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                                                                  EXECUTION COPY

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                           IRON MOUNTAIN INCORPORATED

                                      AND

                             THE BANK OF NEW YORK,
                                   as Trustee

                    8 5/8% Senior Subordinated Notes due 2013

                          FIRST SUPPLEMENTAL INDENTURE

                           Dated as of April 3, 2001

                                       TO

                             SUBORDINATED INDENTURE

                           Dated as of April 3, 2001

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                                TABLE OF CONTENTS

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ARTICLE 1. DEFINITIONS.........................................................1

   Section 1.1.    Definitions.................................................1

ARTICLE 2. FORM AND TERMS OF THE NOTES........................................19

   Section 2.1.    Form and Dating............................................19
   Section 2.2.    Execution and Authentication...............................20
   Section 2.3.    Depository and Paying Agent for Notes......................20
   Section 2.4.    Transfer and Exchange of Notes.............................20
   Section 2.5.    Redemption.................................................22
   Section 2.6.    Covenants..................................................25
      (a)  Reports............................................................25
      (b)  Restricted Payments................................................25
      (c)  Incurrence of Indebtedness and Issuance of Preferred Stock.........28
      (d)  Liens..............................................................29
      (e)  Dividend and Other Payment Restrictions Affecting Restricted
           Subsidiaries.......................................................29
      (f)  Transactions with Affiliates.......................................31
      (g)  Certain Senior Subordinated Debt...................................32
      (h)  Additional Subsidiary Guarantees...................................32
      (i)  Designation of Unrestricted Subsidiaries...........................33
      (j)  Limitation on Sale and Leaseback Transactions......................34
      (k)  Asset Sales........................................................35
      (l)  Change of Control Offer............................................37
      (m)  Corporate Existence................................................38
   Section 2.7.    Mergers, Consolidations or Sale of Assets..................39
   Section 2.8.    Events of Default..........................................40
   Section 2.9.    Acceleration...............................................41
   Section 2.10.   Amendments and Waivers.....................................42
   Section 2.11.   Subsidiary Guarantees......................................45
   Section 2.12.   Legal Defeasance and Covenant Defeasance...................45
   Section 2.13    Subordination..............................................45

ARTICLE 3. MISCELLANEOUS......................................................46

   Section 3.1.    Effect of Headings.........................................46
   Section 3.2.    Successors and Assigns.....................................46
   Section 3.3.    Separability Clause........................................47
   Section 3.4.    Governing Law..............................................47
   Section 3.5     First Supplement to Supersede Indenture....................47

EXHIBITS

Exhibit A         FORM OF NOTES
Exhibit B         FORM OF SUPPLEMENTAL INDENTURE
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            THIS FIRST SUPPLEMENTAL INDENTURE, dated as of April 3, 2001 ("First
Supplemental Indenture"), is by and among IRON MOUNTAIN INCORPORATED, a
Pennsylvania corporation, having its principal office at 745 Atlantic Avenue,
Boston, Massachusetts 02111, the Guarantors signatory hereto and THE BANK OF NEW
YORK, a New York banking corporation, as trustee, having its principal corporate
trust office at 101 Barclay Street, 21st Floor, New York, NY 10286.

                                   WITNESSETH:

            WHEREAS, the Company and The Bank of New York, acting as trustee,
executed and delivered a Subordinated Indenture, dated as of April 3, 2001 (the
"Indenture"), to provide for the issuance by the Company from time to time of
Securities to be issued in one or more series as provided in the Indenture;

            WHEREAS, the issuance and sale of up to $500,000,000 aggregate
principal amount of a series of the Company's Securities (the "Notes") have been
authorized by resolutions adopted by the Board of Directors of the Company on
March 6, 2001;

            WHEREAS, the Company desires to issue and sell $225,000,000
aggregate principal amount of the Notes on the date hereof;

            WHEREAS, the Company desires to enter into this First Supplemental
Indenture pursuant to Section 9.1(e) of the Indenture to supplement the
Indenture to establish the form and terms of the Notes; and

            NOW, THEREFORE, for and in consideration of the premises stated
herein and the purchase of the Notes by the Holders thereof, the parties hereto
hereby enter into this First Supplemental Indenture, for the equal and
proportionate benefit of all Holders of Notes, as follows:

                                   ARTICLE 1.

                                   DEFINITIONS

Section 1.1. Definitions.

            (a) All of the terms used in this First Supplemental Indenture which
are defined in the Indenture shall have the meanings specified in the Indenture,
unless otherwise defined herein (in which case they shall have the meanings
defined herein for the purposes of the Indenture as well as for the First
Supplemental Indenture) or unless the context otherwise requires, and for the
purposes of this First Supplemental Indenture, the following terms have the
meanings set forth in this Section:

            "Acquired Debt" means, with respect to any specified Person:

            (1)   Indebtedness of any other Person, existing at the time such
                  other Person merged with or into or became a Subsidiary of
                  such specified Person, including Indebtedness incurred in
                  connection with, or in contemplation of, such other Person
                  merging with or into or becoming a Subsidiary of such
                  specified Person and

            (2)   Indebtedness encumbering any asset acquired by such specified
                  Person.

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            "Acquisition EBITDA" means, as of any date of determination, with
respect to an Acquisition EBITDA Entity, the sum of:

            (1)   EBITDA of such Acquisition EBITDA Entity for its last fiscal
                  quarter for which financial statements are available at such
                  date of determination (adjusted to give pro forma effect to
                  any acquisition or disposition of a business or Person by such
                  Acquisition EBITDA Entity consummated during the period
                  covered by, or after the date of, such quarterly financial
                  statements), multiplied by four (or if such quarterly
                  statements are not available, EBITDA for the most recent
                  fiscal year for which financial statements are available),
                  plus

            (2)   projected quantifiable improvements in operating results (on
                  an annualized basis) due to cost reductions calculated in good
                  faith by the Company or one of its Restricted Subsidiaries, as
                  certified by an Officers' Certificate filed with the Trustee,
                  without giving effect to any operating losses of the acquired
                  Person.

            "Acquisition EBITDA Entity" means, as of any date of determination,
a business or Person:

            (1)   which has been acquired by the Company or one of its
                  Restricted Subsidiaries and with respect to which financial
                  results on a consolidated basis with the Company have not been
                  made available for an entire fiscal quarter or

            (2)   which is to be acquired in whole or in part with Indebtedness,
                  the incurrence of which will require the calculation on such
                  date of the Acquisition EBITDA of such Acquisition EBITDA
                  Entity for purposes of Section 4.8 of the Indenture.

                  "Additional Notes" means up to $275,000,000 aggregate
principal amount of the Company's 8 5/8% Senior Subordinated Notes due 2013
(other than the Initial Notes) issued under this First Supplemental Indenture in
accordance with Section 2.2 hereof as part of the same series as the Initial
Notes.

            "Adjusted EBITDA" means, as of any date of determination and without
duplication, the sum of:

            (1)   EBITDA of the Company and its Restricted Subsidiaries for the
                  most recent fiscal quarter for which internal financial
                  statements are available at such date of determination,
                  multiplied by four and

            (2)   Acquisition EBITDA of each business or Person that is an
                  Acquisition EBITDA Entity as of such date of determination,
                  multiplied by a fraction, (i) the numerator of which is three
                  minus the number of months (and/or any portion thereof) in
                  such most recent fiscal quarter for which the financial
                  results of such Acquisition EBITDA Entity are included in the
                  EBITDA of the Company and its Restricted Subsidiaries under
                  clause (1) above, and (ii) the denominator of which is three.


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The effects of unusual items, including merger-related expenses permitted to be
shown as a separate line item on a statement of operations in accordance with
GAAP, or non-recurring items in respect of the Company, a Restricted Subsidiary
or an Acquisition EBITDA Entity occurring in any period shall be excluded in the
calculation of Adjusted EBITDA.

            "Affiliate" of any specified Person means any other Person directly
or indirectly controlling or controlled by or under direct or indirect common
control with such specified Person. For purposes of this definition, "control"
(including, with correlative meanings, the terms "controlling," "controlled by"
and "under common control with"), as used with respect to any Person, shall mean
the possession, directly or indirectly, of the power to direct or cause the
direction of the management or policies of such Person, whether through the
ownership of voting securities, by agreement or otherwise; provided, however,
that beneficial ownership of 10% or more of the voting securities of a Person
shall be deemed to be control.

            "Agent Members" means members of, or participants in, the
Depository.

            "Attributable Indebtedness" in respect of a Sale and Leaseback
Transaction means, as of the time of determination, the greater of:

            (1)   the fair market value of the property subject to such
                  arrangement (as determined by the Board of Directors of the
                  Company) and

            (2)   the present value (discounted at the rate of interest implicit
                  in such transaction) of the total obligations of the lessee
                  for rental payments during the remaining terms of the lease
                  included in such Sale and Leaseback Transaction (including any
                  period for which such lease has been extended).

            "Capital Lease Obligation" means, at the time any determination
thereof is to be made, the amount of the liability in respect of a capital lease
that would at such time be so required to be capitalized on the balance sheet in
accordance with GAAP.

            "Capital Stock" means any and all shares, interests, participations,
rights or other equivalents (however designated) of corporate stock, including,
without limitation, with respect to partnerships, partnership interests (whether
general or limited) and any other interest or participation that confers on a
Person the right to receive a share of the profits and losses of, or
distributions of assets of, such partnership.

            "Cash Equivalents" means:

            (1)   securities with maturities of one year or less from the date
                  of acquisition, issued, fully guaranteed or insured by the
                  United States Government or any agency thereof;

            (2)   certificates of deposit, time deposits, overnight bank
                  deposits, bankers acceptances and repurchase agreements issued
                  by a Qualified Issuer having maturities of 270 days or less
                  from the date of acquisition;


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            (3)   commercial paper of an issuer rated at least A-2 by Standard &
                  Poor's Rating Group, a division of McGraw Hill, Inc., or P-2
                  by Moody's Investors Service, or carrying an equivalent rating
                  by a nationally recognized rating agency if both of the two
                  named rating agencies cease publishing ratings of investments
                  and having maturities of 270 days or less from the date of
                  acquisition;

            (4)   money market accounts or funds with or issued by Qualified
                  Issuers; and

            (5)   Investments in money market funds substantially all of the
                  assets of which are comprised of securities and other
                  obligations of the types described in clauses (1) through (3)
                  above.

            "Change of Control" means the occurrence of any of the following
events:

            (1)   any "person" or "group" (as such terms are used in Sections
                  13(d) and 14(d) of the Exchange Act), other than the Principal
                  Stockholders (or any of them), is or becomes the "beneficial
                  owner" (as defined in Rules 13d-3 and 13d-5 under the Exchange
                  Act), directly or indirectly, of more than a majority of the
                  voting power of all classes of Voting Stock of the Company;

            (2)   the Company consolidates with, or merges with or into, another
                  Person or conveys, transfers, leases or otherwise disposes of
                  all or substantially all of its assets to any Person, or any
                  Person consolidates with, or merges with or into, the Company,
                  in any such event pursuant to a transaction in which the
                  outstanding Voting Stock of the Company is converted into or
                  exchanged for cash, securities or other property, other than
                  any such transaction where (i) the outstanding Voting Stock of
                  the Company is not converted or exchanged at all (except to
                  the extent necessary to reflect a change in the jurisdiction
                  of incorporation) or is converted into or exchanged for (A)
                  Voting Stock (other than Disqualified Stock) of the surviving
                  or transferee Person or (B) cash, securities and other
                  property (other than Capital Stock described in the foregoing
                  clause (A)) of the surviving or transferee Person in an amount
                  that could be paid as a Restricted Payment pursuant to Section
                  2.6(b) of this First Supplemental Indenture (Section 4.7 of
                  the Indenture) and (ii) immediately after such transaction, no
                  "person" or "group" (as such terms are used in Sections 13(d)
                  and 14(d) of the Exchange Act), other than the Principal
                  Stockholders (or any of them), is the "beneficial owner" (as
                  defined in Rules 13d-3 and 13d-5 under the Exchange Act),
                  directly or indirectly, of more than a majority of the total
                  outstanding Voting Stock of the surviving or transferee
                  Person;

            (3)   during any consecutive two-year period, individuals who at the
                  beginning of such period constituted the Board of Directors
                  (together with any new directors whose election to such Board
                  of Directors, or whose nomination for election by the
                  stockholders of the Company, was approved by a vote of 66 2/3%
                  of the directors then still in office who were either
                  directors at the beginning of such period or whose election or
                  nomination for election was previously so approved)


                                       4
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                  cease for any reason to constitute a majority of the Board of
                  Directors then in office; or

            (4)   the Company is liquidated or dissolved or adopts a plan of
                  liquidation or dissolution other than in a transaction which
                  complies with Section 2.7 of the First Supplemental Indenture
                  (Section 5.1 of the Indenture).

            "Consolidated Adjusted Net Income" means, for any period, the net
income (or net loss) of the Company and its Restricted Subsidiaries for such
period as determined on a consolidated basis in accordance with GAAP, adjusted
to the extent included in calculating such net income or loss by excluding:

            (1)   any net after-tax extraordinary gains or losses (less all fees
                  and expenses relating thereto);

            (2)   any net after-tax gains or losses (less all fees and expenses
                  relating thereto) attributable to Asset Sales;

            (3)   the portion of net income (or loss) of any Person (other than
                  the Company or a Restricted Subsidiary), including
                  Unrestricted Subsidiaries, in which the Company or any
                  Restricted Subsidiary has an ownership interest, except to the
                  extent of the amount of dividends or other distributions
                  actually paid to the Company or any Restricted Subsidiary in
                  cash dividends or distributions by such Person during such
                  period; and

            (4)   the net income (or loss) of any Person combined with the
                  Company or any Restricted Subsidiary on a "pooling of
                  interests" basis attributable to any period prior to the date
                  of combination.

