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When you purchase a book from an online bookstore, you exchange money (in the form of credit) for a book. If your credit is good, a series of related operations ensure that you get the books, and the bookstore gets your money. However, if a single operation in the series fails during the exchange, the entire exchange fails. You do not get the book and the bookstore does not get your money.

The technology responsible for making the exchange balanced and predictable is called transaction processing.

ii. Identify and explain ANY TWO subsystems under EACH of the three TPS identified above (12 marks)