what is transaction?

• Lesson6 Transactions

http://www.youtube.com/watch?v=r_jhKrpDD5c&feature=channel&list=UL

• transaction

In computer programming, a transaction usually means a sequence of information exchange and related work (such as database updating) that is treated as a unit for the purposes of satisfying a request and for ensuring database integrity.

A typical transaction is a catalog merchandise order phoned in by a customer and entered into a computer by a customer representative. The order transaction involves checking an inventory database, confirming that the item is available, placing the order, and confirming that the order has been placed and the expected time of shipment. If we view this as a single transaction, then all of the steps must be completed before the transaction is successful and the database is actually changed to reflect the new order. If something happens before the transaction is successfully completed, any changes to the database must be kept track of so that they can be undone.
http://searchcio.techtarget.com/definition/transaction

• What Is a Transaction Processing System?

Transaction processing system is a program or software that processes all transactions that go in and out of a business or a company.
The system goes over the transactions one by one, like in an automated teller machine (ATM) that permits only one user at a time
The term “transaction,” in this case, does not only refer to financial aspects, but to requests for information as a whole, such as booking a flight or just logging into an online bank account.

In direct contrast to a transaction processing system is a batch processing system.
This system processes multiple transactions—or a “batch” of transactions—simultaneously.
The main disadvantage is that the processed transactions do not return immediate results.

A modern analogy is a torrent file connected to a folder of files.
The user cannot immediately access a file until all the files in the folder are completely downloaded.
http://www.wisegeek.com/what-is-a-transaction-processing-system.htm