Title: RC-OCP: Reverse Coordinated Optimized Commit Protocol


Ganpat Singh Chauhan

Department of Computer Science, Swami Keshvanand Institute of Technology, Management & Gramothan, Jaipur (INDIA),

Mukesh Kumar Gupta

Department of Computer Science, Swami Keshvanand Institute of Technology, Management & Gramothan, Jaipur (INDIA)


With the growth of trends in computing and requirement for developing a reliable computing environment the need for performing tasks in distributed manner has gained much importance. Atomic commit protocols are used to preserve the ACID property in distributed systems when several sites need to
update their database with the same information. A variety of protocols have been proposed for last few decades, but among all Two-Phase Commit (2PC) are most widely used. 2PC is a blocking protocol, i.e. If a coordinator fails while the participants are waiting for a decision in its uncertain state, all the participants remain in a blocked state till the coordinator recovers and terminates the transaction. This is undesirable as these sites may be holding locks on the resources. In the event of message loss, the 2PC protocol will result in the sending of more messages. As an alternative, non-blocking atomic commit protocol has been suggested: This non-blocking protocol is Three-Phase Commit (3PC) protocol, which requires an extra phase (pre-commit) to
remove blocking state.

Although, the existing protocols are sufficient to ensure that ACID properties are maintained in a distributed transaction environment, but the substantial cost associated with the normal transaction execution adversely affects the performance of the system. These protocols require so many messages  transfer from the coordinator to participants and vice versa during different phases and corresponding increase communication and time complexity and hold the locks acquire by different participants till the end of last phase, forcing other transactions also to be blocked just because of the objects that are locked. All the existing protocols give the same performance for both deferred and immediate consistency constraints databases. Lots of protocols are
being proposed and mainly the concentration was to make the 2PC protocol non-blocking or to minimize the blocking possibilities in 2PC. There has been a renewed interest in developing and optimization of more efficient ACPs. This is also crucial in modern electronics and e-commerce environment which are characterized by high volume of transactions at several levels.

This paper is an effort to propose a new technique to optimize atomic commit protocols by optimizing voting phase based on deferred and immediate consistency constraints. Also an attempt has been made to propose reduction in communication complexity which will require less number of messages to be shared between coordinator and participants, the cost of execution as well as time delays.