Question

I wonder a case. I have a project using a database (Oracle and Mssql). My project has a framework that I manage transactions.
In thread I open a database connection and start a transaction.(In transaction, there are many update and insert queries.) While code is running, somehow connection is closed. Because I have try-catch block, I catch exception and rollback transaction. BUT; if my connection is closed because some reasons, how rollback query can run on database? How can I handle this situation? If I open a new connection and rollback, does it work?

Thanks.

Answer 1

There is a term you should know – ACID compliancy:

• Atomicity is an all-or-none proposition;
• Consistency guarantees that a transaction never leaves your database in a half-finished state.
• Isolation keeps transactions separated from each other until they’re finished.
• Durability guarantees that the database will keep track of pending changes in such a way that the server can recover from an abnormal termination.

Concerning MySQL

In order to get this at MySQL, you have to use Transaction Safe Tables (TST). Advantages of Transaction-Safe Tables:

• Safer. Even if MySQL crashes or you get hardware problems, you can get your data back, either by automatic recovery or from a backup + the transaction log.
• You can combine many statements and accept these all in one go with the COMMIT command.
• You can execute ROLLBACK to ignore your changes (if you are not running in auto-commit mode).
• If an update fails, all your changes will be restored.

Concerning SQL Server

You should read “Transaction Behavior On Lost Connection” MSDN forum topic.
To understand better what lays behind MS SQL Server transactions, read a good article “Locks and Duration of Transactions in MS SQL Server“