Define Two phase commit
Two phase commit: To make sure atomicity, all the sites where a transaction is being executed must agree on the final outcome of the execution. The transaction should either commit at all sites or it must abort at all sites. For this very simple protocol is two-phase commit that has the voting phase and the decision phase, within the voting phase the sub-transactions are requested to vote on their willingness to commit/abort. In the decision phase the decision as to if all sub-transactions must commit or abort is made and performed. The transactions at a site interact along with the transaction manager of the site, cooperating in the exchange of messages by which the two -phase commit is executed.