Explain what the concept of a transaction schema in a database is.

A transaction schema in a database is a set of rules and mechanisms that ensure data integrity and consistency during operations.

A transaction is a sequence of operations that must be completed entirely or not at all (atomicity). The main properties of transactions are described by the acronym ACID:

• Atomicity: all operations of a transaction are executed as a single unit.
• Consistency: after a transaction, the database remains in a correct state.
• Isolation: parallel transactions do not affect each other.
• Durability: changes confirmed by a transaction are saved even in case of failures.

Example: when transferring money between accounts, a transaction guarantees that the debit from one account and the credit to another will happen together or not at all.