System R: An architectural overview

System R is an experimental data base management system that was designed t o be unusually easy to use. System R supports a high-level relational user language called SQL, which may be used by ad hoc users at terminals or by p rogrammers as an imbedded data sublanguage in PL/I or COBOL. This paper des cribes the overall architecture of the system, including the Relational Dat a System (RDS) and the Research Storage System (RSS). RDS is a data base language compiler. Host language programs with imbedded SQL, statements are compiled by System R, which replaces the SQL. statement s with calls to a machine-language access module. The compilation approach removes much of the work of parsing, name binding, and optimization from th e path of a running program, enabling highly efficient support for repetiti ve transactions. In contrast, the RSS is a low-level DBMS, supporting simpl e record-at-a-time operators, but with rather sophisticated transaction man agement, recovery, and concurrency control.