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Boundaries of Transactions

In the database world a (new) transaction is begun (implicitly) after a commit or after a rollback. The commit or the rollback may be performed explicitly (using a COMMIT or a ROLLBACK statement) or implicitly by the system when a program terminates,^4.5where a commit is performed on successful termination and a rollback otherwise. There are no explicit BEGINs or ENDs to outline database transactions, and database transactions cannot be nested.

In connection with a file system transactions have to be outlined explicitly, because transactions are not a natural part of the system. Begins, ends, and probably also new transactional operations need to be introduced, so that the system can be told which operations belong to which transactions, and when the transactions are begun and ended.

Footnotes

... terminates,^4.5

The "program terminates" should not be taken literally, it could be at termination of any sequence of operations.

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