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• Need help choosing database server

  - by The Pretender

  Good day everyone. Recently I was given a task to develop an application to automate some aspects of stocks trading. While working on initial architecture, the database dilemma emerged. What I need is a fast database engine which can process huge amounts of data coming in very fast. I'm fairly experienced in general programming, but I never faced a task of developing a high-load database architecture. I developed a simple MSSQL database schema with several many-to-many relationships during one of my projects, but that's it. What I'm looking for is some advice on choosing the most suitable database engine and some pointers to various manuals or books which describe high-load database development. Specifics of the project are as follows: OS: Windows NT family (Server 2008 / 7) Primary platform: .NET with C# Database structure: one table to hold primary items and two or three tables with foreign keys to the first table to hold additional information. Database SELECT requirements: Need super-fast selection by foreign keys and by combination of foreign key and one of the columns (presumably DATETIME) Database INSERT requirements: The faster the better :) If there'll be significant performance gain, some parts can be written in C++ with managed interfaces to the rest of the system. So once again: given all that stuff I just typed, please give me some advice on what the best database for my project is. Links or references to some manuals and books on the subject are also greatly appreciated. EDIT: I'll need to insert 3-5 rows in 2 tables approximately once in 30-50 milliseconds and I'll need to do SELECT with 0-2 WHERE clauses queries with similar rate.

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• SQL SERVER – How to Recover SQL Database Data Deleted by Accident

  - by Pinal Dave

  In Repair a SQL Server database using a transaction log explorer, I showed how to use ApexSQL Log, a SQL Server transaction log viewer, to recover a SQL Server database after a disaster. In this blog, I’ll show you how to use another SQL Server disaster recovery tool from ApexSQL in a situation when data is accidentally deleted. You can download ApexSQL Recover here, install, and play along. With a good SQL Server disaster recovery strategy, data recovery is not a problem. You have a reliable full database backup with valid data, a full database backup and subsequent differential database backups, or a full database backup and a chain of transaction log backups. But not all situations are ideal. Here we’ll address some sub-optimal scenarios, where you can still successfully recover data. If you have only a full database backup This is the least optimal SQL Server disaster recovery strategy, as it doesn’t ensure minimal data loss. For example, data was deleted on Wednesday. Your last full database backup was created on Sunday, three days before the records were deleted. By using the full database backup created on Sunday, you will be able to recover SQL database records that existed in the table on Sunday. If there were any records inserted into the table on Monday or Tuesday, they will be lost forever. The same goes for records modified in this period. This method will not bring back modified records, only the old records that existed on Sunday. If you restore this full database backup, all your changes (intentional and accidental) will be lost and the database will be reverted to the state it had on Sunday. What you have to do is compare the records that were in the table on Sunday to the records on Wednesday, create a synchronization script, and execute it against the Wednesday database. If you have a full database backup followed by differential database backups Let’s say the situation is the same as in the example above, only you create a differential database backup every night. Use the full database backup created on Sunday, and the last differential database backup (created on Tuesday). In this scenario, you will lose only the data inserted and updated after the differential backup created on Tuesday. If you have a full database backup and a chain of transaction log backups This is the SQL Server disaster recovery strategy that provides minimal data loss. With a full chain of transaction logs, you can recover the SQL database to an exact point in time. To provide optimal results, you have to know exactly when the records were deleted, because restoring to a later point will not bring back the records. This method requires restoring the full database backup first. If you have any differential log backup created after the last full database backup, restore the most recent one. Then, restore transaction log backups, one by one, it the order they were created starting with the first created after the restored differential database backup. Now, the table will be in the state before the records were deleted. You have to identify the deleted records, script them and run the script against the original database. Although this method is reliable, it is time-consuming and requires a lot of space on disk. How to easily recover deleted records? The following solution enables you to recover SQL database records even if you have no full or differential database backups and no transaction log backups. To understand how ApexSQL Recover works, I’ll explain what happens when table data is deleted. Table data is stored in data pages. When you delete table records, they are not immediately deleted from the data pages, but marked to be overwritten by new records. Such records are not shown as existing anymore, but ApexSQL Recover can read them and create undo script for them. How long will deleted records stay in the MDF file? It depends on many factors, as time passes it’s less likely that the records will not be overwritten. The more transactions occur after the deletion, the more chances the records will be overwritten and permanently lost. Therefore, it’s recommended to create a copy of the database MDF and LDF files immediately (if you cannot take your database offline until the issue is solved) and run ApexSQL Recover on them. Note that a full database backup will not help here, as the records marked for overwriting are not included in the backup. First, I’ll delete some records from the Person.EmailAddress table in the AdventureWorks database.   I can delete these records in SQL Server Management Studio, or execute a script such as DELETE FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 Then, I’ll start ApexSQL Recover and select From DELETE operation in the Recovery tab.   In the Select the database to recover step, first select the SQL Server instance. If it’s not shown in the drop-down list, click the Server icon right to the Server drop-down list and browse for the SQL Server instance, or type the instance name manually. Specify the authentication type and select the database in the Database drop-down list.   In the next step, you’re prompted to add additional data sources. As this can be a tricky step, especially for new users, ApexSQL Recover offers help via the Help me decide option.   The Help me decide option guides you through a series of questions about the database transaction log and advises what files to add. If you know that you have no transaction log backups or detached transaction logs, or the online transaction log file has been truncated after the data was deleted, select No additional transaction logs are available. If you know that you have transaction log backups that contain the delete transactions you want to recover, click Add transaction logs. The online transaction log is listed and selected automatically.   Click Add if to add transaction log backups. It would be best if you have a full transaction log chain, as explained above. The next step for this option is to specify the time range.   Selecting a small time range for the time of deletion will create the recovery script just for the accidentally deleted records. A wide time range might script the records deleted on purpose, and you don’t want that. If needed, you can check the script generated and manually remove such records. After that, for all data sources options, the next step is to select the tables. Be careful here, if you deleted some data from other tables on purpose, and don’t want to recover them, don’t select all tables, as ApexSQL Recover will create the INSERT script for them too.   The next step offers two options: to create a recovery script that will insert the deleted records back into the Person.EmailAddress table, or to create a new database, create the Person.EmailAddress table in it, and insert the deleted records. I’ll select the first one.   The recovery process is completed and 11 records are found and scripted, as expected.   To see the script, click View script. ApexSQL Recover has its own script editor, where you can review, modify, and execute the recovery script. The insert into statements look like: INSERT INTO Person.EmailAddress( BusinessEntityID, EmailAddressID, EmailAddress, rowguid, ModifiedDate) VALUES( 70, 70, N'[email protected]' COLLATE SQL_Latin1_General_CP1_CI_AS, 'd62c5b4e-c91f-403f-b630-7b7e0fda70ce', '20030109 00:00:00.000' ); To execute the script, click Execute in the menu.   If you want to check whether the records are really back, execute SELECT * FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 As shown, ApexSQL Recover recovers SQL database data after accidental deletes even without the database backup that contains the deleted data and relevant transaction log backups. ApexSQL Recover reads the deleted data from the database data file, so this method can be used even for databases in the Simple recovery model. Besides recovering SQL database records from a DELETE statement, ApexSQL Recover can help when the records are lost due to a DROP TABLE, or TRUNCATE statement, as well as repair a corrupted MDF file that cannot be attached to as SQL Server instance. You can find more information about how to recover SQL database lost data and repair a SQL Server database on ApexSQL Solution center. There are solutions for various situations when data needs to be recovered. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Curing the Database-Application mismatch

