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                                                                     EXHIBIT 2.1


                                 AMENDMENT NO. 2
                                       TO
                          AGREEMENT AND PLAN OF MERGER

         This Amendment No. 2 (the "Amendment") to Agreement and Plan of Merger
by and among META Group, Inc. ("META"), MG Acquisition Corporation ("Acquisition
Sub") and The Sentry Group, Inc. ("SENTRY") dated as of September 23, 1998 (the
"Agreement"):

                                   WITNESSETH:

         WHEREAS, each of the parties hereto is a party to the Agreement;

         WHEREAS, each of the parties hereto is a party to an Amendment No. 1 to
the Agreement dated as of October 20, 1998 ("Amendment No. 1"); and

         WHEREAS, each of META, Acquisition Sub and SENTRY desires to further
amend the Agreement as set forth below;

         NOW, THEREFORE, in consideration of these premises and the mutual
agreements contained in this Amendment, in accordance with Sections 10.6 and
10.7 of the Agreement each of META, Acquisition Sub and SENTRY hereby agrees as
follows:

                                    ARTICLE I

                               CERTAIN AGREEMENTS

         1.1 CONTINGENT CONSIDERATION. Notwithstanding any other provision of
the Agreement, each of the parties hereto hereby agrees that:

         (i) the Contingent Consideration set forth in Section 2.3(e)(i)(A) of
the Agreement shall be due and payable as of the date hereof in accordance with
the provisions of this Amendment;

         (ii) for the purposes of Article IX of the Agreement, the Contingent
Closing Date shall be deemed to have occurred on the day after the date hereof;
and

         (iii) the payment of such Contingent Consideration shall be made solely
in META Common (and cash in lieu of fractional shares) to the persons/entities
on the attached EXHIBIT A in the share number and cash amount set forth opposite
such person's/entities' name (and each party hereto agrees that such payment
shall fully and unconditionally satisfy all of META and SENTRY's obligations
hereunder and under the Agreement with respect to the payment of Contingent
Consideration).

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         1.2 WAIVER OF REMEDIES AND RELEASE. Notwithstanding any other provision
of the Agreement, Sentry and the undersigned Stockholder Representative on
behalf of the Former Sentry Holders hereby irrevocably waive any and all rights
and remedies with respect to any other party's failure to comply with the
provisions of the Agreement relating to Contingent Consideration (other than the
payment obligation set forth in Section 1.1 of this Amendment) and hereby
irrevocably waives such compliance. In addition, the undersigned Stockholder
Representative hereby agrees to execute a release in the form attached as
EXHIBIT B on behalf of the Former Sentry Holders.

         1.3 WITHHOLDING RIGHTS. META, SENTRY and Acquisition Sub shall be
entitled to deduct and withhold from the consideration otherwise payable
pursuant to this Amendment such amounts as META, SENTRY or Acquisition Sub
determine they are required to deduct and withhold with respect to the making of
such payment under the Internal Revenue Code, or any provision of state, local,
or foreign tax law. To the extent that amounts are so withheld, such withheld
amounts shall be treated for all purposes hereof as having been paid to the
holder of the shares in respect of which such deduction and withholding was
made. To the extent that the amount so required to be deducted or withheld from
any payment to a holder exceeds the cash portion of the consideration otherwise
payable to the holder, META, SENTRY and Acquisition Sub are hereby authorized to
sell or otherwise dispose of at fair market value such portion of such
consideration as is necessary to provide sufficient funds to META, SENTRY or
Acquisition Sub, as the case may be, in order to enable it to comply with such
deduction or withholding requirement.

         1.4 NO THIRD PARTY BENEFICIARY RIGHTS. No provision of this Amendment
shall create any third party beneficiary or other rights in any person or entity
not a party hereto.

                                   ARTICLE II

                                  MISCELLANEOUS

         2.1 RATIFICATION/CONFIRMATION OF AGREEMENT. Except as set forth in
Amendment No. 1 or as herein expressly amended, the Agreement is ratified and
confirmed in all respects and shall remain in full force and effect in
accordance with its terms.

         2.2 DEFINITIONS. Capitalized terms used herein without definition shall
have the respective meanings ascribed to such terms in the Agreement.

         2.3 ASSIGNMENT. Neither this Amendment nor any of the rights, interests
or obligations under this Amendment shall be assigned by any of the parties
without the prior written consent of the other parties.

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         2.4 HEADINGS AND CAPTIONS. The headings and captions in this Amendment
are for convenience and reference purposes only and shall not be considered a
part of or affect the construction or interpretation of any provision of this
Amendment.

         2.5 SUCCESSORS AND ASSIGNS. This Amendment shall be binding upon, inure
to the benefit of and may be enforced by, each of the parties to this Amendment
and their successors and assigns.

         2.6 GOVERNING LAW. This Amendment shall be governed by and construed,
interpreted, and enforced in accordance with the laws of the Commonwealth of
Massachusetts, without giving effect to the principles of conflicts of law
thereof.

         2.7 COUNTERPARTS; FACSIMILE SIGNATURES. This Amendment may be executed
simultaneously in one or more counterparts, each of which shall be deemed to be
an original but all of which together shall constitute one and the same
instrument. For the purposes of executing this Amendment, (a) a document signed
and transmitted by facsimile machine or telecopier shall be treated as an
original document; (b) the signature of any party on such document shall be
considered as an original signature; (c) the document transmitted (or the
document of which the page containing the signature or signatures of one of more
parties is transmitted) shall have the same effect as a counterpart thereof
containing original signatures; and (d) at the request of a party, each party
who executed a document and transmitted such document by facsimile machine or
telecopier, shall provide such original document to the other party. No party
may raise as a defense to the enforcement of this Amendment, that a facsimile
machine or telecopier was used to transmit a signature of that party or another
party on the Amendment.

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         IN WITNESS WHEREOF, each of META, Acquisition Sub and Sentry have
caused this Amendment to be duly executed and delivered as of May 12, 2000.

                                      META GROUP, INC.

                                      By: /s/ BERNARD DENOYER
                                         -------------------------------
                                         Name:  Bernard Denoyer
                                         Title: CFO


                                      MG ACQUISITION CORPORATION

                                      By: /s/ BERNARD DENOYER
                                         -------------------------------
                                         Name:  Bernard Denoyer
                                         Title: CFO


                                      THE SENTRY GROUP, INC.

                                      By: /s/ BERNARD DENOYER
                                         -------------------------------
                                         Name:  Bernard Denoyer
                                         Title: CFO



Agreed and accepted to:

/s/ PETER A. NABER
----------------------------------
Peter A. Naber, as
Stockholder Representative on behalf
of the Former Sentry Holders