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The concept of transactions has its origins in database systems (see [5, Ch.16], [47, Ch.6.9]). A transaction is a collection of operations that form a (single) logical unit of work. The classic example of a (database) transaction is the transferring of a certain amount of money from one bank account to another, see Appendix B. The essential idea of a transaction is atomicity, i.e., either all the operations of the transaction are performed or none of them are performed (there is no middle way).4.1

In the following sections I will look at properties of transactions and their implications (Section 4.1) especially with regards to mobility, and how they can be implemented (Section 4.2).


... way).4.1
That a transaction is atomic must not be understood as if it in some sense is the smallest unit, i.e., that it does not consist of distinguishable parts (operations).