  - by Phil Factor

  If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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• Generating EF Code First model classes from an existing database

  - by Jon Galloway

  Entity Framework Code First is a lightweight way to "turn on" data access for a simple CLR class. As the name implies, the intended use is that you're writing the code first and thinking about the database later. However, I really like the Entity Framework Code First works, and I want to use it in existing projects and projects with pre-existing databases. For example, MVC Music Store comes with a SQL Express database that's pre-loaded with a catalog of music (including genres, artists, and songs), and while it may eventually make sense to load that seed data from a different source, for the MVC 3 release we wanted to keep using the existing database. While I'm not getting the full benefit of Code First - writing code which drives the database schema - I can still benefit from the simplicity of the lightweight code approach. Scott Guthrie blogged about how to use entity framework with an existing database, looking at how you can override the Entity Framework Code First conventions so that it can work with a database which was created following other conventions. That gives you the information you need to create the model classes manually. However, it turns out that with Entity Framework 4 CTP 5, there's a way to generate the model classes from the database schema. Once the grunt work is done, of course, you can go in and modify the model classes as you'd like, but you can save the time and frustration of figuring out things like mapping SQL database types to .NET types. Note that this template requires Entity Framework 4 CTP 5 or later. You can install EF 4 CTP 5 here. Step One: Generate an EF Model from your existing database The code generation system in Entity Framework works from a model. You can add a model to your existing project and delete it when you're done, but I think it's simpler to just spin up a separate project to generate the model classes. When you're done, you can delete the project without affecting your application, or you may choose to keep it around in case you have other database schema updates which require model changes. I chose to add the Model classes to the Models folder of a new MVC 3 application. Right-click the folder and select "Add / New Item..."   Next, select ADO.NET Entity Data Model from the Data Templates list, and name it whatever you want (the name is unimportant).   Next, select "Generate from database." This is important - it's what kicks off the next few steps, which read your database's schema.   Now it's time to point the Entity Data Model Wizard at your existing database. I'll assume you know how to find your database - if not, I covered that a bit in the MVC Music Store tutorial section on Models and Data. Select your database, uncheck the "Save entity connection settings in Web.config" (since we won't be using them within the application), and click Next.   Now you can select the database objects you'd like modeled. I just selected all tables and clicked Finish.   And there's your model. If you want, you can make additional changes here before going on to generate the code.   Step Two: Add the DbContext Generator Like most code generation systems in Visual Studio lately, Entity Framework uses T4 templates which allow for some control over how the code is generated. K Scott Allen wrote a detailed article on T4 Templates and the Entity Framework on MSDN recently, if you'd like to know more. Fortunately for us, there's already a template that does just what we need without any customization. Right-click a blank space in the Entity Framework model surface and select "Add Code Generation Item..." Select the Code groupt in the Installed Templates section and pick the ADO.NET DbContext Generator. If you don't see this listed, make sure you've got EF 4 CTP 5 installed and that you're looking at the Code templates group. Note that the DbContext Generator template is similar to the EF POCO template which came out last year, but with "fix up" code (unnecessary in EF Code First) removed.   As soon as you do this, you'll two terrifying Security Warnings - unless you click the "Do not show this message again" checkbox the first time. It will also be displayed (twice) every time you rebuild the project, so I checked the box and no immediate harm befell my computer (fingers crossed!).   Here's the payoff: two templates (filenames ending with .tt) have been added to the project, and they've generated the code I needed.   The "MusicStoreEntities.Context.tt" template built a DbContext class which holds the entity collections, and the "MusicStoreEntities.tt" template build a separate class for each table I selected earlier. We'll customize them in the next step. I recommend copying all the generated .cs files into your application at this point, since accidentally rebuilding the generation project will overwrite your changes if you leave them there. Step Three: Modify and use your POCO entity classes Note: I made a bunch of tweaks to my POCO classes after they were generated. You don't have to do any of this, but I think it's important that you can - they're your classes, and EF Code First respects that. Modify them as you need for your application, or don't. The Context class derives from DbContext, which is what turns on the EF Code First features. It holds a DbSet for each entity. Think of DbSet as a simple List, but with Entity Framework features turned on.   //------------------------------------------------------------------------------ // <auto-generated> // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Data.Entity; public partial class Entities : DbContext { public Entities() : base("name=Entities") { } public DbSet<Album> Albums { get; set; } public DbSet<Artist> Artists { get; set; } public DbSet<Cart> Carts { get; set; } public DbSet<Genre> Genres { get; set; } public DbSet<OrderDetail> OrderDetails { get; set; } public DbSet<Order> Orders { get; set; } } } It's a pretty lightweight class as generated, so I just took out the comments, set the namespace, removed the constructor, and formatted it a bit. Done. If I wanted, though, I could have added or removed DbSets, overridden conventions, etc. using System.Data.Entity; namespace MvcMusicStore.Models { public class MusicStoreEntities : DbContext { public DbSet Albums { get; set; } public DbSet Genres { get; set; } public DbSet Artists { get; set; } public DbSet Carts { get; set; } public DbSet Orders { get; set; } public DbSet OrderDetails { get; set; } } } Next, it's time to look at the individual classes. Some of mine were pretty simple - for the Cart class, I just need to remove the header and clean up the namespace. //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Cart { // Primitive properties public int RecordId { get; set; } public string CartId { get; set; } public int AlbumId { get; set; } public int Count { get; set; } public System.DateTime DateCreated { get; set; } // Navigation properties public virtual Album Album { get; set; } } } I did a bit more customization on the Album class. Here's what was generated: //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Album { public Album() { this.Carts = new HashSet(); this.OrderDetails = new HashSet(); } // Primitive properties public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } // Navigation properties public virtual Artist Artist { get; set; } public virtual Genre Genre { get; set; } public virtual ICollection Carts { get; set; } public virtual ICollection OrderDetails { get; set; } } } I removed the header, changed the namespace, and removed some of the navigation properties. One nice thing about EF Code First is that you don't have to have a property for each database column or foreign key. In the Music Store sample, for instance, we build the app up using code first and start with just a few columns, adding in fields and navigation properties as the application needs them. EF Code First handles the columsn we've told it about and doesn't complain about the others. Here's the basic class: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { public class Album { public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List OrderDetails { get; set; } } } It's my class, not Entity Framework's, so I'm free to do what I want with it. I added a bunch of MVC 3 annotations for scaffolding and validation support, as shown below: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { [Bind(Exclude = "AlbumId")] public class Album { [ScaffoldColumn(false)] public int AlbumId { get; set; } [DisplayName("Genre")] public int GenreId { get; set; } [DisplayName("Artist")] public int ArtistId { get; set; } [Required(ErrorMessage = "An Album Title is required")] [StringLength(160)] public string Title { get; set; } [Required(ErrorMessage = "Price is required")] [Range(0.01, 100.00, ErrorMessage = "Price must be between 0.01 and 100.00")] public decimal Price { get; set; } [DisplayName("Album Art URL")] [StringLength(1024)] public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List<OrderDetail> OrderDetails { get; set; } } } The end result was that I had working EF Code First model code for the finished application. You can follow along through the tutorial to see how I built up to the finished model classes, starting with simple 2-3 property classes and building up to the full working schema. Thanks to Diego Vega (on the Entity Framework team) for pointing me to the DbContext template.

