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

ADABAS

    A relational database system by Software AG.
   While it was initially designed for large IBM mainframe
   systems (e.g. S/370 in the late 1970s), it has been ported
   to numerous other platforms over the last few years such as
   several flavors of Unix including AIX.

   ADABAS stores its data in tables (and is thus "relational")
   but also uses some non-relational techniques, such as
   multiple values and periodic groups.

   (1995-10-30)