Question - What is a transaction in ADO.NET? Explain the types of transactions available in ADO.NET.
Answer -
In ADO.NET, transactions are used when you want to bind several tasks together and execute them in the form of a single unit. The transaction provides data consistency by ensuring either all of the database operations will be succeeded or all of them will be failed. For example, consider an application that performs two tasks. First, it updates an item_order table with order information. Second, it updates an item_inventory table that holds inventory information, where a number of items ordered will be debited. If any one of the tasks fails, then both updates must be rolled back.
Two types of transactions supported by ADO.NET are as follows:
Local Transaction:
- A local transaction is a single-phase transaction that is directly handled by the database. Every .NET Framework data provider has its own Transaction object for bringing out local transactions.
- For example, if we want to perform a transaction using SQL Server database, we import a System.Data.SqlClient namespace. Similarly, to perform an Oracle transaction, import the System.Data.OracleClient namespace. A DbTransaction class will be used for writing code that is independent of the provider and that requires transactions.
Distributed Transaction:
- A distributed transaction is coordinated by a transaction monitor and will make use of fail-safe mechanisms like two-phase commit for transaction resolution. This transaction will affect multiple resources.
- If the user can make use of a distributed transaction, if he wants to do a transaction across multiple data servers such as Oracle, SQL Server, etc.
- If you want a distributed transaction to commit, all participants must guarantee that data modification made will be permanent. Changes must remain unchanged even if the system crash or other unforeseen events occur. Even if a single participant will make this guarantee fail, then the entire transaction will fail, and updates made to data within the transaction scope are rolled back.