Transactions

In the context of a distributed system, transactions have to be "ACID". ACID properties are defined as follows:

• Atomicity - A transaction either commits or rollsback. If it commits, all the changes take effect. If a transaction rolls back, all changes are undone.
• Consistency - A transaction always leads to the correct transformation of the system without endangering the integrity of the system
  
• Isolation - Concurrent transactions are isolated from the changes made by other incomplete transactions
• Durability - If a transaction commits, all the changes will be persisted and not undone. This means it will survive system failure.