Three-Phase Commit Mechanism Explanation

The three-phase commit protocol is an improved version of the two-phase commit protocol.

• Ask Phase: The transaction manager sends a commit request to each participant. If a resource manager can commit, it returns a "Yes" response; otherwise, it returns a "No" response.
• Prepare Phase: Based on the feedback from the resource managers, the transaction manager decides whether to proceed further. There are two possibilities:
  • If all participants return "Yes", the transaction is executed (committed).
  • If any participant sends a "No" response, or if no responses are received within the timeout period after waiting for them from all resource managers, then the execution of the transaction is aborted.
• Commit Phase: This phase performs the actual commit of the transaction.