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                                                                     EXHIBIT 4.3

                          FIRST SUPPLEMENTAL INDENTURE

      FIRST SUPPLEMENTAL INDENTURE, dated as of December     , 2003, by and
between EMC Corporation, a Massachusetts corporation ("EMC"), and Wilmington
Trust Company, as Trustee (the "Trustee"), under the Indenture dated as of April
5, 2002 (the "Indenture").

      WHEREAS, the Indenture was authorized, executed and delivered by
Documentum, Inc., a Delaware corporation ("Documentum"), to provide for the
issuance by Documentum of Documentum's 4.5% Senior Convertible Notes Due 2007
(the "Notes"); and

      WHEREAS, pursuant to the Agreement and Plan of Merger (the "Merger
Agreement") dated as of October 13, 2003 by and among EMC, Elite Merger
Corporation, a Delaware corporation and wholly owned subsidiary of EMC ("Merger
Sub"), and Documentum, Merger Sub has merged with and into Documentum, with
Documentum surviving as a wholly owned subsidiary of the Company (the "First
Merger"); and

      WHEREAS, immediately following the First Merger, EMC merged Documentum
with and into EMC, with EMC surviving the merger and the separate corporate
existence of Documentum ceasing (the "Subsidiary Merger"); and

      WHEREAS, EMC hereby requests that the Trustee execute this First
Supplemental Indenture.

      NOW, THEREFORE, THIS FIRST SUPPLEMENTAL INDENTURE WITNESSETH, that, in
consideration of the premises, it is mutually agreed, for the benefit of each
other and for the equal and proportionate benefit of all Holders of the
Securities, as follows:

                                   ARTICLE I

                             AMENDMENT OF INDENTURE;
                           ASSUMPTION OF OBLIGATIONS

      1.01 Definitions. Terms used in this First Supplemental Indenture and not
defined herein have the respective meanings ascribed to them in the Indenture.

      1.02 Revision of Conversion Price. The form of reverse of Security, set
forth in Section 2.03 of the Indenture, is hereby amended by deleting the
reference to the Conversion Price being $30.02 and revising such amount to be
$13.802298. For all purposes of the Securities and the Indenture, the Conversion
Price shall be as revised pursuant to this First Supplemental Indenture.
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      1.03 Convertibility of Securities. The Securities shall be convertible
into the kind and amount of shares of stock, securities or other property or
assets (including cash) receivable upon the First Merger by a holder of a number
of shares of Common Stock issuable upon conversion of such Securities
immediately prior to the First Merger.

      1.04 Express Assumption of Obligations. In accordance with Section 8.01 of
the Indenture, EMC hereby expressly assumes the due and punctual payment of the
principal of and interest on all the Securities and the performance or
observance of every covenant of the Indenture on the part of Documentum to be
performed or observed.

                                   ARTICLE II

                                  MISCELLANEOUS

      2.01 Severability. In case any provision in this First Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

      2.02 Governing Law. THIS FIRST SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

      2.03 Ratification. This First Supplemental Indenture is a supplement to
the Indenture. As supplemented by this First Supplemental Indenture, the
Indenture is in all respects ratified, approved and confirmed and the Indenture
and this First Supplemental Indenture shall together constitute one and the same
instrument.

      2.04 Counterpart Originals. The parties may sign any number of copies of
this First Supplemental Indenture. Each signed copy shall be an original, but
all of them together represent the same agreement.

      2.05 The Trustee. the Trustee shall not be responsible in any matter
whatsoever for or in respect of the validity or sufficiency of this First
Supplemental Indenture or for or in respect of the Recitals contained herein.


                            [Signature Page Follows]


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      IN WITNESS WHEREOF, this First Supplemental Indenture has been executed
and delivered by EMC Corporation and Wilmington Trust Company, as Trustee, as of
the day and year first above written.

                                           EMC CORPORATION


                                           By:___________________________
                                                Name:
                                                Title:


                                           WILMINGTON TRUST COMPANY,
                                                    As Trustee

                                           By:___________________________
                                                Name:
                                                Title:


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