The Free On-line Dictionary of Computing (30 December 2018):

System R

    A database system built as a research project at
   IBM San Jose Research (now IBM Almaden Research Center) in
   the 1970s.  System R introduced the SQL language and also
   demonstrated that a relational system database could provide
   good transaction processing performance.

   (http://mcjones.org/System_R/).

   (1998-09-29)