1
                                                                    EXHIBIT 99.6

                                  March 7, 1999

BMC Software, Inc.
2101 CityWest Blvd.
Houston, Texas  77042


         Re:      Distribution Agreement (the "Distribution Agreement") by and
                  among New Dimension Software Ltd. (the "Company"), Boole &
                  Babbage Europe (the "Distributor") and Boole & Babbage, Inc.
                  ("BBI") dated October 28, 1994, as amended through the date
                  hereof.

Gentlemen:

         In consideration for you entering into that certain Share Purchase and
Tender Agreement dated on even date herewith, the Company hereby agrees not to
give a Termination Notice to the Distributor in connection with its Business
Transaction with you before April 10, 1999.

         In addition, each of the Company and you, on behalf of BBI and the
Distributor, agree that as soon as practicable after the consummation of the
Business Transaction between you and BBI we shall enter into the Fourth
Amendment to the Distribution Agreement, which shall be in substantially the
form attached hereto as Exhibit A.

         All terms not otherwise defined herein shall have the same meaning
afforded in the Distribution Agreement.


                                     New Dimension Software, Inc.


                                     By: /s/ RONI A. EINAV
                                        ---------------------------------------
                                     Name:   Roni A. Einav
                                          -------------------------------------
                                     Title:  Chairman
                                           ------------------------------------


                                     By: /s/ DAN BARNEA
                                        ---------------------------------------
                                     Name:   Dan Barnea
                                          -------------------------------------
                                     Title:  CEO
                                           ------------------------------------


Agreed and Accepted this 
7th day of March, 1999:

BMC Software, Inc.


By: /s/  M. BRINKLEY MORSE
   ----------------------------------
Name:    M. Brinkley Morse
Title:   Senior Vice President


   2
                                                                       EXHIBIT A

                                FOURTH AMENDMENT
                                       TO
                             DISTRIBUTION AGREEMENT
                      DATED OCTOBER 28, 1994 AS AMENDED ON
                APRIL 24, 1997, OCTOBER 31, 1997 AND MARCH , 1999


This Amendment is made and entered into as of this ____ day of __________, 1999.

                                      Among

                  NEW DIMENSION SOFTWARE LTD.
                  a corporation organized and existing under the laws of Israel
                  with its principal place of business at Bldg. 7, Alaim
                  Industrial Park, P. O. Box 43227, Tel Aviv, Israel 61430
                  (hereinafter referred to as: the "Company")

                                       and

                  BOOLE & BABBAGE EUROPE
                  a corporation organized and existing under the laws of the
                  Republic of Ireland with its principal place of business at
                  Sadyford Business Centre, Burtonhall Road, Faxrock Dublin 19,
                  Ireland (hereinafter referred to as: the "Distributor")


WHEREAS           on October 26, 1994, the Company and the Distributor entered
                  into a distribution agreement (hereinafter: "the 1994
                  Distribution Agreement") whereby the Distributor was granted
                  exclusive distribution rights in certain territories with
                  respect to certain proprietary Software Products of the
                  Company; and

WHEREAS           the 1994 Distribution Agreement has been amended by the
                  Company and Distributor on April 24, 1997 (hereinafter: the
                  "First Amendment"), on October 31, 1997 (hereinafter: the
                  "Second Amendment") and on March ___, 1999 (hereinafter: the
                  "Third Amendment") and the Company, Distributor and Boole &
                  Babbage, Inc., the parent company of Distributor ("Boole"),
                  have entered into that certain letter agreement dated December
                  22, 1998, which provides for additional agreements between the
                  Company and Distributor with respect to the Company's right to
                  notify Distributor of its termination of the Distribution
                  Agreement in connection with the announcement by BMC Software,
                  Inc. ("BMC") of its acquisition of Boole (the "Letter
                  Agreement"); and


                                       -1-

   3



WHEREAS           the Company and Distributor wish to amend certain provisions
                  of the 1994 Distribution Agreement, the First Amendment, the
                  Second Amendment, the Third Amendment and the Letter
                  Agreement, subject to and in accordance with the provisions
                  and conditions herein.


