OCP: a distributed real time commit protocol

Most of the existing commit protocols try to improve the system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. However, these protocols block the borrower when it tries to send WORKDONE/PREPARED message (Qin & Liu 2003, Haritsa, Ramamritham & Gupta 2000, Gupta, Haritsa, Ramamritham & Seshadri 1996, Gupta, Haritsa, & Ramamritham 1997), thus increasing the transactions commit time. This paper first analyzes all kind of dependencies that may arise due to data access conflicts in executing-committing transaction when a committing cohort is allowed to lend its data to an executing cohort, and then proposes a static two phase locking based optimistic commit protocol i.e. OCP. In OCP, the execution phase of a cohort is divided into two parts locking phase and processing phase and then, in place of WORKDONE message, WORKSTARTED message is sent just before the start of processing phase of the cohort. Again, in case of dependency, borrower with only commit dependency is allowed to send WORKSTARTED message instead of being blocked. This reduces the time needed for commit processing and is free from cascaded aborts. To ensure non-violation of ACID properties, checking of completion of processing and removal of dependency of cohort are required before sending the Yes-Vote message. The performance of the OCP is also analyzed for partial read-only optimization. .