It’s Time to Move on from Two Phase Commit

2PC occurs after transaction is processed, and thus necessarily increases the latency of the transaction by an amount equal to the time it takes to run the protocol. To summarize the problems we discussed above: 2PC poisons a system along four dimensions: latency (the time of the protocol plus the stall time of conflicting transactions), throughput (because it prevents conflicting transactions from running during the protocol), scalability (the larger the system, the more likely transactions become multi-partition and have to pay the throughput and latency costs of 2PC), and availability (the blocking problem we discussed above). Therefore, they have to wait until the end of transaction processing (when all important state is made durable) and proceed in the necessary two phases: in the first phase, each worker publically relinquishes its control to abort a transaction, and only then can the second phase occur in which a final decision is made and disseminated.

Source: dbmsmusings.blogspot.com