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• EF Code First - Include(x => x.Properties.Entity) a 1 : Many association

  - by VulgarBinary

  Given a EF-Code First CTP5 entity layout like: public class Person { ... } which has a collection of: public class Address { ... } which has a single association of: public class Mailbox { ... } I want to do: PersonQuery.Include(x => x.Addresses).Include("Addresses.Mailbox") WITHOUT using a magic string. I want to do it using a lambda expression. I am aware what I typed above will compile and will bring back all Persons matching the search criteria with their addresses and each addresses' mailbox eager loaded, but it's in a string which irritates me. How do I do it without a string? Thanks Stack!

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• Class-Level Model Validation with EF Code First and ASP.NET MVC 3

  - by ScottGu

  Earlier this week the data team released the CTP5 build of the new Entity Framework Code-First library.  In my blog post a few days ago I talked about a few of the improvements introduced with the new CTP5 build.  Automatic support for enforcing DataAnnotation validation attributes on models was one of the improvements I discussed.  It provides a pretty easy way to enable property-level validation logic within your model layer. You can apply validation attributes like [Required], [Range], and [RegularExpression] – all of which are built-into .NET 4 – to your model classes in order to enforce that the model properties are valid before they are persisted to a database.  You can also create your own custom validation attributes (like this cool [CreditCard] validator) and have them be automatically enforced by EF Code First as well.  This provides a really easy way to validate property values on your models.  I showed some code samples of this in action in my previous post. Class-Level Model Validation using IValidatableObject DataAnnotation attributes provides an easy way to validate individual property values on your model classes.  Several people have asked - “Does EF Code First also support a way to implement class-level validation methods on model objects, for validation rules than need to span multiple property values?”  It does – and one easy way you can enable this is by implementing the IValidatableObject interface on your model classes. IValidatableObject.Validate() Method Below is an example of using the IValidatableObject interface (which is built-into .NET 4 within the System.ComponentModel.DataAnnotations namespace) to implement two custom validation rules on a Product model class.  The two rules ensure that: New units can’t be ordered if the Product is in a discontinued state New units can’t be ordered if there are already more than 100 units in stock We will enforce these business rules by implementing the IValidatableObject interface on our Product class, and by implementing its Validate() method like so: The IValidatableObject.Validate() method can apply validation rules that span across multiple properties, and can yield back multiple validation errors. Each ValidationResult returned can supply both an error message as well as an optional list of property names that caused the violation (which is useful when displaying error messages within UI). Automatic Validation Enforcement EF Code-First (starting with CTP5) now automatically invokes the Validate() method when a model object that implements the IValidatableObject interface is saved.  You do not need to write any code to cause this to happen – this support is now enabled by default. This new support means that the below code – which violates one of our above business rules – will automatically throw an exception (and abort the transaction) when we call the “SaveChanges()” method on our Northwind DbContext: In addition to reactively handling validation exceptions, EF Code First also allows you to proactively check for validation errors.  Starting with CTP5, you can call the “GetValidationErrors()” method on the DbContext base class to retrieve a list of validation errors within the model objects you are working with.  GetValidationErrors() will return a list of all validation errors – regardless of whether they are generated via DataAnnotation attributes or by an IValidatableObject.Validate() implementation.  Below is an example of proactively using the GetValidationErrors() method to check (and handle) errors before trying to call SaveChanges(): ASP.NET MVC 3 and IValidatableObject ASP.NET MVC 2 included support for automatically honoring and enforcing DataAnnotation attributes on model objects that are used with ASP.NET MVC’s model binding infrastructure.  ASP.NET MVC 3 goes further and also honors the IValidatableObject interface.  This combined support for model validation makes it easy to display appropriate error messages within forms when validation errors occur.  To see this in action, let’s consider a simple Create form that allows users to create a new Product: We can implement the above Create functionality using a ProductsController class that has two “Create” action methods like below: The first Create() method implements a version of the /Products/Create URL that handles HTTP-GET requests - and displays the HTML form to fill-out.  The second Create() method implements a version of the /Products/Create URL that handles HTTP-POST requests - and which takes the posted form data, ensures that is is valid, and if it is valid saves it in the database.  If there are validation issues it redisplays the form with the posted values.  The razor view template of our “Create” view (which renders the form) looks like below: One of the nice things about the above Controller + View implementation is that we did not write any validation logic within it.  The validation logic and business rules are instead implemented entirely within our model layer, and the ProductsController simply checks whether it is valid (by calling the ModelState.IsValid helper method) to determine whether to try and save the changes or redisplay the form with errors. The Html.ValidationMessageFor() helper method calls within our view simply display the error messages our Product model’s DataAnnotations and IValidatableObject.Validate() method returned.  We can see the above scenario in action by filling out invalid data within the form and attempting to submit it: Notice above how when we hit the “Create” button we got an error message.  This was because we ticked the “Discontinued” checkbox while also entering a value for the UnitsOnOrder (and so violated one of our business rules).  You might ask – how did ASP.NET MVC know to highlight and display the error message next to the UnitsOnOrder textbox?  It did this because ASP.NET MVC 3 now honors the IValidatableObject interface when performing model binding, and will retrieve the error messages from validation failures with it. The business rule within our Product model class indicated that the “UnitsOnOrder” property should be highlighted when the business rule we hit was violated: Our Html.ValidationMessageFor() helper method knew to display the business rule error message (next to the UnitsOnOrder edit box) because of the above property name hint we supplied: Keeping things DRY ASP.NET MVC and EF Code First enables you to keep your validation and business rules in one place (within your model layer), and avoid having it creep into your Controllers and Views.  Keeping the validation logic in the model layer helps ensure that you do not duplicate validation/business logic as you add more Controllers and Views to your application.  It allows you to quickly change your business rules/validation logic in one single place (within your model layer) – and have all controllers/views across your application immediately reflect it.  This help keep your application code clean and easily maintainable, and makes it much easier to evolve and update your application in the future. Summary EF Code First (starting with CTP5) now has built-in support for both DataAnnotations and the IValidatableObject interface.  This allows you to easily add validation and business rules to your models, and have EF automatically ensure that they are enforced anytime someone tries to persist changes of them to a database.  ASP.NET MVC 3 also now supports both DataAnnotations and IValidatableObject as well, which makes it even easier to use them with your EF Code First model layer – and then have the controllers/views within your web layer automatically honor and support them as well.  This makes it easy to build clean and highly maintainable applications. You don’t have to use DataAnnotations or IValidatableObject to perform your validation/business logic.  You can always roll your own custom validation architecture and/or use other more advanced validation frameworks/patterns if you want.  But for a lot of applications this built-in support will probably be sufficient – and provide a highly productive way to build solutions. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• What is the best database design and/or software to model a thesaurus?

