what are the concurrency contol?

Concurrency control is a database management systems (DBMS) concept that is used to know about conflicts while accessing or altering of data that can occur with multi-user system.concurrency control is used to coordinate simultaneous transactions while preserving data integrity.it is used to control the multi-user access of database.But,the concurrent execution of transaction may lead to data consistency and integrity problems.The following are the different problems associated with the concurrency control,
1.lost updates
2.uncommitted data
3.inconsistant data retrieval.
There are four types of anomalies:
1.atomicity 2.consistency 3.isolation 4.durability