            "Consolidated Income Tax Expense" means, for any period, the
provision for federal, state, local and foreign income taxes of the Company and
its Restricted Subsidiaries for such period as determined on a consolidated
basis in accordance with GAAP.

            "Consolidated Interest Expense" means, for any period, without
duplication, the sum of:

            (1)   the amount which, in conformity with GAAP, would be set forth
                  opposite the caption "interest expense" (or any like caption)
                  on a consolidated statement of operations of the Company and
                  its Restricted Subsidiaries for such period, including,
                  without limitation:

                  (i)   amortization of debt discount;

                  (ii)  the net cost of interest rate contracts (including
                        amortization of discounts);

                  (iii) the interest portion of any deferred payment obligation;

                  (iv)  amortization of debt issuance costs; and


                                       5
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                  (v)   the interest component of Capital Lease Obligations of
                        the Company and its Restricted Subsidiaries; plus

            (2)   all interest on any Indebtedness of any other Person
                  guaranteed and paid by the Company or any of its Restricted
                  Subsidiaries;

provided, however, that Consolidated Interest Expense will not include any gain
or loss from extinguishment of debt, including write-off of debt issuance costs.

            "Consolidated Non-Cash Charges" means, for any period, the aggregate
depreciation, amortization and other non-cash expenses of the Company and its
Restricted Subsidiaries (including without limitation any minority interest)
reducing Consolidated Adjusted Net Income for such period, determined on a
consolidated basis in accordance with GAAP (excluding any such non-cash charge
to the extent that it requires an accrual of or reserve for cash charges for any
future period).

            "Credit Agent" means The Chase Manhattan Bank, in its capacity as
administrative agent for the lenders party to the Credit Agreement, and The
Chase Manhattan Bank Canada, in its capacity as Canadian administrative agent
for the lenders party to the Credit Agreement, or any successor or successors
party thereto.

            "Credit Agreement" means that certain Fourth Amended and Restated
Credit Agreement dated as of August 14, 2000, as amended, among the Company, IM
Canada, the lenders party thereto and the Credit Agent, as further amended,
restated, supplemented, modified, renewed, refunded, increased, extended,
replaced or refinanced from time to time.

            "Default" means any event that is or with the passage of time or the
giving of notice or both would be an Event of Default.

            "Definitive Notes" means Notes that are in the form of the Notes
attached hereto as Exhibit A, that do not include the information called for by
Section 2.15 of the Indenture.

            "Designated Senior Debt" means:

            (1)   Senior Bank Debt and

            (2)   other Senior Debt the principal amount of which is $50.0
                  million or more at the date of designation by the Company in a
                  written instrument delivered to the Trustee.

Senior Debt designated as Designated Senior Debt pursuant to clause (2) shall
cease to be Designated Senior Debt at any time that the aggregate principal
amount thereof outstanding is $10.0 million or less.

            "Disqualified Stock" means any Capital Stock which, by its terms (or
by the terms of any security into which it is convertible or for which it is
exchangeable), or upon the happening of any event, matures or is mandatorily
redeemable, for cash or other property (other than Capital Stock that is not
Disqualified Stock) pursuant to a sinking fund obligation or otherwise, or is
redeemable at the option of the Holder thereof, in whole or in part, in each
case on or prior to the stated maturity of the Notes.


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            "Dollars" and "$" mean lawful money of the United States of America.

            "EBITDA" means for any period Consolidated Adjusted Net Income for
such period increased by:

            (1)   Consolidated Interest Expense for such period; plus

            (2)   Consolidated Income Tax Expense for such period; plus

            (3)   Consolidated Non-Cash Charges for such period.

            "Equity Interests" means Capital Stock and all warrants, options or
other rights to acquire Capital Stock (but excluding any debt security that is
convertible into, or exchangeable for, Capital Stock).

            "Equity Proceeds" means:

            (1)   with respect to Equity Interests (or debt securities converted
                  into Equity Interests) issued or sold for cash Dollars, the
                  aggregate amount of such cash Dollars and

            (2)   with respect to Equity Interests (or debt securities converted
                  into Equity Interests) issued or sold for any consideration
                  other than cash Dollars, the aggregate Market Price thereof
                  computed on the date of the issuance or sale thereof.

            "Excluded Restricted Subsidiary" means any Restricted Subsidiary
organized under the laws of a jurisdiction other than the United States (as
defined in Regulation S under the Securities Act) and that has not delivered a
Subsidiary Guarantee.

            "Existing Indebtedness" means Indebtedness of the Company and its
Subsidiaries (other than under the Credit Agreement) in existence on the date of
the Indenture, until such amounts are repaid.

            "Global Note" means a permanent global Note that contains the
paragraph referred to in Section 2.15 of the Indenture and the additional
Schedule of Exchanges of Notes to the form of the Note attached hereto as
Exhibit A, and that is deposited with and registered in the name of the
Depository.

            "Government Securities" means direct obligations of, or obligations
guaranteed by, the United States of America for the payment of which guarantee
or obligations the full faith and credit of the United States of America is
pledged.

            "Guarantee" means, as applied to any obligation:

            (1)   a guarantee (other than by endorsement of negotiable
                  instruments for collection in the ordinary course of
                  business), direct or indirect, in any manner, of any part or
                  all of such obligation; and


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            (2)   an agreement, direct or indirect, contingent or otherwise, the
                  practical effect of which is to assure in any way the payment
                  or performance (or payment of damages in the event of
                  non-performance) of all or any part of such obligation,
                  including, without limiting the foregoing, the obligation to
                  reimburse amounts drawn down under letters of credit securing
                  such obligations.

            "Hedging Obligations" means, with respect to any Person, the
obligations of such Person under:

            (1)   interest rate swap agreements, interest rate cap agreements
                  and interest rate collar agreements and

            (2)   other agreements or arrangements designed to protect such
                  Person against fluctuations in interest rates.

            "IM Canada" means Iron Mountain Canada Corporation, a Wholly Owned
Subsidiary of the Company, formerly known as Pierce Leahy Canada Company.

            "Indebtedness" means (without duplication), with respect to any
Person, whether recourse is to all or a portion of the assets of such Person,
and whether or not contingent:

            (1)   every obligation of such Person for money borrowed;

            (2)   every obligation of such Person evidenced by bonds,
                  debentures, notes or other similar instruments;

            (3)   every reimbursement obligation of such Person with respect to
                  letters of credit, bankers' acceptances or similar facilities
                  issued for the account of such Person;

            (4)   every obligation of such Person issued or assumed as the
                  deferred purchase price of property or services;

            (5)   every Capital Lease Obligation and every obligation of such
                  Person in respect of Sale and Leaseback Transactions that
                  would be required to be capitalized on the balance sheet in
                  accordance with GAAP;

            (6)   all Disqualified Stock of such Person valued at the greater of
                  its voluntary or involuntary maximum fixed repurchase price,
                  plus accrued and unpaid dividends (unless included in such
                  maximum repurchase price);

            (7)   all obligations of such Person under or with respect to
                  Hedging Obligations which would be required to be reflected on
                  the balance sheet as a liability of such Person in accordance
                  with GAAP; and

            (8)   every obligation of the type referred to in clauses (1)
                  through (7) of another Person and dividends of another Person
                  the payment of which, in either case, such Person has
                  guaranteed.


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            For purposes of this definition, the "maximum fixed repurchase
price" of any Disqualified Stock that does not have a fixed repurchase price
shall be calculated in accordance with the terms of such Disqualified Stock as
if such Disqualified Stock were repurchased on any date on which Indebtedness is
required to be determined pursuant to the First Supplemental Indenture, and if
such price is based upon, or measured by, the fair market value of such
Disqualified Stock, such fair market value shall be determined in good faith by
the board of directors of the issuer of such Disqualified Stock. Notwithstanding
the foregoing, trade accounts payable and accrued liabilities arising in the
ordinary course of business and any liability for federal, state or local taxes
or other taxes owed by such Person shall not be considered Indebtedness for
purposes of this definition. The amount outstanding at any time of any
Indebtedness issued with original issue discount is the aggregate principal
amount at maturity of such Indebtedness, less the remaining unamortized portion
of the original issue discount of such Indebtedness at such time, as determined
in accordance with GAAP.

            "Initial Notes" means the first $225,000,000 aggregate principal
amount of 8 5/8% Senior Subordinated Notes due 2013 that are issued under the
First Supplemental Indenture, as amended or supplemented from time to time
pursuant to the Indenture.

            "Investments" means, with respect to any Person, all investments by
such Person in other Persons (including Affiliates) in the forms of loans
(including Guarantees), advances or capital contributions (excluding commission,
travel and similar advances to officers and employees made in the ordinary
course of business), purchases or other acquisitions for consideration of
Indebtedness, Equity Interests or other securities and all other items that are
or would be classified as investments on a balance sheet prepared in accordance
with GAAP.

            "Leverage Ratio" means, at any date, the ratio of:

            (1)   the aggregate principal amount of Indebtedness of the Company
                  and its Restricted Subsidiaries outstanding as of the most
                  recent available quarterly or annual balance sheet, to

            (2)   Adjusted EBITDA, after giving pro forma effect, without
                  duplication, to

                  (i)   the incurrence, repayment or retirement of any
                        Indebtedness by the Company or its Restricted
                        Subsidiaries since the last day of the most recent full
                        fiscal quarter of the Company;

                  (ii)  if the Leverage Ratio is being determined in connection
                        with the incurrence of Indebtedness by the Company or a
                        Restricted Subsidiary, such Indebtedness; and

                  (iii) the Indebtedness to be incurred in connection with the
                        acquisition of any Acquisition EBITDA Entity.

            "Lien" means, with respect to any asset, any mortgage, lien, pledge,
charge, security interest or encumbrance of any kind in respect of such asset,
whether or not filed, recorded or otherwise perfected under applicable law
(including any conditional sale or other title retention agreement, any lease in
the nature thereof, any option or other agreement to sell or give a security
interest in and any


                                       9
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filing of or agreement to give any financing statement under the Uniform
Commercial Code, or equivalent statutes, of any jurisdiction).

            "Make-Whole Amount" means, with respect to any Note, an amount equal
to the excess, if any, of:

            (1)   the present value of the remaining principal, premium and
                  interest payments that would be payable with respect to such
                  Note if such Note were redeemed on April 1, 2006, computed
                  using a discount rate equal to the Treasury Rate plus 75 basis
                  points over

            (2)   the outstanding principal amount of such Note.

            "Make-Whole Average Life" means, with respect to any date of
redemption of Notes, the number of years (calculated to the nearest one-twelfth)
from such redemption date to April 1, 2006.

            "Make-Whole Price" means, with respect to any Note, the greater of:

            (1)   the sum of the principal amount of and Make-Whole Amount with
                  respect to such Note and

            (2)   the redemption price of such Note on April 1, 2006.

            "Market Price" means:

            (1)   with respect to the calculation of Equity Proceeds from the
                  issuance or sale of debt securities which have been converted
                  into Equity Interests, the value received upon the original
                  issuance or sale of such converted debt securities, as
                  determined reasonably and in good faith by the Board of
                  Directors and

            (2)   with respect to the calculation of Equity Proceeds from the
                  issuance or sale of Equity Interests, the average of the daily
                  closing prices for such Equity Interests for the 20
                  consecutive trading days preceding the date of such
                  computation.

            The closing price for each day shall be:

            (1)   if such Equity Interests are then listed or admitted to
                  trading on the New York Stock Exchange, the closing price on
                  the NYSE Consolidated Tape (or any successor consolidated tape
                  reporting transactions on the New York Stock Exchange) or, if
                  such composite tape shall not be in use or shall not report
                  transactions in such Equity Interests, or if such Equity
                  Interests shall be listed on a stock exchange other than the
                  New York Stock Exchange (including for this purpose the Nasdaq
                  National Market), the last reported sale price regular way for
                  such day, or in case no such reported sale takes place on such
                  day, the average of the closing bid and asked prices regular
                  way for such day, in each case on the principal national
                  securities exchange on which such Equity Interests are listed
                  or admitted to trading (which shall be the national securities
                  exchange on which the


                                       10
<PAGE>

                  greatest number of such Equity Interests have been traded
                  during such 20 consecutive trading days); or

            (2)   if such Equity Interests are not listed or admitted to trading
                  on any such exchange, the average of the closing bid and asked
                  prices thereof in the over-the-counter market as reported by
                  the National Association of Securities Dealers Automated
                  Quotation System or any successor system, or if not included
                  therein, the average of the closing bid and asked prices
                  thereof furnished by two members of the National Association
                  of Securities Dealers selected reasonably and in good faith by
                  the Board of Directors for that purpose. In the absence of one
                  or more such quotations, the Market Price for such Equity
                  Interests shall be determined reasonably and in good faith by
                  the Board of Directors.

