Performing Nested Transactions using Savepoints in Oracle Data Provider for .NET (ODP.NET)

Table of Contents

Objective of the Sample Application
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The purpose of this sample is to demonstrate how Nested Transactions can be achieved using Savepoint feature in ODP.NET. 

The Savepoint feature provides fine-grained control of transactions by marking the intermediate points within the transaction. Once the Savepoint has been set, the transaction can be rolled back to that Savepoint without affecting the preceding work. Through OracleTransaction class provided in Oracle.DataAccess.ClientNamespace with ODP.NET, the rollback operation to a particular Savepoint can be done. 

Overview of the Sample Application
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Using a C# console application, this sample demonstrates: 
  • How to create Savepoints in a transaction
  • How to rollback upto a particular Savepoint in a transaction
  • How to commit/rollback a transaction
When this sample is run, a database transaction begins. The sample inserts a row in the Products table before creating any Savepoints. Then three other rows are inserted in Products table. Before inserting each of the three rows, a Savepoint is created. The user is displayed the names of all Savepoint created. The user is given an option to rollback to a particular Savepoint. The user can provide a Savepoint name that he wishes to rollback. After rolling back to a particular Savepoint, the user can further rollback to other Savepoints (if any) or commit the data or rollback completely.This completes the transaction. Hence it demonstrates how Nested Transactions are performed using Savepoints in ODP.NET.

User Notes with Screen Shots
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1. When this sample is run, a console application as shown in Figure 1.1 is displayed. A transaction is started and data for Product 1 is inserted.The Savepoints "a", "b" and "c" are created before inserting data for Product 2, Product 3 and Product 4 respectively.

Figure 1.1 Displays the initial screen

2. The user can input the savepoint name upto which he wishes to rollback the transaction. For eg. If the user inputs "b" savepoint then the DML operations upto Savepoint "b" i.e. Insert operations for Product 3, Product 4 gets rolled back. The message on console is displayed as shown in Figure 1.2. 

Figure 1.2 Displays user the options for rolling back to a savepoint, commit, rollback completely

3. The user can further commit the changes or rollback to the remaining savepoint (if any), in the above example the user can rollback to savepoint "a" or rollback completely.

Required Software 
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  • Visual C# installed with MS Development Environment 7.0 version (MS Visual Studio .NET)  including MS .NET Framework 1.0 version 
  • Oracle8i Database or later running SQL*Net TCP/IP listener (can be downloaded here) 
  • Oracle Data Provider for .NET (ODP.NET) (can be downloaded here) 

Extracting the Sample
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Unzip SavepointSample.zipusing Winzip or command utility to your convenient directory. Extraction of the zip file results  in the creation of Savepoint directory. 
 
 

Database Setup 
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Connect to your database as any user and run the script Savepoint\Setup\DatabaseSetup.sql at the SQL prompt. 

@<Extract_Dir>\Savepoint\Setup\DatabaseSetup.sql 

where <Extract_Dir> is the directory where you have extracted the sample. 

The script creates an user "OraNet" with password "OraNet". 

It creates PRODUCTS table. This table is not populated with any initial data. 

Preparing and Running the Sample
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1.Ensure that the Database setup has been completed. 

2.Open Savepoint.sln using Visual Studio .NET from <Extract_Dir>\Savepoint folder. 

3.Edit ConnectionParams.cs file to change the database connection parameters i.e.TNSName for database you want to use . Save this file. 

4.Ensure that the following .NET Component References have been added to Savepoint project: 

  • System 
  • System.Data
  • Oracle.DataAccess.
To add the above .NET Components 
  • Go to Menu ->View-> Solution Explorer.
  • Right click on Savepoint project, choose 'Add Reference'.
  • Choose the above .NET Components from the list displayed.
  • Click 'Select', then OK.
  • The chosen .NET component gets added to the project. 
5. Build and run the sample.
 

Description of Sample Files 
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Directory File Name Description
Savepoint\doc Readme.html This file
blaf.css This is a cascading style sheet applied to Readme.html
Savepoint\doc\images *.gif This folder contains images used as screenshots in the Readme.html file.
Savepoint\src\ ConnectionParams.cs This C# file manages the database connection used by sample.
Savepoint.cs This C# file contains source code for all methods used for creating Savepoints and  rollback/commit operations.
Savepoint.csproj C# project file
Savepoint.csproj.user Visual Studio Project User Options (this file gets automatically generated when a Visual Studio Project is created)
Savepoint.sln Visual Studio Solution
Savepoint\Setup DatabaseSetup.sql This is a SQL script file 

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