Final answer:
The theory of concurrency control in databases mainly revolves around the concept of transactions, employing techniques such as locking, timestamp ordering, and optimistic concurrency control to manage simultaneous execution while maintaining data integrity.
Step-by-step explanation:
Most of the theory concerning concurrency control in databases is developed in terms of transactions. In the field of databases, a transaction is a sequence of database operations that satisfies the ACID properties (Atomicity, Consistency, Isolation, Durability), which ensure that the database remains in a consistent state even in cases of system failures or concurrent transaction executions. Concurrency control is critical for database systems as it manages the simultaneous execution of transactions, preventing potential conflicts and ensuring integrity of data.
There are several concurrency control techniques, like locking, where transactions must acquire locks before accessing data, timestamp ordering, which assigns a unique timestamp to each transaction to dictate the order in which transactions should proceed, and optimistic concurrency control, which assumes that multiple transactions can complete without interfering with each other and only checks for conflicts at the end of a transaction. Each of these methods attempts to maximize the number of concurrent transactions while maintaining the consistency of the database.