. 4BSTRACT A number of recent studies hale exammed the performance of concurrent\control algorithms for database management s\stems The results reported to date rather than bemg defimove ha\e tended to be contradIctor> In 011s paper rather than presenting “yet another algorithm performance stud)” we crlbcally mvesngate the assumwons made m the models used m past studies and their Imphcatlons We employ a “complete” model of a database emlronment to study the relatn~ e performance of three dlfferent approaches to the concurrency control problem under a\arleb of modehng assumptions We shon how differences m the underlymg assumpnons explam the seemmgl\contradlctorq performance results We also examine how reahsnc the various assumptions would be for “real” database sqqtems

1 IWRODUCTION Research m the area of concurrency control for database systems has led to the development of many concurrenck control algorithms Most of these algorithms are based on one of three basrc mechamsms lodmg [Mena Rose78 Graj79 Lmd79 Ston79] rrmestamps [Reed78 Thorn79 BernSOb] and oprnrsru concurrency control (also called commit-hme\ahdabon or certdicanon) IBada79 Casa79 Kung81 Cer182] Bernstem and Goodman [Bern81 Bern821 sur\ey manv of the algorithms that hate been developed and describe how nea algorithms ma) be created b\combmmg the three basic mechanisms