“…Recently, there has been much effort to improve the performance of database machines by achieving more parallelism in their architectures such as MICRONET [Su, 1978], EDC [Uemura, 1980], MDBS [Hsiao, 1983], DBC/1012~eradata, 1984, GAMMA [DeWkt, 1986], REPT [Shultq 1984], HYPERTREE [Despain, 1978;Sequine, 1978], DIRECT [Boral, 1982], GRACE [Kltsuregawa, 1985], DBMAC [Missikoff, 1981;Missikoff, lW, Missikoff, 19@ Cesaritti, 1983], and SM3 [Bar% 1986]. The major advantages of using a multicomputer architecture are 1) component reliability, 2) component availability, 3) cost-effectiveness, and 4) expandability.…”