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While doing certain modification in the database some time you need to lock the data so that no one can else perform modification in that data.There are two commonly known approaches for locking database they are optimistic locking and pessimistic locking.Both these approaches are used to maintain concurrency in the database.Pessimistic concurrency locking is done at rows of the data source to prevent users from modifying data in a way that affects other users.In this sample, all the work is done inside the event handlers for the two buttons, cmd Fill and cmd Update. Because you have set an isolation level for the transaction of Repeatable Read, which locks all records returned by the query, no other application will be able to update the data you retrieve. The second instance will simply display an error message, indicating it was chosen as the victim of a deadlock situation.First, add the following code for cmd Fill’s Click event handler: Dim txn As Sql Transaction Private Sub cmd Fill_Click(By Val sender As System. The next step is to create the update code, which commits the transaction and removes the record locks. You can also launch the application, click the Fill button, and then attempt to make a change to a record using another method, such as the SQL Server Query Analyzer.

Now a days browser based application is very common and having pessimistic locking is not a practical solution. NET: A transaction is an abstract unit of concurrent computation that execute automatically.The effect of transaction does not interfere with other transactions that access the same data.Also a transaction happens with all of its effects (In this case you will commit the changes) or it doesn’t happen none of its effects (In this case you will rollback the changes).if thiers is a way to cancel after update this would work.I am getting this message when I try to update my database table: Updating is not supported by data source 'Sql Data Source1' unless Update Command is specified I am new user of 2005 using visual studio with little knowlwdge of visual basic. I do not know why but it it seem like I have a protection on my data base like I can not modify it.Under no circumstances should you hold the transaction open while awaiting some action from the user, like I did for reasons of clarity in the sample application I presented.A user could easily walk away from the computer in the middle of an update, possibly leaving the records locked for hours or even days.In the main code I have specified code to write all those rows in which error has occurred during modification. Generate a Data Set, name it ds Customers, and add it to the designer window. You then set the Select Command’s Transaction property to the Transaction object you just created and call the Fill method to fill the Ds Customers1 Data Set. Return to the first instance of the application, change the same record by editing a different field, and click the Update button.Let’s explore these steps with a sample application. Finally, bind the Data Grid’s Data Source property to Ds Customers1. Add the event handlers Supporting pessimistic locking requires surprisingly little code. The Fill method will run the Select Command query you specified when you built the Data Adapter and will start the transaction on the server. The update made in the first instance of the application will succeed because it was holding a lock on the records.While updating modified data in the database if any of the concurrency conflict occur it raises Exception, which sets Data Row’s Has Error Boolean value. Close() End Sub Here, you take the Transaction object you created in cmd Fill_Click, txn, and assign it to the Insert Command, Update Command, and Delete Command properties of the Data Adapter.This we can easily handle with Data Adaptor event and with our own programming logic. This way, any changes made to the data will play back in the same transaction you started when you retrieved the records.

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  1. Posts about 1. Optimistic & Pessimistic locking written by arrao4u. In pessimistic locking when user wants to update data it locks the record and till then no one.

  2. Toolkit Reference for the Microsoft Deployment Toolkit. 09/09/2016; 485 minutes to read; Contributors. In this article. This reference is part of Microsoft.

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