            "Net Proceeds" means the aggregate cash proceeds received by the
Company or any of its Restricted Subsidiaries in respect of any Asset Sale,
which amount is equal to the excess, if any, of:

            (1)   the cash received by the Company or such Restricted Subsidiary
                  (including any cash payments received by way of deferred
                  payment pursuant to, or monetization of, a note or installment
                  receivable or otherwise, but only as and when received) in
                  connection with such disposition, over

            (2)   the sum of:

                  (i)   the amount of any Indebtedness which is secured by such
                        asset and which is required to be repaid in connection
                        with the disposition thereof; plus

                  (ii)  the reasonable out-of-pocket expenses incurred by the
                        Company or such Restricted Subsidiary, as the case may
                        be, in connection with such disposition or in connection
                        with the transfer of such amount from such Restricted
                        Subsidiary to the Company; plus

                  (iii) provisions for taxes, including income taxes,
                        attributable to the disposition of such asset or
                        attributable to required prepayments or repayments of
                        Indebtedness with the proceeds thereof; plus

                  (iv)  if the Company does not first receive a transfer of such
                        amount from the relevant Restricted Subsidiary with
                        respect to the disposition of an asset by such
                        Restricted Subsidiary and such Restricted Subsidiary
                        intends to make such transfer as soon as practicable,
                        the out-of-pocket expenses and taxes that the Company
                        reasonably estimates will be incurred by the Company or
                        such Restricted Subsidiary in connection with such
                        transfer at the time such transfer is expected to be
                        received by the Company (including, without limitation,
                        withholding taxes on the remittance of such amount).


                                       11
<PAGE>

            "Notes" has the meaning assigned to it in the preamble to this First
Supplemental Indenture. The Initial Notes and any Additional Notes shall be
treated as a single class for all purposes under this First Supplemental
Indenture and the Indenture.

            "Obligations" means any principal, interest (including post-petition
interest, whether or not allowed as a claim in any proceeding), penalties, fees,
costs, expenses, indemnifications, reimbursements, damages and other liabilities
payable under or in connection with any Indebtedness.

            "Officers' Certificate" means a certificate signed, unless otherwise
specified, by any two of the Chairman of the Board, a Vice Chairman of the
Board, the President, the Chief Financial Officer, the Controller, or an
Executive Vice President of the Company, and delivered to the Trustee.

            "Permitted Investments" means:

            (1)   any Investments in the Company or in a Restricted Subsidiary
                  (other than an Excluded Restricted Subsidiary) of the Company,
                  including without limitation the Guarantee of Indebtedness
                  permitted under Section 2.6(c) of the First Supplemental
                  Indenture (Section 4.8 of the Indenture);

            (2)   any Investments in Cash Equivalents;

            (3)   Investments by the Company or any Restricted Subsidiary of the
                  Company in a Person, if as a result of such Investment;

                  (i)   such Person becomes a Restricted Subsidiary (other than
                        an Excluded Restricted Subsidiary) of the Company or

                  (ii)  such Person is merged, consolidated or amalgamated with
                        or into, or transfers or conveys substantially all of
                        its assets to, or is liquidated into, the Company or a
                        Restricted Subsidiary (other than an Excluded Restricted
                        Subsidiary) of the Company;

            (4)   Investments in assets (including accounts and notes
                  receivable) owned or used in the ordinary course of business;

            (5)   Investments for any purpose related to the Company's records
                  and information management business (including, without
                  limitation, the Company's confidential destruction and
                  fulfillment businesses) in an aggregate outstanding amount not
                  to exceed $10.0 million; and

            (6)   Investments by the Company or a Restricted Subsidiary (other
                  than an Excluded Restricted Subsidiary) in one or more
                  Excluded Restricted Subsidiaries, the aggregate outstanding
                  amount of which does not exceed 10% of the consolidated assets
                  of the Company and its Restricted Subsidiaries.

            "Permitted Liens" means:

            (1)   Liens existing as of the date hereof;


                                       12
<PAGE>

            (2)   Liens on property or assets of the Company or any Restricted
                  Subsidiary securing Senior Debt;

            (3)   Liens on any property or assets of a Restricted Subsidiary
                  granted in favor of the Company or any Wholly Owned Restricted
                  Subsidiary;

            (4)   Liens securing the Notes or the Guarantees;

            (5)   any interest or title of a lessor under any Capital Lease
                  Obligation or Sale and Leaseback Transaction so long as the
                  Indebtedness, if any, secured by such Lien does not exceed the
                  principal amount of Indebtedness permitted under Section
                  2.6(c) of the First Supplemental Indenture (Section 4.8 of the
                  Indenture);

            (6)   Liens securing Acquired Debt created prior to (and not in
                  connection with or in contemplation of) the incurrence of such
                  Indebtedness by the Company or any Restricted Subsidiary;
                  provided that such Lien does not extend to any property or
                  assets of the Company or any Restricted Subsidiary other than
                  the assets acquired in connection with the incurrence of such
                  Acquired Debt;

            (7)   Liens securing Hedging Obligations permitted to be incurred
                  pursuant to clause (7) of Section 2.6(c) of the First
                  Supplemental Indenture (clause (7) of Section 4.8 of the
                  Indenture);

            (8)   Liens arising from purchase money mortgages and purchase money
                  security interests, or in respect of the construction of
                  property or assets, incurred in the ordinary course of the
                  business of the Company or a Restricted Subsidiary; provided
                  that (i) the related Indebtedness is not secured by any
                  property or assets of the Company or any Restricted Subsidiary
                  other than the property and assets so acquired or constructed
                  and (ii) the Lien securing such Indebtedness is created within
                  60 days of such acquisition or construction;

            (9)   statutory Liens or landlords' and carriers', warehousemen's,
                  mechanics', suppliers', materialmen's, repairmen's or other
                  like Liens arising in the ordinary course of business and with
                  respect to amounts not yet delinquent or being contested in
                  good faith by appropriate proceedings, if a reserve or other
                  appropriate provision, if any, as is then required in
                  conformity with GAAP shall have been made therefor;

            (10)  Liens for taxes, assessments, government charges or claims
                  with respect to amounts not yet delinquent or that are being
                  contested in good faith by appropriate proceedings diligently
                  conducted, if a reserve or other appropriate provision, if
                  any, as is required in conformity with GAAP has been made
                  therefor;

            (11)  Liens incurred or deposits made to secure the performance of
                  tenders, bids, leases, statutory obligations, surety and
                  appeal bonds, government contracts, performance bonds and
                  other obligations of a like nature incurred in the ordinary
                  course of business (other than contracts for the payment of
                  money);


                                       13
<PAGE>

            (12)  easements, rights-of-way, restrictions and other similar
                  charges or encumbrances not interfering in any material
                  respect with the business of the Company or any Restricted
                  Subsidiary incurred in the ordinary course of business;

            (13)  Liens arising by reason of any judgment, decree or order of
                  any court so long as such Lien is adequately bonded and any
                  appropriate legal proceedings that may have been duly
                  initiated for the review of such judgment, decree or order
                  shall not have been finally terminated or the period within
                  which such proceedings may be initiated shall not have
                  expired;

            (14)  Liens arising under options or agreements to sell assets;

            (15)  other Liens securing obligations incurred in the ordinary
                  course of business, which obligations do not exceed $10.0
                  million in the aggregate at any one time outstanding; and

            (16)  any extension, renewal or replacement, in whole or in part, of
                  any Lien described in the foregoing clauses (1) through (15);
                  provided that any such extension, renewal or replacement shall
                  not extend to any additional property or assets.

            "Person" means any individual, corporation, limited liability
company, partnership, joint venture, association, joint-stock company, trust,
unincorporated organization or government or any agency or political subdivision
thereof.

            "Principal Stockholders" means each of Vincent J. Ryan, Schooner
Capital LLC, C. Richard Reese, Kent P. Dauten, B. Thomas Golisano and their
respective Affiliates.

            "Qualified Equity Offering" means an offering of Capital Stock,
other than Disqualified Stock, of the Company for Dollars, whether registered or
exempt from registration under the Securities Act.

            "Qualified Issuer" means:

            (1)   any lender party to the Credit Agreement or

            (2)   any commercial bank:

                  (i)   which has capital and surplus in excess of $500,000,000
                        and

                  (ii)  the outstanding short-term debt securities of which are
                        rated at least A-2 by Standard & Poor's Rating Group, a
                        division of McGraw-Hill, Inc. or at least P-2 by Moody's
                        Investors Service, or carry an equivalent rating by a
                        nationally recognized rating agency if both of the two
                        named rating agencies cease publishing ratings of
                        investments.

            "Qualifying Sale and Leaseback Transaction" means any Sale and
Leaseback Transaction between the Company or any of its Restricted Subsidiaries
and any bank, insurance company or other lender or investor providing for the
leasing to the Company or such Restricted Subsidiary of any


                                       14
<PAGE>

property (real or personal) which has been or is to be sold or transferred by
the Company or such Restricted Subsidiary to such lender or investor or to any
Person to whom funds have been or are to be advanced by such lender or investor
and where the property in question has been constructed or acquired after the
date of the First Supplemental Indenture.

            "Refinancing Indebtedness" means new Indebtedness incurred or given
in exchange for, or the proceeds of which are used to repay, redeem, defease,
extend, refinance, renew, replace or refund, other Indebtedness; provided,
however, that:

            (1)   the principal amount of such new Indebtedness shall not exceed
                  the principal amount of Indebtedness so repaid, redeemed,
                  defeased, extended, refinanced, renewed, replaced or refunded
                  (plus the amount of fees, premiums, consent fees, prepayment
                  penalties and expenses incurred in connection therewith);

            (2)   such Refinancing Indebtedness shall have a Weighted Average
                  Life to Maturity equal to or greater than the Weighted Average
                  Life to Maturity of the Indebtedness so repaid, redeemed,
                  defeased, extended, refinanced, renewed, replaced or refunded
                  or shall mature after the maturity date of the Notes;

            (3)   to the extent such Refinancing Indebtedness refinances
                  Indebtedness that has a final maturity date occurring after
                  the initial scheduled maturity date of the Notes, such new
                  Indebtedness shall have a final scheduled maturity not earlier
                  than the final scheduled maturity of the Indebtedness so
                  repaid, redeemed, defeased, extended, refinanced, renewed,
                  replaced or refunded and shall not permit redemption at the
                  option of the holder earlier than the earliest date of
                  redemption at the option of the holder of the Indebtedness so
                  repaid, redeemed, defeased, extended, refinanced, renewed,
                  replaced or refunded;

            (4)   to the extent such Refinancing Indebtedness refinances
                  Indebtedness subordinate to the Notes, such Refinancing
                  Indebtedness shall be subordinated in right of payment to the
                  Notes and to the extent such Refinancing Indebtedness
                  refinances Notes or Indebtedness pari passu with the Notes,
                  such Refinancing Indebtedness shall be pari passu with or
                  subordinated in right of payment to the Notes, in each case on
                  terms at least as favorable to the holders of Notes as those
                  contained in the documentation governing the Indebtedness so
                  repaid, redeemed, defeased, extended, refinanced, renewed,
                  replaced or refunded; and

            (5)   with respect to Refinancing Indebtedness incurred by a
                  Restricted Subsidiary, such Refinancing Indebtedness shall
                  rank no more senior, and shall be at least as subordinated, in
                  right of payment to the Subsidiary Guarantee of such
                  Restricted Subsidiary as the Indebtedness being extended,
                  refinanced, renewed, replaced or refunded.


                                       15
<PAGE>

            "Restricted Subsidiary" means:

            (1)   each direct or indirect Subsidiary of the Company existing on
                  the date of the First Supplemental Indenture (other than Iron
                  Mountain (Netherlands) B.V. and its subsidiaries (including
                  Iron Mountain Europe Limited), Iron Mountain Cayman Ltd. and
                  its subsidiaries, Iron Mountain Mexico, S.A. de R.L. de C.V.,
                  PLRH Inc. and Upper Providence Venture I, L.P.) and

            (2)   any other direct or indirect Subsidiary of the Company formed,
                  acquired or existing after the date of the First Supplemental
                  Indenture (including an Excluded Restricted Subsidiary),

which, in the case of (1) or (2), is not designated by the Board of Directors as
an "Unrestricted Subsidiary."

            "Sale and Leaseback Transaction" means any transaction or series of
related transactions pursuant to which a Person sells or transfers any property
or asset in connection with the leasing, or the resale against installment
payments, of such property or asset to the seller or transferor.

            "Senior Bank Debt" means all Obligations outstanding under or in
connection with the Credit Agreement (including Guarantees of such Obligations
by Subsidiaries of the Company).

            "Senior Debt" means:

            (1)   the Senior Bank Debt and

            (2)   any other Indebtedness permitted to be incurred by the Company
                  or any Restricted Subsidiary, as the case may be, under the
                  terms of the First Supplemental Indenture or the Indenture,
                  unless the instrument under which such Indebtedness is
                  incurred expressly provides that it is:

                  (i)   on a parity with or subordinated in right of payment to
                        the Notes or

                  (ii)  subordinated to Senior Debt on terms substantially
                        similar to those of the Notes.

            Notwithstanding anything to the contrary in the foregoing, Senior
Debt shall not include:

            (1)   any liability for federal, state, local or other taxes owed or
                  owing by the Company;

            (2)   any Indebtedness of the Company to any of its Subsidiaries or
                  other Affiliates;

            (3)   any trade payables; or

            (4)   any Indebtedness that is incurred in violation of the First
                  Supplemental Indenture or the Indenture, provided that such
                  Indebtedness shall be deemed not to have been incurred in
                  violation of the First Supplemental Indenture or the Indenture
                  for purposes of this clause (4) if, in the case of any
                  obligations under the Credit


                                       16
<PAGE>

                  Agreement, the holders of such obligations or their agent or
                  representative shall have received a representation from the
                  Company to the effect that the incurrence of such Indebtedness
                  does not violate the provisions of the First Supplemental
                  Indenture or the Indenture.

