V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DB2
       DataBase 2 (IBM, DB)


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

DB2

    A relational database from IBM.

   When running under IBM's MVS (Multiple Virtual Storage)
   operating system, DB2 is implemented on top of VSAM and
   uses its underlying data structures.

   DB2, later called "DB2 Universal DataBase", also runs under
   windows NT, AIX, Solaris and, most recently, Linux.

   [Details?  Was there a "DB1"?]

   (1999-02-01)