  - by Miles O'Keefe

  I would like to design a web app that functions as a simple thesaurus : a long list of words with attributes, all of which are linked to each other. Wikipedia defines it as: In Information Science, Library Science, and Information Technology, specialized thesauri are designed for information retrieval. They are a type of controlled vocabulary, for indexing or tagging purposes. Such a thesaurus can be used as the basis of an index for online material. The Art and Architecture Thesaurus, for example, is used to index the Canadian Information retrieval thesauri are formally organized so that existing relationships between concepts are made explicit. What database software, design or model would best fit this? Are PHP and MySQL good technologies to handle it?

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• Has anyone used these database publish tools in Visual Studio 2012/2013 ?

  - by punkouter

  I am trying to figure out if they are actually useful... I have a DBProject and it would be nice if when I publish from my DEV to my TEST it what automatically copy the schema and data from DEV to TEST.. is that what this tab in visual studio is for ? On PROD I would never want to copy the data over but maybe I would change the schema and want to move that schema to PROD.. so is that what this tab is for ? For now we are using WEB DEPLOY but none of these database options.. We are manually using DATA COMPARE to sync changes on the various databases/DBproject... Any advice?

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• 2 Servers 1 Database - Can I use Redis?

  - by Aust

  Ok I have a couple of questions here. First let me give you some background information. I'm starting a project where I have a node.js server running my application and my website running on another normal server. My application will allow multiple users simultaneous connections and updates to the database so Redis seemed like a good fit there because of its speed and atomic functions. For someone to access my application they have to login with an account. To get an account, they have to signup for one through my website. So my website needs a database, but its not important to have a database like Redis here because it doesn't need it. Which leads me to my first question: 1. Can Redis even be used without node.js? It seems like it would be convenient if both of my servers were using the same database to keep track of information. In some cases, they will keep track of the same information (as in user information) and in other cases, they will be keeping track of separate information. So even if the website wouldn't be taking full advantage of all that Redis has to offer it seems like it would be more convenient. So assuming Redis could be used in this situation that leads to my next question: 2. Since Redis is linked with JavaScript, how would I handle the security from my website users? What would be stopping my website users from opening firebug or chrome's inspector and making changes to the database? Maybe if I designed my site with the layout like this: apply.php-update.php-home.php. Where after they submitted their form it would redirect them to the update page where the JavaScript would run and then redirect them after the database updated to the home page. I don't really know I'm just taking shots in the dark at this point. :) Maybe a better alternative would be to have my node.js application access its own Redis database and also have access to another MySQL database that my website also has access to. Or maybe there is another database that would be better suited for this situation other than Redis. Anyways any direction on this matter would be greatly appreciated. :)

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• SQL, moving million records from a database to other database [migrated]

  - by Ryoma

  I am a C# developer, I am not really good with SQL. I have a simple questions here. I need to move more than 50 millions records from a database to other database. I tried to use the import function in ms SQL, however it got stuck because the log was full (I got an error message The transaction log for database 'mydatabase' is full due to 'LOG_BACKUP'). The database recovery model was set to simple. My friend said that importing millions records using task-import data will cause the log to be massive and told me to use loop instead to transfer the data, does anyone know how and why? thanks in advance

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• SQL SERVER T-SQL Script to Take Database Offline Take Database Online

  Blog reader Joyesh Mitra recently left a comment to one of my very old posts about SQL SERVER 2005 Take Off Line or Detach Database, which I have written focusing on taking the database offline. However, I did not include how to bring the offline database to online in that post. The reason I [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Should each app have its own database, or should small apps be merged into one?

  - by King

  We have a bunch of small to medium sized apps, each of which has its own database (MSSQL Server). There was a suggestion that we consoldate the 'related' databases into a smaller set amount of larger databases. They don't particularly share a lot of data, they would just be under a similar business group. For example, using a 'Finance' DB to hold the tables and procedures for finance apps. Would it be appropriate to use a different schema for each app? E.g. App1.SomeTable App1.SomeOtherTable AppTwo.SomeTable What are the pros and cons of this approach? What should I watch out for? Thanks

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• PL/SQL Practices: First Things First

  Ask the right questions before starting construction of your new PL/SQL-based application.

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• How should I make searching a relational database more efficient?

  - by Travis J

  This is in the scope of a web application. I have a database which has a few nested relations. There is a feature which depicts the history of a large chain of relations. It is essentially a data analysis feature. The issue is that in order to search, a large object graph must be loaded - the loading time for this object graph is not quick enough to be viable. The problem is that without loading the whole graph it makes searching from a single string nearly impossible. In order to search, explicit fields must be specified and the search data supplied. Is there a design pattern for exposing the data in a way which facilitates a single string search instead of having to explicitly define parameters?

