What are transaction isolation levels?

What are transaction isolation levels supported by Oracle?

Oracle supports 3 transaction isolation levels:

1. Read committed (default)
2. Serializable transactions
3. Read only

What are transaction isolation levels supported by Oracle?

READ COMMITTED:
If row locks are obtained by a certain transaction, then any other transaction that contains DML needs to wait until the row locks have been released by that particular transaction.

SERIALIZABLE:
If a serializable transaction contains DML that updates a resource that has been updated in another transaction but which has not committed yet, then the DML statement fails.