            "Significant Subsidiary" means any Subsidiary that would be a
"significant subsidiary" as defined in Article 1, Rule 1-02 of Regulation S-X,
promulgated pursuant to the Securities Act, as such Regulation is in effect on
the date hereof.

            "Subsidiary" means, with respect to any Person, any corporation,
association or other business entity of which more than 50% of the total voting
power of shares of Capital Stock entitled (without regard to the occurrence of
any contingency) to vote in the election of directors, managers or trustees
thereof is at the time owned or controlled, directly or indirectly, by such
Person or one or more of the other Subsidiaries of such Person or a combination
thereof.

            "Treasury Rate" means, at any time of computation, the yield to
maturity at such time (as compiled by and published in the most recent Federal
Reserve Statistical Release H.15(519), which has become publicly available at
least two business days prior to the date of the redemption notice or, if such
Statistical Release is no longer published, any publicly available source of
similar market data) of United States Treasury securities with a constant
maturity most nearly equal to the Make-Whole Average Life; provided, however,
that if the Make-Whole Average Life is not equal to the constant maturity of the
United States Treasury security for which a weekly average yield is given, the
Treasury Rate shall be obtained by linear interpolation (calculated to the
nearest one-twelfth of a year) from the weekly average yields of United States
Treasury securities for which such yields are given, except that if the
Make-Whole Average Life is less than one year, the weekly average yield on
actually traded United States Treasury securities adjusted to a constant
maturity of one year shall be used.

            "Unrestricted Subsidiary" means:

            (1)   any Subsidiary that is designated by the Board of Directors as
                  an Unrestricted Subsidiary in accordance with Section 2.6(i)
                  of the First Supplemental Indenture (Section 4.14 of the
                  Indenture) and

            (2)   any Subsidiary of an Unrestricted Subsidiary.

As of the date hereof, the following Subsidiaries of the Company have been
designated as Unrestricted Subsidiaries: Iron Mountain (Netherlands) B.V. and
its subsidiaries (including Iron Mountain Europe Limited), Iron Mountain Cayman
Ltd. and its subsidiaries, Iron Mountain Mexico, S.A. de R.L. de C.V., PLRH Inc.
and Upper Providence Venture I, L.P.

            "Voting Stock" means any class or classes of Capital Stock pursuant
to which the holders thereof have the general voting power under ordinary
circumstances to elect at least a majority of the board of directors, managers
or trustees of any Person (irrespective of whether or not, at the time, stock of
any other class or classes has, or might have, voting power by reason of the
happening of any contingency).

            "Weighted Average Life to Maturity" means, when applied to any
Indebtedness at any date, the number of years obtained by dividing:


                                       17
<PAGE>

            (1)   the sum of the products obtained by multiplying (x) the amount
                  of each then remaining installment, sinking fund, serial
                  maturity or other required payment of principal, including
                  payment at final maturity, in respect thereof, by (y) the
                  number of years (calculated to the nearest one-twelfth) that
                  will elapse between such date and the making of such payment,
                  by

            (2)   the then outstanding principal amount of such Indebtedness.

            "Wholly Owned Restricted Subsidiary" means any Restricted Subsidiary
of the Company all of the outstanding Capital Stock or other ownership interests
of which (other than directors' qualifying shares) shall at the time be owned by
the Company or by one or more Wholly Owned Restricted Subsidiaries of the
Company.

            "1996 Indenture Date" means October 1, 1996.

            "1999 Indenture Date" means April 26, 1999.

            "8 1/8% Notes" means IM Canada's 8 1/8% Senior Notes due 2008 issued
pursuant to the Indenture dated as of April 7, 1998, by and among IM Canada, as
issuer, the Company and The Bank of New York, as trustee. The 8 1/8% Notes have
been guaranteed by the Company and certain of its Subsidiaries (including,
without limitation, the Guarantors) on a senior subordinated basis.

            "8 1/4% Notes" means the Company's 8 1/4% Senior Subordinated Notes
due 2011 issued pursuant to the Indenture dated April 26, 1999, by and among the
Company, certain of its subsidiaries and The Bank of New York, as trustee.

            "8 3/4% Notes" means the Company's 8 3/4% Senior Subordinated Notes
due 2009 issued pursuant to the Indenture dated October 24, 1997, by and among
the Company, certain of its subsidiaries and The Bank of New York, as trustee.

            "9 1/8% Notes" means the Company's 9 1/8% Senior Subordinated Notes
due 2007, issued pursuant to the Indenture dated as of July 7, 1997, by and
between the Company, as issuer, and The Bank of New York, as trustee.

            "10 1/8% Notes" means the Company's 10 1/8% Senior Subordinated
Notes due 2006 issued pursuant to the Indenture dated October 1, 1996, by and
among the Company, certain of its subsidiaries and First Bank National
Association, as trustee.

            "11 1/8% Notes" means the Company's 11 1/8% Senior Subordinated
Notes due 2006 issued pursuant to the Indenture dated as of July 15, 1996,
between the Company, as issuer, and United States Trust Company of New York, as
trustee.

            (b)   Other Definitions.

            The definitions of the following terms may be found in the Sections
indicated as follows:

<TABLE>
<CAPTION>
                  Term                                        Defined in Section

                  <S>                                         <C>
                  "Affiliate Transaction"                     2.6(f)


                                       18
<PAGE>

                  "Asset Sale"                                2.6(k)
                  "Asset Sale Offer"                          2.6(k)
                  "Bankruptcy Law"                            2.8
                  "Change of Control Offer"                   2.6(l)
                  "Change of Control Payment"                 2.6(l)
                  "Change of Control Payment Date"            2.6(l)
                  "Commencement Date"                         2.6(k)
                  "Custodian"                                 2.8
                  "DTC"                                       2.3
                  "Event of Default"                          6.1
                  "Excess Proceeds"                           2.6(k)
                  "First Supplemental Indenture"              Preamble
                  "incur"                                     2.6(c)
                  "Indenture"                                 Preamble
                  "Restricted Payments"                       2.6(b)
</TABLE>

                                   ARTICLE 2.

                           FORM AND TERMS OF THE NOTES

Section 2.1. Form and Dating.(a) General. The Notes and the Trustee's
certificate of authentication shall be substantially in the form of Exhibit A
attached hereto. The Notes may have notations, legends or endorsements required
by law, stock exchange rule or usage. Each Note shall be dated the date of its
authentication. The Notes shall be in denominations of $1,000 and integral
multiples thereof.

            The terms and provisions contained in the Notes shall constitute,
and are hereby expressly made, a part of the First Supplemental Indenture and
the Indenture and the Company, the Guarantors and the Trustee, by their
execution and delivery of the First Supplemental Indenture and the Indenture (or
in the case of any Guarantor that becomes such after the date hereof, a
supplemental indenture pursuant to Section 2.6(h) of this First Supplemental
Indenture (Section 4.13 of the Indenture)), expressly agree to such terms and
provisions and to be bound thereby.

            (b) Global Notes. Notes shall be issued initially in the form of the
Global Notes, which shall be deposited on behalf of the purchasers of the Notes
represented thereby with the Depository at its New York office, and registered
in the name of the Depository or a nominee of the Depository, duly executed by
the Company and authenticated by the Trustee as hereinafter provided. The
aggregate principal amount of the Global Notes may from time to time be
increased or decreased by adjustments made on the records of the Trustee and the
Depository or its nominee as hereinafter provided.

            The Global Notes shall represent such of the outstanding Notes as
shall be specified therein and shall provide that it shall represent the
aggregate amount of outstanding Notes from time to time endorsed thereon and
that the aggregate amount of outstanding Notes represented thereby may from time
to time be reduced or increased, as appropriate, to reflect exchanges and
redemptions. Any endorsement of the Global Notes to reflect the amount of any
increase or decrease in the amount of outstanding Notes represented thereby
shall be made by the Trustee or the Service Agent, at the direction of the
Trustee, in accordance with instructions given by the Holder thereof as required
by Section 2.4 of this First Supplemental Indenture.


                                       19
<PAGE>

            Except as set forth in Section 2.4 of this First Supplemental
Indenture, the Global Notes may be transferred, in whole and not in part, only
to another nominee of the Depository or to a successor of the Depository or its
nominee.

            (c) Book-Entry Provisions. This Section 2.1(c) shall apply only to
the Global Notes deposited with or on behalf of the Depository.

            The Company shall execute and the Trustee shall, in accordance with
this Section 2.1(c), authenticate and deliver the Global Notes that (i) shall be
registered in the name of the Depository or the nominee of the Depository and
(ii) shall be delivered by the Trustee to the Depository or pursuant to the
Depository's instructions or held by the Service Agent.

            Agent Members shall have no rights either under the First
Supplemental Indenture or the Indenture with respect to any Global Notes held on
their behalf by the Depository or by the Service Agent or under such Global
Notes, and the Depository may be treated by the Company, the Trustee and any
agent of the Company or the Trustee as the absolute owner of such Global Notes
for all purposes whatsoever.

            (d) Definitive Notes. Notes issued in certificated form shall be
substantially in the form of Exhibit A attached hereto (but without including
the text referred to in Section 2.15.3 of the Indenture). Except as provided in
Section 2.4, owners of beneficial interests in the Global Notes will not be
entitled to receive physical delivery of certificated Securities.

Section 2.2. Execution and Authentication.

            The Trustee shall, upon a written order of the Company signed by an
Officer, authenticate up to $225,000,000 aggregate principal amount of Initial
Notes and up to $275,000,000 of Additional Notes.

Section 2.3. Depository and Paying Agent for Notes.

            The Company initially appoints The Depository Trust Company ("DTC")
to act as Depository with respect to the Global Notes. The Company initially
appoints the Trustee to act as the Registrar, Paying Agent and Service Agent
with respect to the Global Notes.

Section 2.4. Transfer and Exchange of Notes.

            (a) Transfer and Exchange of Beneficial Interests in Global Notes.
The transfer and exchange of beneficial interests in the Global Notes shall be
effected through the Depository, in accordance with the First Supplemental
Indenture and the Indenture and the procedures of the Depository therefor.
Beneficial interests in the Global Notes may be transferred to Persons who take
delivery thereof in the form of a beneficial interest in the Global Notes.

            (b) Transfer and Exchange of Definitive Notes. When Definitive Notes
are presented by a Holder to the Registrar with a request:

                  (x)   to register the transfer of the Definitive Notes; or


                                       20
<PAGE>

                  (y)   to exchange such Definitive Notes for an equal principal
                        amount of Definitive Notes of other authorized
                        denominations,

the Registrar shall register the transfer or make the exchange as requested if
its requirements for such transactions are met; provided, however, that the
Definitive Notes presented or surrendered for register of transfer or exchange
shall be duly endorsed or accompanied by a written instruction of transfer in
form satisfactory to the Registrar duly executed by such Holder or by his
attorney, duly authorized in writing.

            (c) Restrictions on Transfer and Exchange of Global Notes.
Notwithstanding any other provision of the First Supplemental Indenture or the
Indenture (other than the provisions set forth in subsection (d) of this Section
2.4), the Global Notes may not be transferred as a whole except by the
Depository to a nominee of the Depository or by a nominee of the Depository to
the Depository or another nominee of the Depository or by the Depository or any
such nominee to a successor Depository or a nominee of such successor
Depository.

            (d) Authentication of Definitive Notes in Absence of Depository. If
at any time:

                  (i)   the Depository for the Notes notifies the Company that
                        the Depository is unwilling or unable to continue as
                        Depository for the Global Notes and a successor
                        Depository for the Global Notes is not appointed by the
                        Company within 90 days after delivery of such notice; or

                  (ii)  the Company at its sole discretion, notifies the Trustee
                        in writing that it elects to cause the issuance of
                        Definitive Notes under the First Supplemental Indenture
                        and the Indenture,

then the Company shall execute, and the Trustee shall, upon receipt of an
authentication order in accordance with Section 2.2 hereof, authenticate and
deliver, Definitive Notes in an aggregate principal amount equal to the
principal amount of the Global Notes in exchange for such Global Notes.

            (e) Cancellation and/or Adjustment of the Global Notes. At such time
as all beneficial interests in the Global Notes have been exchanged for
Definitive Notes, redeemed, repurchased or canceled, the Global Notes shall be
returned to or retained and canceled by the Trustee in accordance with Section
2.12 of the Indenture. At any time prior to such cancellation, if any beneficial
interest in the Global Notes is exchanged for Definitive Notes, redeemed,
repurchased or canceled, the aggregate principal amount of Notes represented by
the Global Notes shall be reduced accordingly and an endorsement shall be made
on the Global Notes, by the Trustee or the Service Agent, at the direction of
the Trustee, to reflect such reduction. A Definitive Note may be exchanged for a
beneficial interest in the Global Note only upon receipt by the Trustee of a
Definitive Note, duly endorsed or accompanied by appropriate instruments of
transfer, in form satisfactory to the Trustee, together with written
instructions directing the Trustee to make an endorsement on the Global Note to
reflect an increase in the aggregate principal amount of the Notes represented
by the Global Note; in which case the Trustee shall cancel such Definitive Note
and cause the aggregate principal amount of Notes represented by the Global Note
to be increased accordingly. If no Global Note is then outstanding, the Company
shall issue and the Trustee shall authenticate a new Global Note in the
appropriate principal amount.

            (f) General Provisions Relating to Transfers and Exchanges.


