The multiuser database management system's concern is how to control concurrency, which is the concurrent ACCESS of the same data by multiple USERS. Without SUFFICIENT concurrency controls, data could be updated or changed improperly, trading off with data integrity. To manage data concurrency is to make each user wait for a turn.
The goal of a database management system is to decrease the waiting time so it is either nonexistent or negligible to each user. The data manipulation language statements should proceed with as little intervention as possible, and destructive interactions among concurrent transactions should be prevented.
Destructive interaction is any interaction that updates data or alters UNDERLYING data structures INCORRECTLY. Neither performance nor data integrity can be sacrificed. Oracle solves such problems by using various types of locks and a multi-version consistency model.

The multiuser database management system's concern is how to control concurrency, which is the concurrent access of the same data by multiple users. Without sufficient concurrency controls, data could be updated or changed improperly, trading off with data integrity. To manage data concurrency is to make each user wait for a turn.
The goal of a database management system is to decrease the waiting time so it is either nonexistent or negligible to each user. The data manipulation language statements should proceed with as little intervention as possible, and destructive interactions among concurrent transactions should be prevented.
Destructive interaction is any interaction that updates data or alters underlying data structures incorrectly. Neither performance nor data integrity can be sacrificed. Oracle solves such problems by using various types of locks and a multi-version consistency model.