: msg 0xba0ee088 status 30, type 36, dest 2, rcvr 1 *** 2012-05-02 02:12:16.127 kclwcrs: wait=0 tm=1233 *** 2012-05-02 02:12:16.127 kclwcrs: got 1 blocks from ksxprcv WAIT #140336527348792: nam='gc cr block 2-way' ela= 1233 p1=1 p2=89233 p3=1 obj#=76896 tim=1335939136127199 2012-05-02 02:12:16.127272 : kjbcrcomplete[0x15c91.1 76896.0][0] 2012-05-02 02:12:16.127309 : kjbrcvdscn[0x0.1ae0f0][from 2][idx 2012-05-02 02:12:16.127329 : kjbrcvdscn[no bscn <= rscn 0x0.1ae0f0][from 2] ???? kjbcro[0x15c91.1 76896.0][4] kjbsentscn[0x0.1ae0f0][to 2] ?Instance 2??SCN=1ae0f0=1761520? block: (1/89233),???’gc cr block 2-way’ ??,?????????CR block? Instance 2 LMS TRACE 2012-05-02 02:12:15.634057 : GSIPC:RCVD: ksxp msg 0x7f16e1598588 sndr 1 seq 0.177740 type 36 tkts 0 2012-05-02 02:12:15.634094 : GSIPC:RCVD: watq msg 0x7f16e1598588 sndr 1, seq 177740, type 36, tkts 0 2012-05-02 02:12:15.634108 : GSIPC:TKT: collect msg 0x7f16e1598588 from 1 for rcvr -1, tickets 0 2012-05-02 02:12:15.634162 : kjbrcvdscn[0x0.1ae0f0][from 1][idx 2012-05-02 02:12:15.634186 : kjbrcvdscn[no bscn1, wm 32768, RMno 0, reminc 18, dom 0] kjga st 0x4, step 0.0.0, cinc 20, rmno 6, flags 0x0 lb 0, hb 0, myb 15250, drmb 15250, apifrz 0 GCS CLIENT END 2012-05-02 02:12:15.635211 : kjbdowncvt[0x15c91.1 76896.0][1][options x0] 2012-05-02 02:12:15.635230 : GSIPC:AMBUF: rcv buff 0x7f16e1c56420, pool rcvbuf, rqlen 1103 2012-05-02 02:12:15.635308 : GSIPC:GPBMSG: new bmsg 0x7f16e1c56490 mb 0x7f16e1c56420 msg 0x7f16e1c564b0 mlen 152 dest x101 flushsz -1 2012-05-02 02:12:15.635334 : kjbmslset(0x15c91.1)) seq 0x4 reqid=0x6 (shadow 0xb48bb330.xb)(rsn 2)(mas@1) 2012-05-02 02:12:15.635355 : GSIPC:SPBMSG: send bmsg 0x7f16e1c56490 blen 184 msg 0x7f16e1c564b0 mtype 33 attr|dest x30101 bsz|fsz x1ffff 2012-05-02 02:12:15.635377 : GSIPC:SNDQ: enq msg 0x7f16e1c56490, type 65521 seq 118669, inst 1, receiver 1, queued 1 *** 2012-05-02 02:12:15.635 kclccctx: cleanup copy 0x7f16e1d94798 2012-05-02 02:12:15.635479 : [kjmpmsgi:compl][type 36][msg 0x7f16e1598588][seq 177740.0][qtime 0][ptime 1257] 2012-05-02 02:12:15.635511 : GSIPC:BSEND: flushing sndq 0xb491dd28, id 1, dcx 0xbc516778, inst 1, rcvr 1 qlen 0 1 2012-05-02 02:12:15.635536 : GSIPC:BSEND: no batch1 msg 0x7f16e1c56490 type 65521 len 184 dest (1:1) 2012-05-02 02:12:15.635557 : kjbsentscn[0x0.1ae0f1][to 1] 2012-05-02 02:12:15.635578 : GSIPC:SENDM: send msg 0x7f16e1c56490 dest x10001 seq 118669 type 65521 tkts x10002 mlen xb800e8 WAIT #0: nam='gcs remote message' ela= 180 waittime=1 poll=0 event=0 obj#=0 tim=1335939135635819 2012-05-02 02:12:15.635853 : GSIPC:RCVD: ksxp msg 0x7f16e167e0b0 sndr 1 seq 0.177741 type 32 tkts 0 2012-05-02 02:12:15.635875 : GSIPC:RCVD: watq msg 0x7f16e167e0b0 sndr 1, seq 177741, type 32, tkts 0 2012-05-02 02:12:15.636012 : GSIPC:TKT: collect msg 0x7f16e167e0b0 from 1 for rcvr -1, tickets 0 2012-05-02 02:12:15.636040 : kjbrcvdscn[0x0.1ae0f1][from 1][idx 2012-05-02 02:12:15.636060 : kjbrcvdscn[no bscn <= rscn 0x0.1ae0f1][from 1] 2012-05-02 02:12:15.636082 : GSIPC:TKT: dest (1:1) rtkt not acked 1  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:12:15.636102 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:12:15.636125 : [kjmxmpm][type 32][seq 0.177741][msg 0x7f16e167e0b0][from 1] 2012-05-02 02:12:15.636146 : kjbmpocr(0xb0.6)seq 0x1,reqid=0x23a,(client 0x9fff7b58,0x1)(from 1)(lseq xdf0) 2????LMS????????? ??gcs remote message GSIPC ????SCN=[0x0.1ae0f0] block=1/89233???,??BAST kjbmpbast(0x15c91.1),?? block=1/89233??????? ??fairness??(?11.2.0.3???