                                       21
<PAGE>

                  (i)   To permit registrations of transfers and exchanges, the
                        Company shall execute and the Trustee shall authenticate
                        Definitive Notes and the Global Notes at the Registrar's
                        request.

                  (ii)  No service charge shall be made to a Holder for any
                        registration of transfer or exchange, but the Company
                        may require payment of a sum sufficient to cover any
                        transfer tax or similar governmental charge payable in
                        connection therewith (other than any such transfer taxes
                        or similar governmental charge payable upon exchange or
                        transfer pursuant to Section 2.4 of this First
                        Supplemental Indenture).

                  (iii) All Definitive Notes and the Global Notes issued upon
                        any registration of transfer or exchange of Definitive
                        Notes or the Global Notes shall be the valid obligations
                        of the Company, evidencing the same debt, and entitled
                        to the same benefits under the First Supplemental
                        Indenture and the Indenture, as the Definitive Notes or
                        the Global Notes surrendered upon such registration of
                        transfer or exchange.

                  (iv)  Prior to due presentment for the registration of a
                        transfer of any Note, the Trustee, any Agent, the
                        Company and any Guarantor may deem and treat the Person
                        in whose name any Note is registered as the absolute
                        owner of such Note for all purposes, including receiving
                        payment of principal of and interest on such Notes, and
                        neither the Trustee, any Agent, the Company nor any
                        Guarantor shall be affected by notice to the contrary.

                  (v)   The Trustee shall authenticate Definitive Notes and the
                        Global Notes in accordance with the provisions of
                        Section 2.2 of the First Supplemental Indenture and
                        Section 2.3 of the Indenture.

Section 2.5. Redemption.

            With respect to the Notes issued under this First Supplemental
Indenture, the following Sections supplement Article III of the Indenture:

            Section 3.7. Optional Redemption.

            Prior to April 1, 2006, the Notes shall be subject to redemption at
any time at the option of the Company, in whole or in part, upon not less than
30 nor more than 60 days' notice, at the Make-Whole Price, plus accrued and
unpaid interest, to but excluding the applicable redemption date. On and after
April 1, 2006, the Notes will be subject to redemption at any time at the option
of the Company, in whole or in part, upon not less than 30 nor more than 60
days' notice, at the redemption prices (expressed as percentages of principal
amount) set forth below, plus accrued and unpaid interest, to but excluding the
applicable redemption date, if redeemed during the twelve-month period beginning
on April 1 of the years indicated below:

<TABLE>
<CAPTION>
             Year                                                     Percentage
             ----                                                     ----------

             <S>                                                      <C>
             2006................................................       104.313%


                                       22
<PAGE>

             2007................................................       102.875%
             2008................................................       101.438%
             2009 and thereafter.................................       100.000%
</TABLE>

            Notwithstanding the foregoing, at any time prior to April 1, 2004,
the Company may redeem up to 35% of the initial principal amount of the Notes
originally issued with the net proceeds of one or more Qualified Equity
Offerings at a redemption price equal to 108.625% of the principal amount of
such Notes, plus accrued and unpaid interest to but excluding the redemption
date; provided, that at least 65% of the principal amount of Notes originally
issued remains outstanding immediately after the occurrence of any such
redemption and that such redemption occurs within 60 days following the closing
of any such Qualified Equity Offering.

            Section 3.8. Mandatory Redemption.

            The Company shall not be required to make mandatory redemption
payments or sinking fund payments with respect to the Notes.

            Section 3.9. Asset Sale Offers.

            In the event that the Company shall commence an Asset Sale Offer
pursuant to Section 4.16 hereof, it shall follow the procedures specified below:

            The Asset Sale Offer shall remain open for 20 Business Days after
the Commencement Date relating to such Asset Sale Offer, except to the extent
required to be extended by applicable law (as so extended, the "Offer Period").
No later than one Business Day after the termination of the Offer Period (the
"Purchase Date"), the Company shall purchase the principal amount (the "Offer
Amount") of Notes required to be purchased in such Asset Sale Offer pursuant to
Sections 3.2 and 4.16 hereof or, if less than the Offer Amount has been
tendered, all Notes tendered in response to the Asset Sale Offer.

            If the Purchase Date is on or after an interest payment record date
and on or before the related interest payment date, any interest accrued to such
Purchase Date shall be paid to the Person in whose name a Note is registered at
the close of business on such record date, and no additional interest shall be
payable to Holders who tender Notes pursuant to the Asset Sale Offer.

            On the Commencement Date of any Asset Sale Offer, the Company shall
send or cause to be sent, by first class mail, a notice to each of the Holders,
with a copy to the Trustee. Such notice, which shall govern the terms of the
Asset Sale Offer, shall contain all instructions and materials necessary to
enable the Holders to tender Notes pursuant to the Asset Sale Offer and shall
state:

            (1)   that the Asset Sale Offer is being made pursuant to this
                  Section 3.9 and Section 4.16 hereof and the length of time the
                  Asset Sale Offer shall remain open;

            (2)   the Offer Amount, the purchase price and the Purchase Date;

            (3)   that any Note not tendered or accepted for payment shall
                  continue to accrue interest;


                                       23
<PAGE>

            (4)   that, unless the Company defaults in the payment of the
                  purchase price, any Note accepted for payment pursuant to the
                  Asset Sale Offer shall cease to accrue interest after the
                  Purchase Date;

            (5)   that Holders electing to have a Note purchased pursuant to any
                  Asset Sale Offer shall be required to surrender the Note, with
                  the form entitled "Option of Holder to Elect Purchase" on the
                  reverse of the Note completed, to the Company, a depositary,
                  if appointed by the Company, or a Paying Agent at the address
                  specified in the notice prior to the close of business on the
                  Business Day preceding the Purchase Date;

            (6)   that Holders shall be entitled to withdraw their election if
                  the Company, depositary or Paying Agent, as the case may be,
                  receives, not later than the close of business on the Business
                  Day preceding the termination of the Offer Period, a facsimile
                  transmission or letter setting forth the name of the Holder,
                  the principal amount of the Note the Holder delivered for
                  purchase and a statement that such Holder is withdrawing such
                  Holder's election to have the Note purchased;

            (7)   that, if the aggregate principal amount of Notes surrendered
                  by Holders exceeds the Offer Amount, the Trustee shall select
                  the Notes to be purchased on a pro rata basis (with such
                  adjustments as may be deemed appropriate by the Company so
                  that only Notes in denominations of $1,000, or integral
                  multiples thereof, shall be purchased); and

            (8)   that Holders whose Notes were purchased only in part shall be
                  issued new Notes equal in principal amount to the unpurchased
                  portion of the Notes surrendered.

            On or before 12:00 noon on each Purchase Date, the Company shall
irrevocably deposit with the Trustee or Paying Agent in immediately available
funds the aggregate purchase price with respect to a principal amount of Notes
equal to the Offer Amount, together with accrued interest thereon, to be held
for payment in accordance with the terms of this Section 3.9. On the Purchase
Date, the Company shall, to the extent lawful, (i) accept for payment, on a pro
rata basis to the extent necessary, an aggregate principal amount equal to the
Offer Amount of Notes and other notes (in accordance with the terms of Section
4.16 of the Indenture) tendered pursuant to the Asset Sale Offer, or if less
than the Offer Amount has been tendered, all Notes and such other notes or
portions thereof tendered, (ii) deliver or cause the Paying Agent or depositary,
as the case may be, to deliver to the Trustee Notes so accepted and (iii)
deliver to the Trustee an Officers' Certificate stating that such Notes or
portions thereof were accepted for payment by the Company in accordance with the
terms of this Section 3.9. The Company, depositary or Paying Agent, as the case
may be, shall promptly (but in any case not later than three Business Days after
the Purchase Date) mail or deliver to each tendering Holder an amount equal to
the purchase price with respect to the Notes tendered by such Holder and
accepted by the Company for purchase, and the Company shall promptly issue a new
Note, and the Trustee shall authenticate and mail or deliver such new Note, to
such Holder, equal in principal amount to any unpurchased portion of such
Holder's Notes surrendered. Any Note not accepted in the Asset Sale Offer shall
be promptly mailed or delivered by the Company to the Holder thereof. The
Company shall publicly announce in a newspaper of general circulation the
results of the Asset Sale Offer on the Purchase Date.


                                       24
<PAGE>

            The Asset Sale Offer shall be made by the Company in compliance with
all applicable laws, including, without limitation, Regulation 14E of the
Exchange Act and the rules thereunder, to the extent applicable, and all other
applicable federal and state securities laws.

            Each purchase pursuant to this Section 3.9 shall be made pursuant to
the provisions of the second paragraph of Section 3.5 hereof to the extent
applicable.

            In the event the amount of Excess Proceeds to be applied to an Asset
Sale Offer would result in the purchase of a principal amount of Notes which is
not evenly divisible by $1,000, the Trustee shall promptly refund to the Company
the portion of such Excess Proceeds that is not necessary to purchase the
immediately lesser principal amount of Notes that is so divisible.

Section 2.6. Covenants.

            With respect to the Notes issued under this First Supplemental
Indenture, Section (a) below replaces Section 4.2 of the Indenture, Section (m)
below replaces Section 4.5 of the Indenture and each other Section is added to
Article IV of the Indenture.

            (a) Reports.

            Section 4.2. Reports. Whether or not required by the rules and
regulations of the SEC, so long as any Notes are outstanding, the Company
will furnish to the Holders of Notes:

            (1)   all quarterly and annual financial information that would be
                  required to be contained in a filing with the SEC on Forms
                  10-Q and 10-K if the Company were required to file such Forms,
                  including a "Management's Discussion and Analysis of Financial
                  Condition and Results of Operations" and, with respect to the
                  annual information only, a report thereon by the Company's
                  certified independent accountants and

            (2)   all financial information that would be required to be
                  included in a Form 8-K filed with the SEC if the Company were
                  required to file such reports.

In addition, whether or not required by the rules and regulations of the SEC,
the Company will file a copy of all such information and reports with the SEC
for public availability (unless the SEC will not accept such a filing) and make
such information available to investors who request it in writing.

            (b) Restricted Payments.

            Section 4.7. Restricted Payments. The Company shall not, and
shall not permit any of its Restricted Subsidiaries to, directly or
indirectly:

            (1)   declare or pay any dividend or make any distribution on
                  account of the Company's or any of its Restricted
                  Subsidiaries' Equity Interests (other than dividends or
                  distributions payable in Equity Interests (other than
                  Disqualified Stock) of the Company or such Restricted
                  Subsidiary or dividends or distributions payable to the
                  Company or any Restricted Subsidiary);


                                       25
<PAGE>

            (2)   purchase, redeem or otherwise acquire or retire for value any
                  Equity Interests of the Company or any Restricted Subsidiary
                  or other Affiliate of the Company (other than any such Equity
                  Interests owned by the Company or any Restricted Subsidiary);

            (3)   purchase, redeem or otherwise acquire or retire prior to
                  scheduled maturity for value any Indebtedness that is
                  subordinated in right of payment to the Notes; or

            (4)   make any Investment other than a Permitted Investment (all
                  such payments and other actions set forth in clauses (1)
                  through (4) above being collectively referred to as
                  "Restricted Payments");

unless, at the time of such Restricted Payment:

                  (i)   no Default or Event of Default shall have occurred and
                        be continuing or would occur as a consequence thereof;
                        and

                  (ii)  the Company would, at the time of such Restricted
                        Payment and after giving pro forma effect thereto, have
                        been permitted to incur at least $1.00 of additional
                        Indebtedness pursuant to the test set forth in the first
                        paragraph of Section 4.8 of the Indenture; and

                  (iii) such Restricted Payment, together with the aggregate of
                        all other Restricted Payments made by the Company and
                        its Restricted Subsidiaries after the 1996 Indenture
                        Date is less than (x) the cumulative EBITDA of the
                        Company, minus 1.75 times the cumulative Consolidated
                        Interest Expense of the Company, in each case for the
                        period (taken as one accounting period) from June 30,
                        1996, to the end of the Company's most recently ended
                        fiscal quarter for which internal financial statements
                        are available at the time of such Restricted Payment,
                        plus (y) the aggregate net Equity Proceeds received by
                        the Company from the issuance or sale since the 1996
                        Indenture Date of Equity Interests of the Company or of
                        debt securities of the Company that have been converted
                        into such Equity Interests (other than Equity Interests
                        or convertible debt securities sold to a Restricted
                        Subsidiary of the Company and other than Disqualified
                        Stock or debt securities that have been converted into
                        Disqualified Stock), plus (z) $2.0 million.

