What are the different types of locks used in databases?

What are the different types of locks used in databases?

In databases, 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 locks work?

Sure! Shared locks allow multiple transactions to read a resource simultaneously. However, while a shared lock is in place, no transaction can acquire an exclusive lock on that resource until all shared locks are released.

What happens if two transactions try to acquire an exclusive lock at the same time?

If two transactions attempt to acquire an exclusive lock on the same resource simultaneously, one will succeed while the other will be blocked until the first transaction releases the lock.

Are there any drawbacks to using locks in databases?

Yes, using locks can lead to issues like deadlocks, where two transactions are waiting on each other to release locks, and can also reduce concurrency, impacting performance.