What are the types of locks in database systems?

What are the different types of locks used in database systems?

In database systems, the main types of locks are shared locks, exclusive locks, and update locks. Shared locks allow multiple transactions to read a resource, while exclusive locks prevent other transactions from accessing the resource. Update locks are used to prevent deadlocks when a transaction intends to update a resource.

Can you explain how shared and exclusive locks work?

Sure! A shared lock allows multiple transactions to read a resource simultaneously, but no transaction can modify it. An exclusive lock, on the other hand, allows a transaction to both read and modify a resource, blocking all other transactions from accessing it until the lock is released.

What happens if a transaction tries to access a locked resource?

If a transaction tries to access a locked resource, it will be blocked until the lock is released. This ensures data integrity and prevents conflicts between transactions.

Are there any drawbacks to using locks in databases?

Yes, while locks are essential for data integrity, they can lead to performance issues like deadlocks and reduced concurrency if not managed properly.