            The foregoing provisions will not prohibit:

            (1)   the payment of any dividend within 60 days after the date of
                  declaration thereof, if at said date of declaration such
                  payment would have complied with the provisions of the
                  Indenture;

            (2)   the redemption, repurchase, retirement or other acquisition or
                  retirement for value of any Equity Interests of the Company in
                  exchange for, or with the net cash proceeds of, the
                  substantially concurrent sale (other than to a Restricted


                                       26
<PAGE>

                  Subsidiary of the Company) of other Equity Interests of the
                  Company (other than any Disqualified Stock);

            (3)   the defeasance, redemption, repurchase, retirement or other
                  acquisition or retirement for value of Indebtedness that is
                  subordinated in right of payment to the Notes in exchange for,
                  or with the net cash proceeds of, a substantially concurrent
                  issuance and sale (other than to a Restricted Subsidiary of
                  the Company) of Equity Interests of the Company (other than
                  Disqualified Stock);

            (4)   the defeasance, redemption, repurchase, retirement or other
                  acquisition or retirement for value of Indebtedness that is
                  subordinated in right of payment to the Notes in exchange for,
                  or with the net cash proceeds of, a substantially concurrent
                  issue and sale (other than to the Company or any of its
                  Restricted Subsidiaries) of Refinancing Indebtedness;

            (5)   the repurchase of any Indebtedness subordinated in right of
                  payment to the Notes at a purchase price not greater than 101%
                  of the principal amount of such Indebtedness in the event of a
                  Change of Control in accordance with provisions similar to the
                  covenant set forth in Section 2.6(l) of the First Supplemental
                  Indenture (Section 4.17 of the Indenture), provided that prior
                  to or contemporaneously with such repurchase the Company has
                  made the Change of Control Offer as provided in such covenant
                  with respect to the Notes and has repurchased all Notes
                  validly tendered for payment in connection with such Change of
                  Control Offer; and

            (6)   additional payments to current or former employees or
                  directors of the Company for repurchases of stock, stock
                  options or other equity interests, provided that the aggregate
                  amount of all such payments under this clause (6) does not
                  exceed $0.5 million in any year and $2.0 million in the
                  aggregate.

            The Restricted Payments described in clauses (2), (3), (5) and (6)
of the immediately preceding paragraph will be Restricted Payments that shall be
permitted to be taken in accordance with such paragraph but shall reduce the
amount that would otherwise be available for Restricted Payments under clause
(iii) of the first paragraph of this Section, and the Restricted Payments
described in clauses (1) and (4) of the immediately preceding paragraph shall be
Restricted Payments that shall be permitted to be taken in accordance with such
paragraph and shall not reduce the amount that would otherwise be available for
Restricted Payments under clause (iii) of the first paragraph of this Section.

            If an Investment results in the making of a Restricted Payment, the
aggregate amount of all Restricted Payments deemed to have been made as
calculated under the foregoing provision shall be reduced by the amount of any
net reduction in such Investment (resulting from the payment of interest or
dividends, loan repayment, transfer of assets or otherwise) to the extent such
net reduction is not included in the Company's EBITDA; provided, however, that
the total amount by which the aggregate amount of all Restricted Payments may be
reduced may not exceed the lesser of (a) the cash proceeds received by the
Company and its Restricted Subsidiaries in connection with such net reduction
and (b) the initial amount of such Investment.


                                       27
<PAGE>

            If the aggregate amount of all Restricted Payments calculated under
the foregoing provision includes an Investment in an Unrestricted Subsidiary or
other Person that thereafter becomes a Restricted Subsidiary, such Investment
will no longer be counted as a Restricted Payment for purposes of calculating
the aggregate amount of Restricted Payments. For the purpose of making any
calculations under the Indenture:

            (1)   an Investment will include the fair market value of the net
                  assets of any Restricted Subsidiary at the time that such
                  Restricted Subsidiary is designated an Unrestricted Subsidiary
                  and will exclude the fair market value of the net assets of
                  any Unrestricted Subsidiary that is designated as a Restricted
                  Subsidiary;

            (2)   any property transferred to or from an Unrestricted Subsidiary
                  will be valued at fair market value at the time of such
                  transfer, provided that, in each case, the fair market value
                  of an asset or property is as determined by the Board of
                  Directors in good faith and

            (3)   subject to the foregoing, the amount of any Restricted
                  Payment, if other than cash, will be determined by the Board
                  of Directors, whose good faith determination will be
                  conclusive.

            The Board of Directors may designate a Restricted Subsidiary to be
an Unrestricted Subsidiary in compliance with the Section 4.14 of the Indenture.
Upon such designation, all outstanding Investments by the Company and its
Restricted Subsidiaries (except to the extent repaid in cash) in the Subsidiary
so designated will be deemed to be Restricted Payments made at the time of such
designation and will reduce the amount available for Restricted Payments under
the first paragraph of this covenant. Such designation will only be permitted if
such Restricted Payment would be permitted at such time and if such Restricted
Subsidiary otherwise meets the definition of an Unrestricted Subsidiary.

            (c) Incurrence of Indebtedness and Issuance of Preferred Stock.

            Section 4.8. Incurrence of Indebtedness and Issuance of Preferred
Stock. The Company shall not, and shall not permit any of its Restricted
Subsidiaries to, directly or indirectly, create, incur, issue, assume,
guaranty or otherwise become directly or indirectly liable with respect to
(collectively, "incur") any Indebtedness (including Acquired Debt) and the
Company shall not permit any of its Restricted Subsidiaries to issue any
shares of preferred stock; provided, however, that the Company may incur
Indebtedness and may permit a Restricted Subsidiary to incur Indebtedness if
at the time of such incurrence and after giving effect thereto the Leverage
Ratio would be less than 6.5 to 1.0.

            The foregoing limitations shall not apply to:

            (1)   the incurrence by the Company or any Restricted Subsidiary of
                  Senior Bank Debt in an aggregate amount not to exceed $100.0
                  million at any one time outstanding;

            (2)   the issuance by the Restricted Subsidiaries of Subsidiary
                  Guarantees;

            (3)   the incurrence by the Company and its Restricted Subsidiaries
                  of the Existing Indebtedness;


                                       28
<PAGE>

            (4)   the issuance by the Company of the Notes;

            (5)   the incurrence by the Company and its Restricted Subsidiaries
                  of Capital Lease Obligations and/or additional Indebtedness
                  constituting purchase money obligations up to an aggregate of
                  $5.0 million at any one time outstanding, provided that the
                  Liens securing such Indebtedness constitute Permitted Liens;

            (6)   the incurrence of Indebtedness between (i) the Company and its
                  Restricted Subsidiaries and (ii) the Restricted Subsidiaries;

            (7)   Hedging Obligations that are incurred for the purpose of
                  fixing or hedging interest rate risk with respect to any
                  floating rate Indebtedness that is permitted by the terms of
                  the Indenture to be outstanding;

            (8)   the incurrence by the Company and its Restricted Subsidiaries
                  of Indebtedness arising out of letters of credit, performance
                  bonds, surety bonds and bankers' acceptances incurred in the
                  ordinary course of business up to an aggregate of $5.0 million
                  at any one time outstanding;

            (9)   the incurrence by the Company and its Restricted Subsidiaries
                  of Indebtedness consisting of guarantees, indemnities or
                  obligations in respect of purchase price adjustments in
                  connection with the acquisition or disposition of assets,
                  including, without limitation, shares of Capital Stock; and

            (10)  the incurrence by the Company and its Restricted Subsidiaries
                  of Refinancing Indebtedness issued in exchange for, or the
                  proceeds of which are used to repay, redeem, defease, extend,
                  refinance, renew, replace or refund, Indebtedness referred to
                  in clauses (2) through (5) above, and this clause (10) or that
                  was otherwise permitted to be incurred pursuant to the test
                  set forth in the first paragraph of this Section 4.8.

            (d) Liens.

            Section 4.9. Liens. Neither the Company nor any of its Restricted
Subsidiaries may directly or indirectly create, incur, assume or suffer to
exist any Lien (other than a Permitted Lien) upon any property or assets now
owned or hereafter acquired, or any income, profits or proceeds therefrom, or
assign or otherwise convey any right to receive income therefrom, unless (a)
in the case of any Lien securing any Indebtedness that is subordinate to the
Notes, the Notes are secured by a Lien on such property, assets or proceeds
that is senior in priority to such Lien and (b) in the case of any other
Lien, the Notes are equally and ratably secured with the obligation or
liability secured by such Lien.

            (e) Dividend and Other Payment Restrictions Affecting Restricted
Subsidiaries.

            Section 4.10. Dividend and Other Payment Restrictions Affecting
Restricted Subsidiaries. The Company shall not, and shall not permit any of
its Restricted Subsidiaries to, directly or indirectly, create or otherwise
cause or suffer to exist or become effective any encumbrance or restriction
on the ability of any Restricted Subsidiary to:

                                       29
<PAGE>

            (1)   (i) pay dividends or make any other distributions to the
                  Company or any of its Restricted Subsidiaries (A) on its
                  Capital Stock or (B) with respect to any other interest or
                  participation in, or measured by, its profits, or (ii) pay any
                  Indebtedness owed to the Company or any of its Restricted
                  Subsidiaries;

            (2)   make loans or advances to the Company or any of its Restricted
                  Subsidiaries; or

            (3)   transfer any of its properties or assets to the Company or any
                  of its Restricted Subsidiaries.

            However, the preceding restrictions will not apply to encumbrances
or restrictions existing under or by reason of:

            (1)   Existing Indebtedness;

            (2)   the Credit Agreement as in effect as of the date of the
                  Indenture, and any amendments, modifications, restatements,
                  renewals, increases, supplements, refundings, replacements or
                  refinancing thereof, provided that such amendments,
                  modifications, restatements, renewals, increases, supplements,
                  refundings, replacements or refinancings are no more
                  restrictive in the aggregate with respect to such dividend and
                  other payment restrictions than those contained in the Credit
                  Agreement as in effect on the date of the Indenture;

            (3)   the Indenture and the Notes;

            (4)   applicable law;

            (5)   any instrument governing Indebtedness or Capital Stock of a
                  Person acquired by the Company or any of its Restricted
                  Subsidiaries as in effect at the time of such acquisition
                  (except to the extent such Indebtedness was incurred in
                  connection with or in contemplation of such acquisition),
                  which encumbrance or restriction is not applicable to any
                  Person, or the properties or assets of any Person, other than
                  the Person, or the property or assets of the Person, so
                  acquired, provided that the EBITDA of such Person is not taken
                  into account in determining whether such acquisition was
                  permitted by the terms of the Indenture;

            (6)   customary non-assignment provisions in leases entered into in
                  the ordinary course of business and consistent with past
                  practices;

            (7)   restrictions on the transfer of property subject to purchase
                  money obligations or Capital Lease Obligations otherwise
                  permitted by clause (5) of Section 4.8 of the Indenture;

            (8)   permitted Refinancing Indebtedness, provided that the
                  restrictions contained in the agreements governing such
                  Refinancing Indebtedness are no more restrictive in the
                  aggregate than those contained in the agreements governing the
                  Indebtedness being refinanced; or


                                       30
<PAGE>

            (9)   any agreement or instrument governing Indebtedness of an
                  Excluded Restricted Subsidiary provided that (i) at the time
                  such agreement or instrument is entered into, such Excluded
                  Restricted Subsidiary and its Restricted Subsidiaries have a
                  Leverage Ratio of less than 6.5 to 1.0 and (ii) neither such
                  Excluded Restricted Subsidiary nor any of its Restricted
                  Subsidiaries shall, directly or indirectly, incur any
                  Indebtedness (including Acquired Debt) unless at the time of
                  such incurrence and after giving effect thereto, the Leverage
                  Ratio for such Excluded Restricted Subsidiary and its
                  Restricted Subsidiaries would be less than 6.5 to 1.0. For
                  purposes of determining the Leverage Ratio under this clause
                  (9) only, all references to the "Company" and its "Restricted
                  Subsidiaries" or similar references in the definition of
                  "Leverage Ratio" and other defined terms necessary to
                  determine the Leverage Ratio shall be deemed to refer to such
                  Excluded Restricted Subsidiary and its Restricted
                  Subsidiaries, respectively.

            (f) Transactions with Affiliates.

                Section 4.11. Transactions with Affiliates. The Company shall
not, and shall not permit any of its Restricted Subsidiaries to, sell, lease,
transfer or otherwise dispose of any of its properties or assets to, or
purchase any property or assets from, or enter into any contract, agreement,
understanding, loan, advance or guarantee with, or for the benefit of, any
Affiliate (each of the foregoing, an "Affiliate Transaction"), unless:

            (a)   such Affiliate Transaction is on terms that are no less
                  favorable to the Company or the relevant Restricted Subsidiary
                  than those that would have been obtained in a comparable
                  transaction by the Company or such Restricted Subsidiary with
                  a non-Affiliated Person and

            (b)   the Company delivers to the Trustee:

                  (i)   with respect to any Affiliate Transaction involving
                        aggregate payments in excess of $5.0 million, a
                        resolution of the Board of Directors set forth in an
                        Officers' Certificate certifying that such Affiliate
                        Transaction complies with clause (a) above and such
                        Affiliate Transaction is approved by a majority of the
                        disinterested members of the Board of Directors and

                  (ii)  with respect to any Affiliate Transaction involving
                        aggregate payments in excess of $10.0 million, an
                        opinion as to the fairness to the Company or such
                        Restricted Subsidiary from a financial point of view
                        issued by an investment banking firm of national
                        standing.

            The following items shall not be deemed Affiliate Transactions and
therefore, will not be subject to the provisions of the prior paragraph:

            (1)   any employment agreement entered into by the Company or any of
                  its Restricted Subsidiaries in the ordinary course of business
                  and consistent with the past practice of the Company or such
                  Restricted Subsidiary;


                                       31
<PAGE>

            (2)   transactions between or among the Company and/or its
                  Restricted Subsidiaries;

            (3)   transactions permitted by the provisions of Section 4.7 of the
                  Indenture; and

            (4)   the grant of stock, stock options or other equity interests to
                  employees and directors of the Company and any Restricted
                  Subsidiary in accordance with duly adopted Company stock
                  grant, stock option and similar plans.

            The provisions set forth in clause (b) above shall not apply to
sales of inventory by the Company or any Restricted Subsidiary to any Affiliate
in the ordinary course of business. The provisions of clause (b) (ii) above
shall not apply to loans or advances to the Company or any Restricted Subsidiary
from, or equity investments in the Company or any Restricted Subsidiary by, any
Affiliate to the extent permitted by the provisions of Section 4.8 of the
Indenture.

