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Quiz questions on deadlocks, lock based protocols, granularity, types of reads like insertion, deletion and predicate and the concept of concurrency in index structures.
Concurrency control (CC) is a fundamental component of a database management system (DBMS) that ensures that multiple transactions can run simultaneously without interfering with each other or compromising the database's integrity. CC ensures that data is updated correctly when multiple transactions are executed concurrently.
CC mechanisms include: Pessimistic concurrency control: Delays transactions if they conflict with other transactions, ensuring that all transactions can be executed correctly, but transactions are slow and throughput is reduced Optimistic concurrency control: If there is no conflict, make all changes take effect If there is a conflict, resolve it, typically by aborting the transaction
Other CC techniques include: Two-phase locking protocol, Time stamp ordering protocol, Multi version concurrency control, and Validation concurrency control. CC is especially important in the following areas: Database management systems (DBMS), Transactional systems, Operating systems, and Distributed applications.
To avoid concurrency control problems, some rules are made to maintain consistency and serializability during the execution of concurrent transactions. For example, locking is the process by which a DBMS restricts access to a row in a multi-user environment. When a row or column is exclusively locked, other users are not permitted to access the locked data until the lock is released.
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