Serialization
The goal of a complete concurrency solution is to provide the highest level of isolation between the actions of different users accessing the same data. As defined by the SQL92 standard, this highest level is called serializable. As the name implies, serializable transactions appear as though they have been executed in a series of distinct, ordered transactions. When one transaction begins, it is isolated from any changes that occur to its data from subsequent transactions.
To the user, a serializable transaction looks as though it has the exclusive use of the database for the duration of the transaction. Serializable transaction are predictable and reproducible, the two cardinal virtues of data integrity.
Of course, it is nontrivial to have a database server support thousands of users and have each user think that she is the only one. But MVRC in Oracle enables this feat.