            (g) Certain Senior Subordinated Debt.

            Section 4.12. Certain Senior Subordinated Debt. The Company shall
not incur any Indebtedness that is subordinated or junior in right of payment
to any Senior Debt of the Company and senior in any respect in right of
payment to the Notes. The Company shall not permit any Restricted Subsidiary
to incur any Indebtedness that is subordinated or junior in right of payment
to its Senior Debt and senior in any respect in right of payment to its
Subsidiary Guarantee.

            (h) Additional Subsidiary Guarantees.

            Section 4.13. Additional Subsidiary Guarantees. If any entity
(other than an Excluded Restricted Subsidiary) shall become a Restricted
Subsidiary after the date of the First Supplemental Indenture, then such
Restricted Subsidiary shall execute a supplemental indenture in the form of
Exhibit B attached hereto, pursuant to which it shall provide a Subsidiary
Guarantee, and deliver an Opinion of Counsel with respect thereto, in
accordance with the terms of the Indenture.

            No Restricted Subsidiary (including any Excluded Restricted
Subsidiary) shall consolidate with or merge with or into (whether or not such
Restricted Subsidiary is the surviving Person), another Person (other than the
Company) whether or not affiliated with such Restricted Subsidiary unless:

            (1)   subject to the provisions of the immediately following
                  sentence, the Person formed by or surviving any such
                  consolidation or merger (if other than such Restricted
                  Subsidiary) assumes all the obligations of such Restricted
                  Subsidiary under its Subsidiary Guarantee (except in the case
                  of an Excluded Restricted Subsidiary) pursuant to a
                  supplemental indenture in form and substance reasonably
                  satisfactory to the Trustee;

            (2)   immediately after giving effect to such transaction, no
                  Default or Event of Default exists; and

            (3)   such Restricted Subsidiary, or any Person formed by or
                  surviving any such consolidation or merger, would be permitted
                  to incur, immediately after giving


                                       32
<PAGE>

                  effect to such transaction, at least $1.00 of additional
                  Indebtedness pursuant to the test set forth in the first
                  paragraph of Section 4.8 of the Indenture.

In the event of:

            (1)   a sale or other disposition of all of the assets of any
                  Restricted Subsidiary, by way of merger, consolidation or
                  otherwise;

            (2)   a sale or other disposition of all of the capital stock of any
                  Restricted Subsidiary; or

            (3)   the designation of a Restricted Subsidiary as an Unrestricted
                  Subsidiary in accordance with the terms of Section 4.14 of the
                  Indenture,

then such Subsidiary (in the event of a sale or other disposition, by way of
such a merger, consolidation or otherwise, of all of the capital stock of such
Restricted Subsidiary or in the event of the designation of such Restricted
Subsidiary as an Unrestricted Subsidiary) or the Person acquiring the property
(in the event of a sale or other disposition of all of the assets of such
Restricted Subsidiary) will be released and relieved of any obligations under
its Subsidiary Guarantee, provided that the Net Proceeds of such sale or other
disposition are applied in accordance with the applicable provisions of Section
4.16 of the Indenture.

            (i) Designation of Unrestricted Subsidiaries.

            Section 4.14. Designation of Unrestricted Subsidiaries. The Board
of Directors may designate any Subsidiary (including any Restricted
Subsidiary or any newly acquired or newly formed Subsidiary) to be an
Unrestricted Subsidiary so long as:

            (1)   neither the Company nor any Restricted Subsidiary is directly
                  or indirectly liable for any Indebtedness of such Subsidiary;

            (2)   no default with respect to any Indebtedness of such Subsidiary
                  would permit (upon notice, lapse of time or otherwise) any
                  holder of any other Indebtedness of the Company or any
                  Restricted Subsidiary to declare a default on such other
                  Indebtedness or cause the payment thereof to be accelerated or
                  payable prior to its stated maturity;

            (3)   any Investment in such Subsidiary deemed to be made as a
                  result of designating such Subsidiary an Unrestricted
                  Subsidiary will not violate the provisions of Section 4.7 of
                  the Indenture;

            (4)   neither the Company nor any Restricted Subsidiary has a
                  contract, agreement, arrangement, understanding or obligation
                  of any kind, whether written or oral, with such Subsidiary
                  other than (A) those that might be obtained at the time from
                  Persons who are not Affiliates of the Company or (B)
                  administrative, tax sharing and other ordinary course
                  contracts, agreements, arrangements and understandings or
                  obligations entered into in the ordinary course of business;
                  and


                                       33
<PAGE>

            (5)   neither the Company nor any Restricted Subsidiary has any
                  obligation to subscribe for additional shares of Capital Stock
                  or other Equity Interests in such Subsidiary, or to maintain
                  or preserve such Subsidiary's financial condition or to cause
                  such Subsidiary to achieve certain levels of operating results
                  other than as permitted under Section 4.7 of the Indenture.

            Notwithstanding the foregoing, the Company may not designate as an
Unrestricted Subsidiary any Subsidiary which, on the 1999 Indenture Date, was a
Significant Subsidiary, and may not sell, transfer or otherwise dispose of any
properties or assets of any such Significant Subsidiary to an Unrestricted
Subsidiary, other than in the ordinary course of business, in each case other
than Iron Mountain Global, Inc. and its Subsidiaries (including without
limitation Iron Mountain Europe Limited and its Subsidiaries).

            The Board of Directors may designate any Unrestricted Subsidiary as
a Restricted Subsidiary; provided that such designation will be deemed to be an
incurrence of Indebtedness by a Restricted Subsidiary of any outstanding
Indebtedness of such Unrestricted Subsidiary and such designation will only be
permitted if:

            (1)   such Indebtedness is permitted under Section 4.8 of the
                  Indenture and

            (2)   no Default or Event of Default would occur as a result of such
                  designation.

            (j) Limitation on Sale and Leaseback Transactions.

            Section 4.15. Limitation on Sale and Leaseback Transactions. The
Company will not, and will not permit any Restricted Subsidiary to, enter
into any Sale and Leaseback Transaction unless:

            (1)   the consideration received in such Sale and Leaseback
                  Transaction is at least equal to the fair market value of the
                  property sold, as determined by a resolution of the Board of
                  Directors and

            (2)   the Company or such Restricted Subsidiary could incur the
                  Attributable Indebtedness in respect of such Sale and
                  Leaseback Transaction in compliance with Section 4.8 of the
                  Indenture.


                                       34
<PAGE>

            (k) Asset Sales.

            Section 4.16. Asset Sales. The Company shall not, and shall not
permit any of its Restricted Subsidiaries to:

            (1)   sell, lease, convey or otherwise dispose of any assets
                  (including by way of a Sale and Leaseback Transaction, but
                  excluding a Qualifying Sale and Leaseback Transaction) other
                  than sales of inventory in the ordinary course of business
                  (provided that the sale, lease, conveyance or other
                  disposition of all or substantially all of the assets of the
                  Company will be governed by the provisions of Section 4.17 of
                  the Indenture and/or the provisions of Section 5.1 of the
                  Indenture and not by the provisions of this Section 4.16); or

            (2)   issue or sell Equity Interests of any of its Restricted
                  Subsidiaries

that in the case of either clause (1) or (2) above, whether in a single
transaction or a series of related transactions:

            (i)   have a fair market value in excess of $2.0 million or

            (ii)  result in Net Proceeds in excess of $2.0 million (each of the
                  foregoing, an "Asset Sale"), unless (x) the Company (or the
                  Restricted Subsidiary, as the case may be) receives
                  consideration at the time of such Asset Sale at least equal to
                  the fair market value (evidenced by an Officers' Certificate
                  delivered to the Trustee, and for Asset Sales having a fair
                  market value or resulting in Net Proceeds in excess of $10.0
                  million, evidenced by a resolution of the Board of Directors
                  set forth in an Officers' Certificate delivered to the
                  Trustee) of the assets sold or otherwise disposed of and (y)
                  at least 75% of the consideration therefor received by the
                  Company or such Restricted Subsidiary is in the form of cash
                  or like-kind assets (in each case as determined in good faith
                  by the Company, evidenced by a resolution of the Board of
                  Directors and certified by an Officers' Certificate delivered
                  to the Trustee);

provided, however, that the amount of

            (A)   any liabilities (as shown on the Company's or such Restricted
                  Subsidiary's most recent balance sheet or in the notes
                  thereto) of the Company or such Restricted Subsidiary (other
                  than liabilities that are by their terms subordinated to the
                  Notes or any Subsidiary Guarantee) that are assumed by the
                  transferee of any such assets and

            (B)   any notes or other obligations received by the Company or such
                  Restricted Subsidiary from such transferee that are
                  immediately converted by the Company or such Restricted
                  Subsidiary into cash (to the extent of the cash received) or
                  Cash Equivalents,

shall be deemed to be cash for purposes of this provision; and provided,
further, that the 75% limitation referred to in the foregoing clause (ii) (y)
shall not apply to any Asset Sale in which the cash portion of


                                       35
<PAGE>

the consideration received therefrom is equal to or greater than what the
after-tax proceeds would have been had such Asset Sale complied with the
aforementioned 75% limitation.

            A transfer of assets or issuance of Equity Interests by the Company
to a Wholly Owned Restricted Subsidiary or by a Wholly Owned Restricted
Subsidiary to the Company or to another Wholly Owned Restricted Subsidiary will
not be deemed to be an Asset Sale.

            Within 360 days of any Asset Sale, the Company may, at its option,
apply an amount equal to the Net Proceeds from such Asset Sale either:

            (1)   to permanently reduce Senior Debt or

            (2)   to an investment in a Restricted Subsidiary or in another
                  business or capital expenditure or other long-term/tangible
                  assets, in each case, in the same line of business as the
                  Company or any of its Restricted Subsidiaries was engaged in
                  on the date of the First Supplemental Indenture or in
                  businesses similar or reasonably related thereto.

            Pending the final application of any such Net Proceeds, the Company
may temporarily reduce Senior Bank Debt or otherwise invest such Net Proceeds in
any manner that is not prohibited by the Indenture. Any Net Proceeds from such
Asset Sale that are not applied or invested as provided in the first sentence of
this paragraph will be deemed to constitute "Excess Proceeds." When the
aggregate amount of Excess Proceeds exceeds $10.0 million, the Company shall
make an offer to all Holders of the Notes, all holders of the 9 1/8% Notes, the
8 1/4% Notes, the 8 1/8% Notes and the 8 3/4% Notes and the holders of any
future Indebtedness ranking pari passu with the Notes, which Indebtedness
contains similar provisions requiring the Company to repurchase such
Indebtedness (an "Asset Sale Offer"), to purchase the maximum principal amount
of Notes and such other Indebtedness that may be purchased out of the Excess
Proceeds, at an offer price in cash in an amount equal to 100% of the principal
amount thereof plus accrued and unpaid interest, if any, to the date of
purchase, in accordance with the procedures set forth in the Indenture;
provided, however, that prior to making any such Asset Sale Offer, the Company
may, to the extent required by the indentures for the 10 1/8% Notes or the
11 1/8% Notes, use such Excess Proceeds to repurchase the 10 1/8% Notes and the
11 1/8% Notes. To the extent that the aggregate amount of Notes and other pari
passu Indebtedness (including the 9 1/8% Notes, the 8 1/4% Notes, the 8 1/8%
Notes and the 8 3/4% Notes) tendered pursuant to an Asset Sale Offer is less
than the Excess Proceeds, the Company may use any remaining Excess Proceeds for
general corporate purposes. If the aggregate principal amount of Notes and such
other Indebtedness surrendered by Holders thereof exceeds the amount of Excess
Proceeds, the Trustee shall select the Notes and such other Indebtedness to be
purchased on a pro rata basis. Upon completion of such offer to purchase, the
amount of Excess Proceeds shall be reset at zero.

            The Company shall comply with the requirements of Rule 14e-1 under
the Exchange Act and any other securities laws and regulations thereunder to the
extent those laws and regulations are applicable in connection with each
repurchase of Notes pursuant to an Asset Sale Offer. To the extent that the
provisions of any securities laws or regulations conflict with the provisions of
this Section 4.16 of the Indenture, the Company shall comply with the applicable
securities laws and regulations and shall not be deemed to have breached its
obligations under the Asset Sale provisions of the Indenture by virtue of such
conflict.


                                       36
<PAGE>

            An Asset Sale Offer shall be made pursuant to the provisions of
Section 3.9 hereof. No later than the date which is five Business Days after the
date on which the aggregate amount of Excess Proceeds exceeds $10.0 million, the
Company shall notify the Trustee of such Asset Sale Offer and provide the
Trustee with an Officers' Certificate setting forth the calculations used in
determining the amount of Net Proceeds to be applied to the purchase of Notes.
The Company shall commence or cause to be commenced the Asset Sale Offer on a
date no later than 15 Business Days after such notice (the "Commencement Date").

            (l)   Change of Control Offer.

            Section 4.17. Change of Control Offer.

            (a) Upon the occurrence of a Change of Control, each Holder of Notes
shall have the right to require the Company to repurchase all or any part (equal
to $1,000 or an integral multiple thereof) of such Holder's Notes pursuant to
the offer described below (the "Change of Control Offer") at an offer price in
cash equal to 101% of the aggregate principal amount thereof plus accrued and
unpaid interest to but excluding the date of repurchase (the "Change of Control
Payment").