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• 3?????????????(Database??)

  - by rika.tokumichi

  ???????????OTN????????? ????GW????????????????????????????????????????????????????????? ???????????????????????????????????? ???Database??????????????3?????????????????????????????????? ??????????? 1?:Oracle SQL Developer 2.1 (2.1.0.63.73)?Download? 2?:Oracle Database 11g Release 1?Download? 3?:Oracle Database 10g Express Edition?Download? 4?:Oracle Database 10g Release 2?Download? 5?:Oracle Database 11g Release 2?Download? (????3?1?~3?31?) ??????????????···??????????????????????? ????????OS···· Oracle Database 11g Release 2 Windows? ????????????????????!! OTN??????!Windows??????????????????????????? ????????????????????????????????? >11g R2 on Windows???????! ???????? Microsoft Windows (32-bit) Microsoft Windows (x64) ???????????

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• Oracle Database 11.2.0.4 Certified with EBS on Microsoft Windows Server

  - by John Abraham

  As a follow up to to a previous announcement, Oracle Database 11g Release 2 (11.2.0.4) is now certified with Oracle E-Business Suite Release 11i and Release 12 on the following Microsoft Windows Server operating systems: Release 12.2 (12.2.3 and higher): Microsoft Windows x64 (64-bit) (2008 R2) Release 12.1 (12.1.1 and higher): Microsoft Windows Server (32-bit) (2003, 2008) Microsoft Windows x64 (64-bit) (20031, 20081, 2008 R22) Release 12.0 (12.0.4 and higher): Microsoft Windows Server (32-bit) (2003) Microsoft Windows x64 (64-bit) (2003, 2008, 2008 R2)1 Release 11i (11.5.10.2 + ATG PF.H RUP 6 and higher):: Microsoft Windows Server (32-bit) (2003, 20081) Microsoft Windows x64 (64-bit) (2003, 2008, 2008 R2)1 Notes: 1: This OS is a 'database tier only' or 'split tier configuration' platform where the application tier must be on a fully certified E-Business Suite platform. 2: This OS is a 'database tier only' platform for Release 11i. For 12.1.1 or higher, it is also supported on the application tier via the migration process outlined in My Oracle Support Document 1188535.1. This announcement for Oracle E-Business Suite 11i and R12 includes: Oracle Database 11gR2 version 11.2.0.4 Oracle Database 11gR2 version 11.2.0.4 Real Application Clusters (RAC) Oracle Database Vault 11gR2 version 11.2.0.4 Transparent Data Encryption (Column Encryption) using Oracle Database 11gR2 version 11.2.0.4 TDE Tablespace Encryption using Oracle Database 11gR2 version 11.2.0.4 Advanced Security Option (ASO)/Advanced Networking Option (ANO) with Oracle Database 11gR2 version 11.2.0.4 Export/Import Process for Oracle E-Business Suite Release 11i and Release 12 Database Instances Transportable Database and Transportable Tablespaces Data Migration Processes for Oracle E-Business Suite Release 11i and Release 12 Certification data in My Oracle Support (http://support.oracle.com) has been updated with this certification - please review the documents below for all requirements and additional details: Where can I find more information? MOS Document 881505.1 - Interoperability Notes - Oracle E-Business Suite Release 11i with Oracle Database 11g Release 2 (11.2.0) MOS Document 1058763.1 - Interoperability Notes - Oracle E-Business Suite Release 12 with Oracle Database 11g Release 2 (11.2.0) MOS Dcoument 1623879.1 - Interoperability Notes - Oracle E-Business Suite Release 12.2 with Oracle Database 11g Release 2 (11.2.0) MOS Document 1091086.1 - Integrating Oracle E-Business Suite Release 11i with Oracle Database Vault 11gR2 MOS Document 1091083.1 - Integrating Oracle E-Business Suite Release 12 with Oracle Database Vault 11gR2 MOS Document 216205.1 - Database Initialization Parameters for Oracle E-Business Suite 11i MOS Document 396009.1 - Database Initialization Parameters for Oracle Applications Release 12 MOS Document 823586.1 - Using Oracle 11g Release 2 Real Application Clusters with Oracle E-Business Suite Release 11i MOS Document 823587.1 - Using Oracle 11g Release 2 Real Application Clusters with Oracle E-Business Suite Release 12 MOS Document 946413.1 - Using Oracle Applications with a Split Configuration Database Tier on Oracle Release 11g Release 2 MOS Document 403294.1 - Using Transparent Data Encryption (TDE) Column Encryption with Oracle E-Business Suite Release 11i MOS Document 732764.1 - Using Transparent Data Encryption (TDE) Column Encryption with Oracle E-Business Suite Release 12 MOS Document 828223.1 - Using TDE Tablespace Encryption with Oracle E-Business Suite Release 11i MOS Document 828229.1 - Using TDE Tablespace Encryption with Oracle E-Business Suite Release 12 MOS Document 391248.1 - Encrypting Oracle E-Business Suite Release 11i Network Traffic using Advanced Security Option and Advanced Networking Option MOS Document 376700.1 - Enabling SSL in Oracle Application Release 12 MOS Document 732764.1 - Using Transparent Data Encryption (TDE) Column Encryption with Oracle E-Business Suite Release 12 MOS Document 557738.1 - Export/Import Process for Oracle E-Business Suite Release 11i Database Instances Using Oracle Database 11g Release 1 or 11g Release 2 MOS Document 741818.1 - Export/Import Process for Oracle E-Business Suite Release 12 Database Instances Using Oracle Database 11g Release 1 or 11g Release 2 MOS Document 1366265.1 - Using Transportable Tablespaces to Migrate Oracle Applications 11i Using Oracle Database 11g Release 2 MOS Document 1311487.1 - Using Transportable Tablespaces to Migrate Oracle E-Business Suite Release 12 Using Oracle Database 11g Release 2 MOS Document 729309.1 - Using Transportable Database to Migrate Oracle E-Business Suite Release 11i Using Oracle Database 10g Release 2 or 11g MOS Document 734763.1 - Using Transportable Database to Migrate Oracle E-Business Suite Release 12 Using Oracle Database 10g Release 2 or 11g MOS Document 1188535.1 - Migrating Oracle E-Business Suite R12 to Microsoft Windows Server 2008 R2 MOS Dcoument 1349240.1 - Database Preparation Guidelines for an Oracle E-Business Suite Release 12.2 Upgrade MOS Document 1594274.1 - Oracle E-Business Suite Release 12.2: Consolidated List of Patches and Technology Bug Fixes Please also review the platform-specific Oracle Database Installation Guides for operating system and other prerequisites.

