Two-Phase Commit (2PC)

The Two-Phase Commit (2PC) protocol is an atomic commitment protocol used in distributed systems, databases, and computer networking to coordinate a distributed atomic transaction. It ensures that all participating processes (participants) either commit or abort the transaction consistently, maintaining data integrity across multiple nodes. The protocol is designed to handle temporary system failures, using logging mechanisms to recover from crashes and maintain state. In a normal execution, 2PC operates in two phases: a commit-request phase where the coordinator asks participants to prepare for commit, and a commit phase where the coordinator instructs participants to either commit or rollback based on their votes. This protocol is widely used to guarantee atomicity in distributed transactions, ensuring that either all changes are applied or none are, thus preventing data inconsistencies. However, it is susceptible to blocking issues if the coordinator fails permanently.