NOW, THEREFORE, in consideration of the mutual promises and covenants contained
herein, the parties hereby agree as follows:

1.       Preamble, Schedules and Captions

         The Preamble to this Fourth Amendment constitutes an integral part
         hereof. This Fourth Amendment's captions are provided for the sake of
         convenience and shall not be used to construe the provisions hereof.

2.       Definition, Terms and Provisions of the 1994 Distribution Agreement,
         First Amendment, Second Amendment, Third Amendment and the Letter
         Agreement

         Except as expressly provided for herein, all the definitions, terms and
         provisions of the 1994 Distribution Agreement, the First Amendment, the
         Second Amendment, Third Amendment and the Letter Agreement shall apply
         hereto mutatis mutandis.

3.       Sections 7.2 and 7.3 of the 1994 Distribution Agreement are hereby
         amended to read in their entirety as follows:

         "7.2     The Terminating Party may terminate the Agreement, should it
                  elect to do so at its sole and exclusive discretion, during a
                  period of 10 (ten) months as of the last day of the quarter in
                  which the Triggering Event has occurred (or, in the event of a
                  Business Transaction by the Distributor with BMCS, occurring
                  at any time between the effective date of the Second Amendment
                  (October 31, 1997) and up to December 31, 1999) by giving the
                  other party a written notice of its intention to so terminate
                  the Agreement (hereinafter: the "Termination Notice");
                  provided, that the Company shall not give a Termination Notice
                  to the Distributor in connection with its Business Transaction
                  with BMC Software before the day first succeeding the
                  termination of BMC Software's tender offer to acquire ordinary
                  shares NIS 0.01 of the Company.

           7.3    If a Termination Notice has been given by the Terminating
                  Party to the other party hereof, the Agreement shall be
                  terminated within 60 days as of the receipt of such
                  Termination Notice (hereinafter the "Effective Termination
                  Date")."

4.       Effective Date

         The effective date of this Fourth Amendment is ______________, 1999.

5.       General


                                       -2-

   4


         5.1      Other than as expressly stated and amended hereinabove the
                  1994 Distribution Agreement as amended in the First Amendment,
                  the Second Amendment and the Third Amendment and the Letter
                  Agreement, and the terms and provisions therein, shall
                  continue to exist and bind the parties and nothing contained
                  herein shall be deemed to derogate from or change the 1994
                  Distribution Agreement, and the First Amendment, the Second
                  Amendment and the Third Amendment and the Letter Agreement
                  thereof or any of the parties' rights and obligations in
                  accordance therewith other than as expressly provided for
                  herein and in the Letter Agreement. However, should any
                  provision herein contradict any provision of the 1994
                  Distribution Agreement, the First Amendment, the Second
                  Amendment, the Third Amendment or the Letter Agreement, this
                  Fourth Amendment shall prevail.

         5.2      The provisions contained herein set forth the entire amendment
                  of the 1994 Distribution Agreement as amended in the First
                  Amendment, the Second Amendment and the Third Amendment with
                  respect to the subject matter hereof and supersedes all
                  previous communications, representations or agreements
                  (excluding the Letter Agreement), whether oral or written with
                  respect to the subject matter hereof.

         5.3      Subject to any legal duty to which both parties, being public
                  companies, are subject, the contents and timing of any public
                  announcement or press release regarding this Third Amendment
                  are to be approved in advance by the designated officers of
                  the parties hereto. In case of the Company the designated
                  officer is the Company's Chief Executive Officer and in case
                  of the Distributor the designated officer is the Chief
                  Financial Officer of Boole & Babbage Inc.


IN WITNESS WHEREOF, the parties have executed this Fourth Amendment.



New Dimension Software Ltd.                  Boole & Babbage Europe



By:                                          By:
   ------------------------------               ------------------------------
Name:                                        Name:
     ----------------------------                 ----------------------------
Title:                                       Title:
      ---------------------------                  ---------------------------


                                       -3-