Which type of lock prevents any other concurrent access?

An exclusive lock is designed to prevent any other concurrent access to a resource, which makes it the correct answer in this context. When an exclusive lock is applied to a database resource, it ensures that no other transactions can read from or write to that resource until the lock is released. This locking mechanism is crucial in situations where data integrity must be maintained during complex transactions, as it prevents conflicts that could arise from simultaneous operations.

Other types of locks, such as read locks, allow other transactions to read the locked resource but not write to it, thereby permitting some level of concurrent access. Write locks, on the other hand, allow one transaction to write while preventing others from also gaining write access, but they do not restrict read access in the same way as exclusive locks do. Access locks are generally less common and have a more specific purpose, focusing on permissions rather than preventing concurrent access entirely.

The nature of an exclusive lock is key in database systems, particularly in environments that require strict control over data transactions to avoid anomalies and ensure consistency. This makes it an essential concept to grasp for those working with databases.