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• [EF 4 POCO] Problem with INSERT...

  - by Darmak

  Hi all, I'm so frustrated because of this problem, you have no idea... I have 2 classes: Post and Comment. I use EF 4 POCO support, I don't have foreign key columns in my .edmx model (Comment class doesn't have PostID property, but has Post property) class Comment { public Post post { get; set; } // ... } class Post { public virtual ICollection<Comment> Comments { get; set; } // ... } Can someone tell me why the code below doesn't work? I want to create a new comment for a post: Comment comm = context.CreateObject<Comment>(); Post post = context.Posts.Where(p => p.Slug == "something").SingleOrDefault(); // post != null, so don't worry, be happy // here I set all other comm properties and... comm.Post = post; context.AddObject("Comments", comm); // Exception here context.SaveChanges(); The Exception is: Cannot insert the value NULL into column 'PostID', table 'Blog.Comments'; column does not allow nulls. INSERT fails. ... this 'PostID' column is of course a foreign key to the Posts table. Any help will be appreciated!

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• Server configurations for hosting MySQL database

  - by shyam

  I have a web application which uses a MySQL database hosted on a virtual server. I've been using this server when I started the application and when the database was really small. Now it has grown and the server is not able to handle the db, causing frequent db errors. I'm planning to get a server and I need suggestions for that. Like I said, the db is now 9 GB, and is growing considerably fast. There are a number of tables with millions of rows, which are frequently updated and queried. The most frequent error the db shows is Lock wait timeout exceeded. Previously there used to be "The total number of locks exceeds the lock table size" errors too, but I could avoid it by increasing Innodb buffer pool size. Please suggest what configurations should I look for in the server I should buy. I read somewhere that the db should ideally have a buffer pool size greater than the size of its data, so in my case I guess I'd need memory gt 9 GB. What other things should I look for in the server? Just tell me if I should give you more info about the

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• Recover mysql database - mysqldump gives "table <tablename> doesn't exist (1146)"

  - by Matthew

  Backstory Ubuntu died (wouldn't boot) and I couldn't fix it. I booted a live cd to recover the important stuff and saved it to my NAS. One of the things I backed up was /var/lib/mysql. Reinstalled with Linux Mint because I was on Ubuntu 10.0.4 this was a good opportunity to try a new distro (and I don't like Unity). Now I want to recover my old mediawiki, so I shut down mysql daemon, cp -R /media/NAS/Backup/mysql/mediawiki@002d1_19_1 /var/lib/mysql/, set file ownership and permissions correctly, and start mysql back up. Problem Now I'm trying to export the database so I can restore the database, but when I execute the mysqldump I get an error: $ mysqldump -u mediawikiuser -p mediawiki-1_19_1 -c | gzip -9 > wiki.2012-11-15.sql.gz Enter password: mysqldump: Got error: 1146: Table 'mediawiki-1_19_1.archive' doesn't exist when using LOCK TABLES Things I've tried I tried using --skip-lock-tables but I get this: Error: Couldn't read status information for table archive () mysqldump: Couldn't execute 'show create table `archive`': Table 'mediawiki-1_19_1.archive' doesn't exist (1146) I tried logging in to mysql and I can list the tables that should be there, but trying to describe or select from them errors out the same way as the dump: mysql> show tables; +----------------------------+ | Tables_in_mediawiki-1_19_1 | +----------------------------+ | archive | | category | | categorylinks | ... | user_properties | | valid_tag | | watchlist | +----------------------------+ 49 rows in set (0.00 sec) mysql> describe archive; ERROR 1146 (42S02): Table 'mediawiki-1_19_1.archive' doesn't exist I believe mediawiki was installed using innodb and binary data. Am I screwed or is there a way to recover this?

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• Database types for customer analytics

  - by Drewdavid

  I am exploring a paid solution to start providing better embedded, dashboard-style analytics information to our website customers/account holders, but would like to also offer an in-house development option to our team. The more equipped I am with specifics (such as the subject of this question), the better the adoption rate from the team (or so I have found), regardless of the path we choose Would anyone care to summarize a couple of options for a fast and scalable database type through which we would provide the following: • Daily pageviews to a users account pages (users have between 1 and 1000 pages) • Some calculated/compounded metrics (such as conversion rate, i.e. certain page type viewed to contact form thank you page ratio) • We have about 1,500 members (will need room to grow); the number of concurrently logged in users will for the question's sake be 50 I ask because our developer has balked at providing this level of "over time" granularity (i.e. daily) due to the number of space it would take up in a MYSQL database To avoid a downvote I have asked specifically for more than one option, realizing that different people will have different solutions. I will make amendments to my question if so guided by answering parties Thank you for sharing your valued answers :)

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• How to conciliate OOAD and Database Design?

  - by user1620696

  Recently I've studied about object oriented analysis and design and I liked a lot about it. In every place I've read people say that the idea is to start with the minimum set of requirements and go improving along the way, revisiting this each iteration and making it better as we contiuously develop and contact the customer interested in the software. In particular, one course from Lynda.com said a lot of that: we don't want to spend a lot of time planing everything upfront, we just want to have the minimum to get started and then improve this each iteration. Now, I've also seem a course from the same guy about database design, and there he says differently. He says that although when working with object orientation he likes the agile iterative approach, for database design we should really spend a lot of time planing things upfront instead of just going along the way with the minimum. But this confuses me a little. Indeed, the database will persist important data from our domain model and perhaps configurations of the software and so on. Now, if I'm going to continuously revist the analysis and design of the model, it seems the database design should change also. In the same way, if we plan all the database upfront it seems we are also planing all the model upfront, so the two ideas seems to be incompatible. I really like agile iterative approach, but I'm also looking at getting better design for the database also, so when working with agile iterative approach, how should we deal with the database design?

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• Implementation details of database synchronisation API

  - by Daniel

  I want to achieve a database synchronisation between my server database and a client application. The server would run MySQL and the applications may run different database technologies, their implementation isn't important. I have a MySQL database online and web accessible via an API I wrote in PHP (just a detail). My client application ships with a copy of the online data. As time passes my goal is to check for any changes in the online database and make these updates available to the client app via an API call, by sending a date to an API endpoint corresponding to the last date the app was updated, the response would be a JSON filled with all new objects and updated objects, and delete IDs, this makes possible to update the local store appropriately. Essentially I want to do this: http://dbconvert.com/synchronization.php My question is about the implementation details. Would I need to add a column to my database tables with a "last modified" date? Since the client app could be very out of date if it's been offline for a long time, does that also mean I shouldn't delete data from the online database but instead have another column called "delete" set to 1 and a modified date updated appropriately? Would my SQL query simply check for all data with a modified date superior then the date passed into the API request by the client? I feel like there's a lot more to it then having a ton of dates everywhere. And also, worry that I will need to persist a lot of old data in order to ensure that old versions of the client app always have the opportunity to delete parts of their data when they are able to sync.

