Adaptable correctness through two-dimensional locking

It is widely recognized that advanced database applications stress the limits of the functionality and performance of traditional transaction management, and that advanced transaction management is needed for these applications. We present a new adaptable correctness criterion (ACC) which describes the legal interleaving of transactions in an environment where transactions may have different correctness requirements. ACC determines an actual correctness criterion (actualCC) that dynamically changes over time. The actualCC describes the legal interleaving of the currently executing transactions, and is determined based on correctness requirements associated with the current transactions. To support ACC, we introduce a new locking method called two dimensional locking. In two dimensional locking, each lock consists of two separate component locks, which represents two different dimensions when transaction characteristics are concerned. One dimension describes the interleaving constraint for the transaction, while the other dimension describes the effect the transaction has on the database.