Three-Phase Commit (3PC)
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Three-Phase Commit (3PC) is a distributed transaction protocol used to coordinate transactions across multiple nodes or databases in a distributed system. It extends the traditional two-phase commit (2PC) protocol by adding an extra phase to improve fault tolerance and reduce the likelihood of blocking. In 3PC, the transaction coordination process is divided into three phases: preparation, pre-commit, and commit. During the preparation phase, each participant node in the distributed transaction prepares to commit by ensuring that it can commit the transaction successfully. In the pre-commit phase, each participant sends a “ready to commit” message to the coordinator, indicating its preparedness. If all participants are ready, the coordinator sends a pre-commit message to all participants in the commit phase, instructing them to commit the transaction. Unlike 2PC, 3PC introduces a timeout mechanism in the pre-commit phase, allowing participants to proceed with committing the transaction even if the coordinator fails. However, 3PC still suffers from the blocking problem in certain failure scenarios, leading to potential performance issues. Despite this limitation, 3PC offers improved fault tolerance compared to 2PC, making it a valuable protocol for ensuring data consistency and integrity in distributed systems. s://en.wikipedia.org/wiki/Three-phase_commit_protocol