Transactions
Transactions are tricky and it's hard to get it right. From the beginning it is quite straight forward and the simple solution is to only allow one transaction at a time. In the quest for better performance we will allow transaction to run concurrently and this is of course asking for trouble. Several techniques are presented such as locking, optimistic control and timestamps, to allow concurrency while preserving the requirements on Atomicity, Consistency, Isolation and Durability.