Extended commitment ordering, or guaranteeing global serializability by applying commitment order selectively to global transactions

Abstract

The Extended Commitment Ordering (ECO) property of transaction histories (schedules) generalizes the Commitment Ordering (CO) property defined in [Raz 90]. In a multi resource manager (RM) environment ECO guarantees global serializability when supported locally by each RM that participates in global transactions (i.e., transactions that span more than a single RM) and provides local serializability (by any mechanism). ECO assumes that a RM has the knowledge to distinguish local transactions (i.e., transactions confined to that RM) from global transactions. ECO imposes an order condition, similar to the CO condition, on the commit events of global transactions only, and thus, it is less constraining than CO.Like CO, ECO provides a fully distributed solution to the long standing problem of guaranteeing global serializability across RMs with different concurrency control mechanisms. Also, like CO, no communication beyond atomic commitment (AC) protocol messages is required to enforce ECO.When RMs are provided with the information about transactions being local, and are coordinated solely via AC protocols (have the extended knowledge autonomy property), ECO, applied locally together with local serializability in each RM involved with global transactions, is a necessary condition for guaranteeing global serializability.ECO reduces to CO when all the transactions are assumed to be global (e.g. if no knowledge about the transactions being local is available).