_fairness_threshold=2),?current block?KCL: F156: fairness downconvert,?Xcurrent DownConvert? Scurrent: Instance 2: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 2 0 3 1756658 ??Instance 2 LMS ?cr block??? kjbmslset(0x15c91.1)) ????SEND QUEUE GSIPC:SNDQ: enq msg 0x7f16e1c56490? ???????Instance 1???? block: (1/89233)??? ??????: Instance 2: SQL> select CURRENT_RESULTS,LIGHT_WORKS from v$cr_block_server; CURRENT_RESULTS LIGHT_WORKS --------------- ----------- 29273 437 Instance 1 session A: SQL> SQL> select * from test; ID ---------- 2 2 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1761942 3 1761932 1 0 3 1761520 Instance 2: SQL> select CURRENT_RESULTS,LIGHT_WORKS from v$cr_block_server; CURRENT_RESULTS LIGHT_WORKS --------------- ----------- 29274 437 select * from test END OF STMT PARSE #140336529675592:c=0,e=337,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939668940051 EXEC #140336529675592:c=0,e=96,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939668940204 WAIT #140336529675592: nam='SQL*Net message to client' ela= 5 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1335939668940348 *** 2012-05-02 02:21:08.940 kclscrs: req=0 block=1/89233 2012-05-02 02:21:08.940676 : kjbcro[0x15c91.1 76896.0][5] *** 2012-05-02 02:21:08.940 kclscrs: req=0 typ=nowait-abort *** 2012-05-02 02:21:08.940 kclscrs: bid=1:3:1:0:f:21:0:0:10:0:0:0:1:2:4:1:20:0:0:0:c3:49:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:1f:0:4d:26:a3:52:0:0:0:0:c7:c:ca:62:c3:49:0:0:0:0:1:0:17:8e:47:76:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:99:ed:0:0:0:0:0:0:10:0:0:0 2012-05-02 02:21:08.940799 : kjbcro[0x15c91.1 76896.0][5] 2012-05-02 02:21:08.940833 : GSIPC:GMBQ: buff 0xba0ee018, queue 0xbb79a7b8, pool 0x60013fa0, freeq 0, nxt 0xbb79a7b8, prv 0xbb79a7b8 2012-05-02 02:21:08.940859 : kjbsentscn[0x0.1ae28c][to 2] 2012-05-02 02:21:08.940870 : GSIPC:SENDM: send msg 0xba0ee088 dest x20001 seq 177810 type 36 tkts xff0000 mlen x1680198 2012-05-02 02:21:08.940976 : kjbmscr(0x15c91.1)reqid=0xa(req 0xa4ff30f8)(rinst 1)hldr 2(infosz 200)(lseq x2b8) 2012-05-02 02:21:08.941314 : GSIPC:KSXPCB: msg 0xba0ee088 status 30, type 36, dest 2, rcvr 1 *** 2012-05-02 02:21:08.941 kclwcrs: wait=0 tm=707 *** 2012-05-02 02:21:08.941 kclwcrs: got 1 blocks from ksxprcv 2012-05-02 02:21:08.941818 : kjbassume[0x15c91.1][sender 2][mymode x1][myrole x0][srole x0][flgs x0][spiscn 0x0.0][swscn 0x0.0] 2012-05-02 02:21:08.941852 : kjbrcvdscn[0x0.1ae28d][from 2][idx 2012-05-02 02:21:08.941871 : kjbrcvdscn[no bscn ??????????????SCN=[0x0.1ae28c]=1761932 Version?CR block, ????receive????Xcurrent Block??SCN=1ae28d=1761933,Instance 1???Xcurrent Block???build????????SCN=1761932?CR BLOCK, ????????Current block,?????????'gc current block 2-way'? ?????????????request current block,?????kjbcro;?????Instance 2?LMS???????Current Block: Instance 2 LMS trace: 2012-05-02 02:21:08.448743 : GSIPC:RCVD: ksxp msg 0x7f16e14a4398 sndr 1 seq 0.177810 type 36 tkts 0 2012-05-02 02:21:08.448778 : GSIPC:RCVD: watq msg 0x7f16e14a4398 sndr 1, seq 177810, type 36, tkts 0 2012-05-02 02:21:08.448798 : GSIPC:TKT: collect msg 0x7f16e14a4398 from 1 for rcvr -1, tickets 0 2012-05-02 02:21:08.448816 : kjbrcvdscn[0x0.1ae28c][from 1][idx 2012-05-02 02:21:08.448834 : kjbrcvdscn[no bscn <= rscn 0x0.1ae28c][from 1] 2012-05-02 02:21:08.448857 : GSIPC:TKT: dest (1:1) rtkt not acked 2  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:21:08.448875 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:21:08.448970 : [kjmxmpm][type 36][seq 0.177810][msg 0x7f16e14a4398][from 1] 2012-05-02 02:21:08.448993 : kjbmpbast(0x15c91.1) reqid=0x6 (req 0xa4ff30f8)(reqinst 1)(reqid 10)(flags x0) *** 2012-05-02 02:21:08.449 kclcrrf: req=48054 block=1/89233 *** 2012-05-02 02:21:08.449 kcl_compress_block: