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DEFINITION
Transaction processing is the unambiguous and independent execution of a set of operations on data in a relational database, which treats that set of actions as a single event. If any part of the transaction process fails, the entire transaction fails and all participating resources are rolled back to their previous state.
YIN AND YANG, life and death, Clark Kent and Superman. Some concepts are so intertwined that it's impossible to imagine one without the other. Transaction processing (TP) and relational databases [Technology QuickStudy, Jan. 81 make up another such pairing.
In theory, TP can happen without a relational database, but you wouldn't want to try it. And you could do a relational database without TP, but you would lose one of the benefits of having a relational database: the ability to update multiple tables to reflect the completion of a transaction.
Systems capable of doing TP must pass the ACID test: atomicity, consistency, isolation and durability. Transactions are atomic, meaning they either happen or not. If one account is debited, some other account must be credited.
The TP system must always be consistent with its own rules. No transaction can happen if errors are returned as the transaction is processed. For example, if a table that must be updated is on a hard drive that is inaccessible, the transaction fails.
Isolating transactions means that other processes never see database tables in an intermediate state. They may get to see what the database looked like before or after the...