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

Integrated Database Management System

    (IDMS) A network DBMS written by the staff of
   B.F.Goorich (Akron, Ohio, USA) circa 1972 and sold to
   Cullinet (Originally Cullinane, now part of Computer
   Associates).

   IDMS was licensed to ICL in 1976 for porting to, and
   subsequent development on, their computers.  It was
   implemented on the ICL 1900 Series (DME George 2,
   George 3, CME, TME), System 4, and ICL 2900 Series
   (later Series 39 Corporate Servers).  The latest version runs
   on Series 39 OpenVME as IDMSX (IDMS extended).

   [Was it a relational database?]

   (1995-04-19)