The
cautious scheduler, recently proposed for the concurrency control of database systems, never resorts to abortions or rollbacks for the purpose of concurrency control. The comprehensive performance evaluation study among different cautious schedulers and conventional non-cautious schedulers, however, has not yet been attempted. In this paper, we consider five scheduling algorithms and investigate their performance by means of simulation studies. Two of these algorithms are non-cautious; that is, the
two-phase locking algorithm (2PL) (the most popular transaction scheduling algorithm in practical systems) and the
conflict serializable algorithm (CSR) (a typical scheduling algorithm among those not using a locking mechanism; also called
D-serializable algorithm, conflict preserving serializable algorithm, or
WW-serializable algorithm). The others are cautious scheduling algorithms modified from the above
2PL and
CSR; that is,
cautious two-phase locking algorithm (C2PL), exclusive preclaimed two-phase locking algorithm (EP2PL), and
cautious conflict serializable algoritm (CCSR). The results demonstrate the superiority of the cautious conflict serializable algorithm over the conventional two-phase locking algorithm, especially in the on-line system environment.
Key Words Concurrency control - database - scheduler - performance evaluation
This work was supported in part by the Ministry of Education, Science and Culture of Japan under Scientific Research Grant-in-Aid and in part by the Advancd Systems Foundations of British Columbia, Canada.