After the design of the Gamma software was completed in the fall of 1984, work began on the first prototype which was operational by the fall of 1985. This version of Gamma was implemented on top of an existing multi- computer consisting of 20 VAX 11/750 processors [DEWI84b]. In the period of 1986-1988, the prototype was enhanced through the addition of a number of new operators (. aggregate and update operators), new parallel join methods (Hybrid, Grace, and Sort-Merge [SCHN89a]), and a complete concurrency control mechanism. In addi- tion, we also conducted a number of performance studies of the system during this period [DEWI86, DEWI88, GHAN89,.
