What are the two steps described in the two-phase commit protocol?

• A. First you check if the system is ready to commit; When it's ready to commit, you commit to the DB
• B. You always commit to the DB first, then check readiness
• C. Transactions are committed independently on each resource without coordination
• D. The protocol relies on a central coordinator to flood commit messages after preparing

Answer: (A)

Two-phase commit ensures a distributed transaction either commits everywhere or rolls back everywhere by coordinating across all participants. In the first phase, a central coordinator asks every resource if it can commit and each one responds after preparing to commit (a vote of yes or no). If all resources say yes, the second phase commits the transaction across all resources; if any resource cannot commit, the coordinator aborts across all of them. The option describing checking readiness first and then performing the commit matches this flow: you determine readiness (prepare) and only then issue the commit. The other choices either imply committing without coordination, or describe incorrect sequences, or oversimplify how the coordinator and messages work in 2PC.