A more complicated example might be to delete a member of staff from the database and
to reassign the properties that he or she managed to another member of staff. In this case,
there is more than one change to be made to the database. If the transaction fails during
execution, perhaps because of a computer crash, the database will be in an inconsistent
state: some changes will have been made and others not. Consequently, the changes that
have been made will have to be undone to return the database to a consistent state again.
We discuss transaction support in Section 20.1.