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• Oracle Database 12c is Generally Available

  - by Thanos

  Oracle Database 12c, a major release of Oracle’s flagship product, is generally available as of 25 June 2013. Oracle Database 12c introduces a breakthrough, new multitenant architecture enabling customers to create multiple, pluggable databases for database consolidation and cloud deployments. Customers will realize greater efficiency and flexibility through innovations such as Oracle Multitenant option and Automatic Data Optimization with Heat Map, for compressing and tiering data at a higher density. These unique advancements, combined with major enhancements in availability, security, and big data support, make Oracle Database 12c the ideal platform for private and public cloud deployments. As of 25/06/2013, the product is available for download on Linux x86-64, Solaris Sparc64 and Solaris (x86-64) via Oracle Technology Network. A news release is planned for July 1st, and an external launch webcast, Plug into the Cloud with Oracle Database 12c, featuring Mark Hurd, Andy Mendelsohn, Tom Kyte and other experts is planned for July 10th. Open here in New Window Everybody can register for the launch webcast here and register to attend global in-person events here. Resources: www.oracle.com/database www.oracle.com/databaseoptions Oracle Partner Network Database Knowledge Zone Open in Google Docs Viewer Open link in new tab Open link in new window Open link in new incognito window Download file Copy link address Edit PDF File on PDFescape.com

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• Enterprise Manager Database Control Configuration - Recovering From Errors Due to CA Expiry on Oracle Database 10.2.0.4 or 10.2.0.5 from 31-Dec-2010 onwards

  - by jayatheertha.rao(at)oracle.com

  Description What is the Issue? In Enterprise Manager Database Control with Oracle Database 10.2.0.4 and 10.2.0.5, the root certificate used to secure communications via the Secure Socket Layer (SSL) protocol will expire on 31-Dec-2010 00:00:00. The certificate expiration will cause errors if you attempt to configure Database Control on or after 31-Dec-2010. Existing Database Control configurations are not affected by this issue. Likelihood of Occurrence What Versions Are Affected? The issue impacts configuration of Database Control with Oracle Database 10.2.0.4 and 10.2.0.5 only. It does not impact database creation or upgrade. The issue does not impact existing Database Control configurations. What Happens During Database Control Configuration Failure? Database Configuration Assistant (DBCA) and Database Upgrade Assistant (DBUA) Errors Database Configuration Assistant (DBCA) and Database Upgrade Assistant (DBUA) will report the following error in the console: Could not complete the Enterprise Manager configuration.Enterprise manager configuration failed due to the following error -Error starting Database Control Enterprise Manager Configuration Assistant (EMCA) Errors Enterprise Manager Configuration Assistant (EMCA) will write errors similar to those below to the emca.log file: CONFIG: Securing Database Control completed successfully .Jan 2, 2011 7:22:47 PM oracle.sysman.emcp.ParamsManager getParamCONFIG: No value was set for the parameter ORACLE_HOSTNAME.Jan 2, 2011 7:22:47 PM oracle.sysman.emcp.util.DBControlUtil startOMSINFO: Starting Database Control (this may take a while) ...Jan 2, 2011 7:22:47 PM oracle.sysman.emcp.util.PlatformInterface addEnvVarToListCONFIG: Value for env var 'ORACLE_HOSTNAME' is '', discarding the sameCONFIG: Returning env array from cacheJan 2, 2011 7:22:47 PM oracle.sysman.emcp.util.PlatformInterface executeCommandCONFIG: Starting execution: /myhost/bin/emctl start dbconsoleJan 2, 2011 7:27:26 PM oracle.sysman.emcp.util.PlatformInterface executeCommandCONFIG: Exit value of 1Jan 2, 2011 7:27:26 PM oracle.sysman.emcp.util.PlatformInterface executeCommandCONFIG: Oracle Enterprise Manager 10g Database Control Release 10.2.0.4.0Copyright (c) 1996, 2007 Oracle Corporation. All rights reserved.https://myhost:5501/em/console/aboutApplicationStarting Oracle Enterprise Manager 10g Database Control............................................................................................. failed.------------------------------------------------------------------Logs are generated in directory /myhost/sysman/logJan 2, 2011 7:27:26 PM oracle.sysman.emcp.util.PlatformInterface executeCommandWARNING: Error executing /myhost/bin/emctl start dbconsoleJan 2, 2011 7:27:26 PM oracle.sysman.emcp.EMConfig performSEVERE: Error starting Database ControlRefer to the log file at /myhost/dbua/d4/upgrade/emConfig.log for more details.Jan 2, 2011 7:27:26 PM oracle.sysman.emcp.EMConfig performCONFIG: Stack Trace:oracle.sysman.emcp.exception.EMConfigException: Error starting Database Controlat oracle.sysman.emcp.EMDBPostConfig.performUpgrade(EMDBPostConfig.java:763)at oracle.sysman.emcp.EMDBPostConfig.invoke(EMDBPostConfig.java:232)at oracle.sysman.emcp.EMDBPostConfig.invoke(EMDBPostConfig.java:193)at oracle.sysman.emcp.EMConfig.perform(EMConfig.java:184)at oracle.sysman.assistants.util.em.EMConfiguration.run(EMConfiguration.java:436)at oracle.sysman.assistants.util.em.EMConfigStep.executeImpl(EMConfigStep.java:140)at oracle.sysman.assistants.util.step.BasicStep.execute(BasicStep.java:210)at oracle.sysman.assistants.util.step.BasicStep.callStep(BasicStep.java:251)at oracle.sysman.assistants.dbma.backend.EMConfigStep.executeStepImpl(EMConfigStep.java:104)at oracle.sysman.assistants.dbma.backend.SummarizableStep.executeImpl(SummarizableStep.java:175)at oracle.sysman.assistants.util.step.BasicStep.execute(BasicStep.java:210)at oracle.sysman.assistants.util.step.Step.execute(Step.java:140)at oracle.sysman.assistants.util.step.StepContext$ModeRunner.run(StepContext.java:2488)at java.lang.Thread.run(Thread.java:534) The EMCA console will display output similar to the following: aime@myhost09 db_1]$ bin/emca -config dbcontrol db -repos recreate -clusterSTARTED EMCA at Jan 11, 2011 4:11:01 PMEM Configuration Assistant, Version 10.2.0.1.0 ProductionCopyright (c) 2003, 2005, Oracle. All rights reserved.Enter the following information:Database unique name: catestDatabase Control is already configured for the database catestYou have chosen to configure Database Control for managing the database catestThis will remove the existing configuration and the default settings and perform a fresh configurationDo you wish to continue? [yes(Y)/no(N)]: YListener port number: 1521Cluster name: myclusterPassword for SYS user:Password for DBSNMP user:Password for SYSMAN user:Email address for notifications (optional):Outgoing Mail (SMTP) server for notifications (optional):........Jan 11, 2011 4:18:05 PM oracle.sysman.emcp.util.DBControlUtil secureDBConsoleINFO: Securing Database Control (this may take a while) ...Jan 11, 2011 4:19:31 PM oracle.sysman.emcp.util.DBControlUtil startOMSINFO: Starting Database Control (this may take a while) ...Jan 11, 2011 4:28:38 PM oracle.sysman.emcp.EMConfig performSEVERE: Error starting Database ControlRefer to the log file at /myhost/oracle/product/10.2.0/db_1/cfgtoollogs/emca/catest/emca_2011-01-11_04-11-01-PM.log for more details.Could not complete the configuration. Refer to the log file at /myhost/oracle/product/10.2.0/db_1/cfgtoollogs/emca/catest/emca_2011-01-11_04-11-01-PM.log for more details. At the end of the database installation on non-Windows platforms, both Database Control and the Management Agent will be up and running, even though the status of both components will be shown as not running, because EMCTL will be unable to connect to the dbconsole process. In addition, Database Control will fail to connect to the Agent. Note for Windows Platform Only:On Windows, the dbconsole process will be stopped after the failed configuration attempt. Note that the tool used to perform Database Control configuration (DBUA, DBCA or EMCA) will also wait for 15 minutes for Database Control to start, then time out. The output of the "emctl status dbconsole" command incorrectly returns the status of Database Control, as shown below: $ ./emctl status dbconsoleOracle Enterprise Manager 10g Database Control Release 10.2.0.1.0Copyright (c) 1996, 2005 Oracle Corporation. All rights reserved.https://myhost:1158/em/console/aboutApplicationOracle Enterprise Manager 10g is not running. The output of the "emctl status agent" command incorrectly returns the status of the Agent, as shownbelow: $ ./emctl status agentOracle Enterprise Manager 10g Database Control Release 10.2.0.1.0Copyright (c) 1996, 2005 Oracle Corporation. All rights reserved.---------------------------------------------------------------Agent is Not Running   For Solution, refer to Note: 1222603.1 Note: 1217493.1

