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Abstract

Serializability across distributed transactions is guaranteed by selectively committing and aborting or delaying transactions to enforce an order of commitment that is the same as an order of performance of conflicting component operations of the transactions. A first memory access operation in a first transaction, for example, conflicts with a second memory access operation in a second transaction when the two memory access operations reference the same memory location and at least one of the operations is a write operation. The transaction processing system may permit a second transaction to read data written by a write operation of a first transaction before the first transaction is committed. In this case, depending on the respective order in which the two conflicting operations occur, the order of commitment is enforced, possibly by aborting either of the two transactions, to ensure that the order of commitment is the same as the order of the operations. The conflicts, for example, are detected when the addresses are determined during preparation of the transactions. The component operations may be scheduled for most efficient use of the computer system capabilities. In a multiprocessor system in which a global coordinator communicates with a plurality of transaction processors by way of 'prepare' and 'commit' commands, the commitment order is referenced to delay acknowledging that a transaction has been 'prepared' until the transaction's 'abort set' has been minimized.

First Claim