compressed: 6 free space: 7680 2012-05-02 02:21:08.449085 : kjbsentscn[0x0.1ae28d][to 1] 2012-05-02 02:21:08.449142 : kjbdeliver[to 1][0xa4ff30f8][10][current 1] 2012-05-02 02:21:08.449164 : kjbmssch(reqlock 0xa4ff30f8,10)(to 1)(bsz 344) 2012-05-02 02:21:08.449183 : GSIPC:AMBUF: rcv buff 0x7f16e18bcec8, pool rcvbuf, rqlen 1102 *** 2012-05-02 02:21:08.449 kclccctx: cleanup copy 0x7f16e1d94838 *** 2012-05-02 02:21:08.449 kcltouched: touch seconds 3271 *** 2012-05-02 02:21:08.449 kclgrantlk: req=48054 2012-05-02 02:21:08.449347 : [kjmpmsgi:compl][type 36][msg 0x7f16e14a4398][seq 177810.0][qtime 0][ptime 1119] WAIT #0: nam='gcs remote message' ela= 568 waittime=1 poll=0 event=0 obj#=0 tim=1335939668449962 2012-05-02 02:21:08.450001 : GSIPC:RCVD: ksxp msg 0x7f16e1bb22a0 sndr 1 seq 0.177811 type 32 tkts 0 2012-05-02 02:21:08.450024 : GSIPC:RCVD: watq msg 0x7f16e1bb22a0 sndr 1, seq 177811, type 32, tkts 0 2012-05-02 02:21:08.450043 : GSIPC:TKT: collect msg 0x7f16e1bb22a0 from 1 for rcvr -1, tickets 0 2012-05-02 02:21:08.450060 : kjbrcvdscn[0x0.1ae28e][from 1][idx 2012-05-02 02:21:08.450078 : kjbrcvdscn[no bscn <= rscn 0x0.1ae28e][from 1] 2012-05-02 02:21:08.450097 : GSIPC:TKT: dest (1:1) rtkt not acked 3  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:21:08.450116 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:21:08.450136 : [kjmxmpm][type 32][seq 0.177811][msg 0x7f16e1bb22a0][from 1] 2012-05-02 02:21:08.450155 : kjbmpocr(0xb0.6)seq 0x1,reqid=0x23e,(client 0x9fff7b58,0x1)(from 1)(lseq xdf4) ???Instance 2??LMS???,???build cr block,??????Instance 1?????Current Block??????Instance 2??v$cr_block_server??????LIGHT_WORKS?????current block transfer??????,??????? CR server? Light Work Rule(Light Work Rule?8i Cr Server?????????,?Remote LMS?? build CR????????,resource holder?LMS???????block,????CR build If creating the consistent read version block involves too much work (such as reading blocks from disk), then the holder sends the block to the requestor, and the requestor completes the CR fabrication. The holder maintains a fairness counter of CR requests. After the fairness threshold is reached, the holder downgrades it to lock mode.)? ??????? CR Request ????Current Block?? ???:??????class?block,CR server??????? ??undo block?? undo header block?CR quest, LMS????Current Block, ????? ???? ??????? block cleanout? CR  Version??????? ???????? data blocks, ??????? CR quest  & CR received?(???????Light Work Rule,LMS"??"), ??Current Block??DownConvert???S lock,??LMS???????ship??current version?block? ??????? , ?????? ,???????DownConvert?????”_fairness_threshold“???200,????Xcurrent Block?????Scurrent, ????LMS?????Current Version?Data Block: SQL> show parameter fair NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ _fairness_threshold integer 200 Instance 1: SQL> update test set id=id+1 where id=4; 1 row updated. Instance 2: SQL> update test set id=id+1 where id=2; 1 row updated. SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1838166 ?Instance 1? ????,? ??instance 2? v$cr_block_server?? instance 1 SQL> select * from test; ID ---------- 10 3 instance 2: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1883707 8 0 SQL> select * from test; ID ---------- 10 3 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1883707 8 0 ................... SQL> / STATE CR_SCN_BAS ---------- ---------- 2 0 3 1883707 3 1883695 repeat cr request on Instance 1 SQL> / STATE CR_SCN_BAS ---------- ---------- 8 0 3 1883707 3 1883695 ??????_fairness_threshold????????,?????200 ????????CR serve??Downgrade?lock, ????data block? CR Request????Receive? Current Block?

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