Reducing the blocking in two-phase commit with backup sites

The blocking phenomena in two-phase commit (2PC) reduces the availability of the system as the blocked transactions keep all the resources until the recovery of the coordinator. The three-phase commit (3PC) protocol involves an extra round of message transmission to resolve the blocking problem. In this paper, we propose a backup commit (BC) protocol to reduce the blocking problem by attaching multiple backup sites to the coordinator site. In BC, after receiving responses from the participants, the coordinator quickly communicates the final decision to the backup sites, before it sends the final decision to the participants. When blocking occurs, the participant sites can terminate the transaction by consulting a backup site of the coordinator. The BC protocol resolves the blocking in most of the coordinator site failures without involving an expensive communication cycle as in 3PC. The simulation experiments indicate that the throughput performance of BC is close to 2PC.