关键词: Sagas模型, THP技术, 功能替代

Abstract: In order to improve the successful rate of transaction executing，and reduce the loss of system caused by executing compensate transaction in the traditional sagas model，this paper presents an improved model of Sagas——PRSagas based on apply beforehand and functional alternation.This model applies recourses beforehand which required by each sub-task of long transaction executing，then pre-analyzes each sub-task respectively and obtains the replacement set.After analyzing the feasibility of executing each substitution，this model selects the most succesful sub-transaction to compose the final execution of sub-task-flow.Through analysis and experiment，it shows the correctness and effectiveness of this model.

Key words: model of Sagas, Tentative Hold Protocol（THP）, functional alternation