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• Upgrading to Code Based Migrations EF 4.3.1 with Connector/Net 6.6

  - by GABMARTINEZ

  Entity Framework 4.3.1 includes a new feature called code first migrations.  We are adding support for this feature in our upcoming 6.6 release of Connector/Net.  In this walk-through we'll see the workflow of code-based migrations when you have an existing application and you would like to upgrade to this EF 4.3.1 version and use this approach, so you can keep track of the changes that you do to your database.   The first thing we need to do is add the new Entity Framework 4.3.1 package to our application. This should via the NuGet package manager.  You can read more about why EF is not part of the .NET framework here. Adding EF 4.3.1 to our existing application  Inside VS 2010 go to Tools -> Library Package Manager -> Package Manager Console, this will open the Power Shell Host Window where we can work with all the EF commands. In order to install this library to your existing application you should type Install-Package EntityFramework This will make some changes to your application. So Let's check them. In your .config file you'll see a  <configSections> which contains the version you have from EntityFramework and also was added the <entityFramework> section as shown below. This section is by default configured to use SQL Express which won't be necesary for this case. So you can comment it out or leave it empty. Also please make sure you're using the Connector/Net 6.6.x version which is the one that has this support as is shown in the previous image. At this point we face one issue; in order to be able to work with Migrations we need the __MigrationHistory table that we don't have yet since our Database was created with an older version. This table is used to keep track of the changes in our model. So we need to get it in our existing Database. Getting a Migration-History table into an existing database First thing we need to do to enable migrations in our existing application is to create our configuration class which will set up the MySqlClient Provider as our SQL Generator. So we have to add it with the following code: using System.Data.Entity.Migrations;     //add this at the top of your cs file public class Configuration : DbMigrationsConfiguration<NameOfYourDbContext>  //Make sure to use the name of your existing DBContext { public Configuration() { this.AutomaticMigrationsEnabled = false; //Set Automatic migrations to false since we'll be applying the migrations manually for this case. SetSqlGenerator("MySql.Data.MySqlClient", new MySql.Data.Entity.MySqlMigrationSqlGenerator());     }   }  This code will set up our configuration that we'll be using when executing all the migrations for our application. Once we have done this we can Build our application so we can check that everything is fine. Creating our Initial Migration Now let's add our Initial Migration. In Package Manager Console, execute "add-migration InitialCreate", you can use any other name but I like to set this as our initial create for future reference. After we run this command, some changes were done in our application: A new Migrations Folder was created. A new class migration call InitialCreate which in most of the cases should have empty Up and Down methods as long as your database is up to date with your Model. Since all your entities already exists, delete all duplicated code to create any entity which exists already in your Database if there is any. I found this easier when you don't have any pending updates to do to your database. Now we have our empty migration that will make no changes in our database and represents how are all the things at the begining of our migrations.  Finally, let's create our MigrationsHistory table. Optionally you can add SQL code to delete the edmdata table which is not needed anymore. public override void Up() { // Just make sure that you used 4.1 or later version         Sql("DROP TABLE EdmMetadata"); } From our Package Manager Console let's type: Update-database; If you like to see the operations made on each Update-database command you can use the flag -verbose after the Update-database. This will make two important changes.  It will execute the Up method in the initial migration which has no changes in the database. And second, and very important,  it will create the __MigrationHistory table necessary to keep track of your changes. And next time you make a change to your database it will compare the current model to the one stored in the Model Column of this table. Conclusion The important thing of this walk through is that we must create our initial migration before we start doing any changes to our model. This way we'll be adding the necessary __MigrationsHistory table to our existing database, so we can keep our database up to date with all the changes we do in our context model using migrations. Hope you have found this information useful. Please let us know if you have any questions or comments, also please check our forums here where we keep answering questions in general for the community.  Happy MySQL/Net Coding!

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