What are the challenges of pessimistic concurrency in databases?

What are the challenges of pessimistic concurrency in databases?

Pessimistic concurrency control assumes conflicts will occur, locking resources to prevent them. This can lead to issues like deadlocks, reduced performance due to waiting, and increased complexity in managing locks.

Can you explain deadlocks in more detail?

Sure! A deadlock occurs when two or more transactions are waiting for each other to release locks, creating a cycle of dependencies that prevents any of them from proceeding.

How can we prevent deadlocks?

Deadlocks can be prevented by using techniques like lock timeouts, resource ordering, or deadlock detection algorithms that periodically check for cycles in the wait-for graph.

Are there alternatives to pessimistic concurrency?

Yes, optimistic concurrency control is an alternative. It allows transactions to proceed without locking resources, checking for conflicts only at commit time.

What are the pros and cons of optimistic concurrency?

Optimistic concurrency can improve performance in low-conflict scenarios but may lead to higher rollback rates in high-conflict situations.