Two-Phase Commit Protocol

What is Two-Phase Commit Protocol

The Two-Phase Commit (2PC) Protocol is a type of atomic commitment protocol (ACP) used in the distributed database system. It's a basic type of consensus protocol ensuring data consistency across all nodes in the network. Its primary use is maintaining synchronicity and stability during transactions in multi-node database systems.

Functionality and Features

The 2PC protocol functions in two phases:

  • Prepare Phase: A coordinator node receives a transaction request, then sends a prepare message to all participant nodes.
  • Commit Phase: Depending on the responses from participant nodes, the coordinator sends a commit or abort message. All nodes then commit or abort the transaction accordingly.


The architecture of the 2PC protocol consists of multiple nodes including coordinator and participant nodes. These nodes communicate in a distributed network to execute transactions.

Benefits and Use Cases

2PC protocol offers numerous benefits:

  • Ensures data consistency and stability in distributed database systems.
  • Handles complex, cross-network transactions efficiently.
  • Prevents data loss during network failures.

Challenges and Limitations

While 2PC has advantages, it also has limitations:

  • Susceptibility to blocking if the coordinator fails during the transaction.
  • Requires high communication overhead.
  • Lack of timeliness guarantees in a practical, asynchronous system.

Comparison with Similar Technologies

3PC (Three-Phase Commit Protocol) is an upgrade to 2PC, designed to overcome blocking issues. However, both protocols have their unique advantages and trade-offs.

Integration with Data Lakehouse

In a data lakehouse environment, the 2PC protocol can play a vital role in synchronising transactions. However, many modern data lakehouses use other data consistency models or transaction protocols to avoid the blocking issue inherent in 2PC.

Security Aspects

2PC protocol is not primarily designed with security features. Rather, it focuses on consistency and coordination. Security is usually managed at the database level.


Despite ensuring data consistency, 2PC can impact system performance negatively due to its blocking nature and communication overhead.

Comparisons with Dremio’s Technology

Dremio surpasses the 2PC protocol by providing a more scalable, high-performance, and non-blocking solution. Dremio's designs focus not just on data consistency, but also on maximising system performance and efficiency.


What is the Two-Phase Commit Protocol? It's a type of atomic commitment protocol used to ensure data consistency in distributed database systems.

What are the phases in 2PC? It consists of two phases: the Prepare Phase and the Commit Phase.

What are the limitations of 2PC? It's susceptible to blocking, requires high communication overhead, and lacks time guarantees.


Atomic Commitment Protocol (ACP): A type of protocol used to ensure consistency in distributed systems.

Consensus protocol: A protocol used to achieve agreement on a single data value among distributed processes.

Data Lakehouse: A new type of data platform that combines the best elements of data warehouses and data lakes.

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