With the linear commit protocol, sites are connected in a chain, and the subtransaction at the left-hand end of the chain initiates the protocol. Propose a crash recovery protocol for a site in the chain. Consider the following three points at which the crash might occur and state in each case (1) how the site determines from its log that it is at that point and (2) what action it takes (beyond standard recovery processing)
(a) The site crashes before the first message from its left-hand neighbor arrives.
(b) The site crashes after sending the first message to its neighbor on the right, but before receiving a message from its neighbor on the right.
(c) The site crashes after sending a message to its neighbor on the left but before receiving the second message from its neighbor on the left.