Um Protocolo de Atomicidade Local Híbrida para Tratar Transações de Políticas Otimista, One e Two-Phase Locking, com Possibilidade de Extensão

Resumo

In this work, we allowed the transactions with threedistinct policies – optimistic (O), one-phase locking(1PL) and two-phase locking (2PL) – sharingsimultaneously each participant application object. Ourcontributions are extensions from the [7, 6, 1, 16]approaches, with focus on the pessimistic policy. Weplaced the lock request in the invocation event handlerto enable asynchronous mode for interaction messages.This solution restricts the concurrency chances whereasreturn conditions cannot be used in the conflict table[7]. We have added two measures for compensate thisrestriction. The 2PL transactions dispose of oneexclusive version for each participant object, during thefirst phase, and the validation action was deferred tothe end of this phase. These measures have avoided theunnecessary locking time until the execution phasebeginning. The 1PL transactions conflict table have gottwo changes: the conflict condition meaning [16] wassubstituted from update to execution error; and a newthird condition U was created and its meaning is a firstlevel operation code with some reference/assignprimitives which need be serialized. These measureshave enabled the second level derived operations(read/write primitives) keep locked only during theirfirst level operation run time, and when this first leveloperation response event returns, these read/writeprimitives are unlocked.