Two-phase commit is a classical way to record highly reliable transaction into a classical database system. It makes however sense to implement in a Blockchain context as well as a basic blockchain protocol. In such a protocol on the one hand transactions and somehow the committing phase as well are supported by cryptography like all information processing phase are signed by a private key of the node that initiates, resulting that the whole voting process can be much less hacked. On the other hand transaction manager is usually a centralized role that can be easily imagined by a decentralized P2P network working with a consensus protocol providing Byzantine fault tolerance. If the transaction is committed both by the voters and the blockchain network it can be saved into the transaction database. Certainly it is a question if both voters and validators are required or we might as well mix somehow the two roles. Another interesting question might be how much more security does such a system provide comparing to other solutions.
