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                                                                    EXHIBIT 2.2

                                    AMENDMENT

                                       TO

                 AGREEMENT AND PLAN OF MERGER AND REORGANIZATION

        This AMENDMENT TO AGREEMENT AND PLAN OF MERGER AND REORGANIZATION
("Amendment"), dated as of November 7, 1997, is entered into by and between
VMARK Software, Inc., a Delaware corporation ("VMARK") and Unidata, Inc., a
Colorado corporation ("UNIDATA").

        1.      The parties hereto have agreed upon and entered into that
certain Agreement and Plan of Merger and Reorganization dated as of October 7,
1997 (the "Merger Agreement"), which provides for and sets forth the terms of
the merger of UNIDATA with and into VMARK. All terms used herein that are not
otherwise defined herein shall have the meaning ascribed to them in the Merger
Agreement.

        2.      The parties now desire to amend certain provisions of the Merger
Agreement as follows:

                a.      Section 5.17 is hereby amended and restated in its
                entirety to read as follows:

                  "VMARK will enter into an agreement at the Effective Time to
                  provide registration rights to UNIDATA's stockholders with
                  respect to the shares of VMARK Common Stock received by them
                  in the Merger. Such agreement will provide each such holder of
                  VMARK Common Stock, for as long as such holder is unable to
                  sell, within any three month period, all of such holder's
                  shares of VMARK Common Stock received in the Merger under Rule
                  144 or Rule 145 under the Securities Act, unlimited
                  "piggyback" registration rights and two demand registrations
                  on Form S-3 (provided that a minimum number of shares are
                  registered in each demand registration), in each case on
                  customary terms and subject to reasonable blackout periods and
                  other restrictions."

                b.      Section 2.23 is hereby amended to delete the words "a
                majority" where such words occur on the first and second line
                thereof and insert in their place "two-thirds."

                c.      Section 3.02 is hereby amended to delete the number
                "8,522,568" where such number occurs on the second line thereof
                and insert in its place "8,272,486."



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                d.      Section 3 of the Escrow Agreement attached as Exhibit C
                to the Merger Agreement is hereby amended and restated in its
                entirety to read as follows:

                  "3.   INVESTMENT AND VOTING PENDING DISTRIBUTION. The Escrowed
                  Shares shall be held by the Escrow Agent subject to the
                  written directions of the Representatives to sell all or any
                  portion thereof, provided that no sale thereof shall be made
                  in violation of applicable securities laws. In the event of
                  any sale thereof, the resulting funds shall be invested in
                  short-term government securities or a mutual fund invested
                  substantially solely in such securities, as directed by the
                  Representatives. Any interest or dividends shall not be added
                  to or become part of the escrow account and shall be promptly
                  distributed from time to time to the Stockholders (as defined
                  in Section 5). The Escrowed Shares, until distributed out of
                  this escrow, shall be voted by the Escrow Agent in accordance
                  with the written directions of the Representatives."

        3.      This Amendment may be executed in two or more counterparts, all
of which shall be considered the same instrument and shall become effective when
executed and delivered by each of the parties.

        4.      Other than as expressly amended in Section 2 above, the Merger
Agreement remains unmodified and in full force and effect.


        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
signed by their respective officers, all as of the date first written above.




                                   VMARK SOFTWARE, INC.


                                   By: /s/ PETER GYENES
                                       ---------------------------------------- 
                                       Peter Gyenes
                                       President and Chief Executive Officer


                                   UNIDATA, INC.


                                   By: /s/ DAVID W. BRUNEL
                                       ---------------------------------------- 
                                       David W. Brunel
                                       President and Chief Operating Officer