Saturday, 9 August 2014

Two Phase Commit protocol control messages

The list of control messages used by 2PC to control a distributed transaction / What are the control messages used by 2PC to handle transaction and recovery?


The following are the control messages used by 2 Phase Commit (2PC) protocol for handling concurrent transactions;

<Prepare T> - Sent by the Transaction Coordinator of Transaction T to all the Participating Sites where Transaction T is executed.

<Ready T> - Sent by the Transaction Managers of all the participating sites whichever is ready to commit the Transaction T.

<No T> - Used by any Transaction Manager of the participating sites which is not ready for committing the Transaction T. This message is stored in the local log file of the participating site which is not ready for commit.

<Abort T> - Sent by a Transaction Manager of participating site which is not ready for commit. Also, sent by Transaction Coordinator to all participating sites to abort the Transaction T.

<Commit T> - Sent by Transaction Coordinator of Transaction T, if TC received <ready T> messages from all the participating sites.

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