            Within 30 calendar days following any Change of Control, the Company
shall mail a notice to each Holder stating:

            (1)   that the Change of Control Offer is being made pursuant to
                  this Section 4.17 and that all Notes tendered shall be
                  accepted for payment;

            (2)   the purchase price and the purchase date, which shall be no
                  earlier than 30 calendar days nor later than 60 calendar days
                  from the date such notice is mailed (the "Change of Control
                  Payment Date");

            (3)   that any Note not tendered shall continue to accrue interest;

            (4)   that, unless the Company defaults in the payment of the Change
                  of Control Payment, all Notes accepted for payment pursuant to
                  the Change of Control Offer shall cease to accrue interest on
                  and after the Change of Control Payment Date;

            (5)   that Holders electing to have any Notes purchased pursuant to
                  a Change of Control Offer shall be required to surrender the
                  Notes, with the form entitled "Option of Holder to Elect
                  Purchase" on the reverse of the Notes completed, to the paying
                  agent at the address specified in such notice prior to the
                  close of business on the fifth Business Day preceding the
                  Change of Control Payment Date;

            (6)   that Holders will be entitled to withdraw their election if
                  the Paying Agent receives, not later than the close of
                  business on the second Business Day preceding the Change of
                  Control Payment Date, facsimile transmission or letter setting
                  forth the name of the Holder, the principal amount of Notes
                  delivered for purchase, and a statement that such Holder is
                  withdrawing its election to have such Notes purchased; and


                                       37
<PAGE>

            (7)   that Holders whose Notes are being purchased only in part will
                  be issued new Notes equal in principal amount to the
                  unpurchased portion of the Notes surrendered, which
                  unpurchased portion must be equal to $1,000 in principal
                  amount or an integral multiple thereof.

            The Company shall comply with the requirements of Rule 14e-1 under
the Exchange Act and any other securities laws and regulations thereunder to the
extent such laws and regulations are applicable to the repurchase of the Notes
in connection with a Change of Control. To the extent that the provisions of any
securities laws or regulations conflict with this Section 4.17, the Company
shall comply with the applicable securities laws and regulations and shall not
be deemed to have breached its obligations under the Indenture or the First
Supplemental Indenture by virtue of such conflict.

            (b) On the Change of Control Payment Date, the Company shall, to the
extent lawful:

            (1)   accept for payment Notes or portions thereof tendered pursuant
                  to the Change of Control Offer;

            (2)   deposit with the Paying Agent an amount equal to the Change of
                  Control Payment in respect of all Notes or portions thereof so
                  tendered; and

            (3)   deliver or cause to be delivered to the Trustee the Notes so
                  accepted together with an Officers' Certificate stating the
                  Notes or portions thereof tendered to the Company.

            The Paying Agent shall promptly mail to each Holder of Notes so
accepted the Change of Control Payment for such Notes, and the Trustee shall
promptly authenticate and mail to each Holder a new Note equal in principal
amount to any unpurchased portion of the Notes surrendered, if any; provided
that each such new Note shall be in a principal amount of $1,000 or an integral
multiple thereof. Prior to complying with the provisions of this Section 4.17,
but in any event within 90 calendar days following a Change of Control, the
Company shall either repay all outstanding Senior Debt or obtain the requisite
consents, if any, under all agreements governing outstanding Senior Debt to
permit the repurchase of Notes required by this Section 4.17. The Company shall
publicly announce in The Wall Street Journal, or if no longer published, a
national newspaper of general circulation, the results of the Change of Control
Offer on or as soon as practicable after the Change of Control Payment Date.

            The Company shall not be required to make a Change of Control Offer
upon a Change of Control if a third party makes the Change of Control Offer in
the manner, at the times and otherwise in compliance with the requirements set
forth in this Section 4.17 applicable to a Change of Control Offer made by the
Company and purchases all Notes properly tendered and not withdrawn under the
Change of Control Offer.

            (m) Corporate Existence.

            With respect to the Notes issued under this First Supplemental
Indenture, Section 4.5 of the Indenture is replaced in its entirety as follows:


                                       38
<PAGE>

            Section 4.5. Corporate Existence.

            Subject to Section 4.13 and Article V of the Indenture, as the case
may be, the Company and each of the Restricted Subsidiaries shall do or cause to
be done all things necessary to preserve and keep in full force and effect (i)
its corporate existence, and the corporate, partnership or other existence of
each of their Subsidiaries, in accordance with the respective organizational
documents (as the same may be amended from time to time) of the Company, any
such Restricted Subsidiary or any such Subsidiary, as the case may be, and (ii)
the rights (charter and statutory), licenses and franchises of the Company, the
Restricted Subsidiaries and their respective Subsidiaries; provided, however,
that the Company and the Restricted Subsidiaries shall not be required to
preserve any such right, license or franchise, or the corporate, partnership or
other existence of any of their respective Subsidiaries, if an officer of the
Company shall determine that the preservation thereof is no longer desirable in
the conduct of the business of the Company, the Restricted Subsidiaries and
their Subsidiaries, taken as a whole, and that the loss thereof is not adverse
in any material respect to the Holders of the Notes.

Section 2.7. Mergers, Consolidations or Sale of Assets.

            With respect to the Notes issued under this First Supplemental
Indenture, Section 5.1 of the Indenture is replaced in its entirety as follows:

            Section 5.1. Mergers, Consolidations or Sale of Assets.

            The Company may not consolidate or merge with or into (whether or
not the Company is the surviving corporation), or sell, assign, transfer, lease,
convey or otherwise dispose of all or substantially all of its properties or
assets in one or more related transactions, to another Person unless:

            (1)   the Company is the surviving corporation or the Person formed
                  by or surviving any such consolidation or merger (if other
                  than the Company) or to which such sale, assignment, transfer,
                  lease, conveyance or other disposition shall have been made is
                  a corporation organized or existing under the laws of the
                  United States, any state thereof or the District of Columbia;

            (2)   the Person formed by or surviving any such consolidation or
                  merger (if other than the Company) or the Person to which such
                  sale, assignment, transfer, lease, conveyance or other
                  disposition shall have been made assumes all the obligations
                  of the Company under the Notes, the First Supplemental
                  Indenture and the Indenture (pursuant to a supplemental
                  indenture in a form reasonably satisfactory to the Trustee);

            (3)   immediately after such transaction no Default or Event of
                  Default exists; and

            (4)   the Company or any Person formed by or surviving any such
                  consolidation or merger, or to which such sale, assignment,
                  transfer, lease, conveyance or other disposition shall have
                  been made, will, at the time of such transaction and after
                  giving pro forma effect thereto, be permitted to incur at
                  least $1.00 of additional Indebtedness pursuant to the test
                  set forth in the first paragraph of Section 4.8 of the
                  Indenture.


                                       39
<PAGE>

Section 2.8. Events of Default.

            With respect to the Notes issued under this First Supplemental
Indenture, Section 6.1 of the Indenture is hereby replaced in its entirety as
follows:

            Section 6.1. Events of Default.

            Each of the following constitutes an "Event of Default:"

            (1)   default for 30 days in the payment when due of interest on the
                  Notes (whether or not prohibited by the subordination
                  provisions of Article XIII of the Indenture);

            (2)   default in payment when due of the principal of or premium, if
                  any, on the Notes (whether or not prohibited by the
                  subordination provisions in Article XIII of the Indenture);

            (3)   failure by the Company to comply with Section 4.17 of the
                  Indenture;

            (4)   failure by the Company or any Guarantor for 60 days after
                  written notice from the Trustee or Holders of not less than
                  25% of the aggregate principal amount of the Notes (including
                  the Additional Notes, if any) then outstanding to comply with
                  any of its other agreements in the Indenture, the First
                  Supplemental Indenture, the Notes or the Subsidiary Guarantees
                  (in order to be effective, such notice must be in writing,
                  specify the Default, demand that it be remedied and state that
                  the notice is a "Notice of Default");

            (5)   default under any mortgage, indenture or instrument under
                  which there may be issued or by which there may be secured or
                  evidenced any Indebtedness for money borrowed by the Company
                  or any of its Restricted Subsidiaries (or the payment of which
                  is guaranteed by the Company or any of its Restricted
                  Subsidiaries) whether such Indebtedness or guarantee exists on
                  the date of the First Supplemental Indenture or is created
                  thereafter, if:

                  (i)   such default results in the acceleration of such
                        Indebtedness prior to its express maturity or shall
                        constitute a default in the payment of such Indebtedness
                        at final maturity of such Indebtedness and

                  (ii)  the principal amount of any such Indebtedness that has
                        been accelerated or not paid at maturity, when added to
                        the aggregate principal amount of all other such
                        Indebtedness that has been accelerated or not paid at
                        maturity, exceeds $10.0 million;

            (6)   a final judgment or final judgments for the payment of money
                  are entered by a court or courts of competent jurisdiction
                  against the Company or any of its Restricted Subsidiaries and
                  such judgments remain unpaid, undischarged or unstayed for a
                  period of 60 days, provided that the aggregate of all such
                  unpaid, undischaraged or unstayed judgments exceeds $10.0
                  million;


                                       40
<PAGE>

            (7)   the Company or any of its Restricted Subsidiaries that is a
                  Significant Subsidiary:

                  (i)   commences a voluntary case,

                  (ii)  consents to the entry of an order for relief against it
                        in an involuntary case,

                  (iii) consents to the appointment of a Custodian of it or for
                        all or substantially all of its property,

                  (iv)  makes a general assignment for the benefit of its
                        creditors, or

                  (v)   admits in writing that it generally is unable to pay its
                        debts as the same become due;

                  in each case, pursuant to or within the meaning of any
                  Bankruptcy Law; or

            (8)   a court of competent jurisdiction enters an order or decree
                  under any Bankruptcy Law that:

                  (i)   is for relief against the Company or any of its
                        Restricted Subsidiaries that is a Significant Subsidiary
                        in an involuntary case,

                  (ii)  appoints a Custodian of the Company or any of its
                        Restricted Subsidiaries that is a Significant Subsidiary
                        or for all or substantially all of its property, or

                  (iii) orders the liquidation of the Company or any of its
                        Restricted Subsidiaries that is a Significant
                        Subsidiary,

                  and such order or decree remains unstayed and in effect for 60
                  days; or

            (9)   except as permitted by the Indenture, the First Supplemental
                  Indenture or the Subsidiary Guarantees, any Subsidiary
                  Guarantee issued by a Restricted Subsidiary shall be held in
                  any judicial proceeding to be unenforceable or invalid or
                  shall cease for any reason to be in full force and effect, or
                  any Restricted Subsidiary or any Person acting on behalf of
                  any Restricted Subsidiary shall deny or disaffirm in writing
                  its obligations under its Subsidiary Guarantee.

The term "Bankruptcy Law" means title 11, U.S. Code or any similar Federal or
State law for the relief of debtors. The term "Custodian" means any receiver,
trustee, assignee, liquidator or similar official under any Bankruptcy Law.

Section 2.9. Acceleration.

            With respect to the Notes issued under this First Supplemental
Indenture, Section 6.2 of the Indenture is hereby replaced in its entirety as
follows:


                                       41
<PAGE>

            Section 6.2. Acceleration of Maturity.

            If any Event of Default (other than an Event of Default specified in
clauses (7)(i) through (7)(v) and (8) of Section 6.1 of the Indenture relating
to the Company or any of its Restricted Subsidiaries that is a Significant
Subsidiary) occurs and is continuing, the Trustee by notice to the Company or
the Holders of at least 25% in principal amount of the then outstanding Notes by
notice to the Company and the Trustee may declare the unpaid principal of and
any interest on all the Notes to be due and payable immediately; provided,
however, that if any Obligation with respect to Senior Bank Debt is outstanding
pursuant to the Credit Agreement upon a declaration of acceleration of the
Notes, the principal, premium, if any, and interest on the Notes will not be
payable until the earlier of:

            (1)   the day which is five Business Days after written notice of
                  acceleration is received by the Company and the Credit Agent
                  or

            (2)   the date of acceleration of the Indebtedness under the Credit
                  Agreement. If an Event of Default specified in clauses (7)(i)
                  through (7)(v) and (8) of Section 6.1 of the Indenture with
                  respect to the Company or any Restricted Subsidiary that is a
                  Significant Subsidiary occurs, the principal of, and premium,
                  if any, and any accrued and unpaid interest on all outstanding
                  Notes will become immediately due and payable without further
                  action or notice.

            In the event of a declaration of acceleration of the Notes because
an Event of Default has occurred and is continuing as a result of the
acceleration of any Indebtedness described in clause (5) of Section 6.1 of the
Indenture, the declaration of acceleration of the Notes shall be automatically
annulled if the holders of any Indebtedness described in such clause have
rescinded the declaration of acceleration in respect of such Indebtedness within
30 days from the date of such declaration and if:

            (1)   the annulment of the acceleration of the Notes would not
                  conflict with any judgment or decree of a competent
                  jurisdiction and

            (2)   all existing Events of Default, except non-payment of
                  principal or interest on the Notes that became due solely
                  because of the acceleration of the Notes, have been cured or
                  waived.

            In the case of any Event of Default occurring by reason of any
willful action (or inaction) taken (or not taken) by or on behalf of the Company
with the intention of avoiding payment of the Make Whole Price or premium, as
applicable, that the Company would have had to pay if the Company then had
elected to redeem the Notes pursuant to the optional redemption provisions of
the Indenture, the applicable Make Whole Price, or an equivalent premium, as the
case may be, shall become and be immediately due and payable to the extent
permitted by law upon the acceleration of the Notes.

Section 2.10. Amendments and Waivers.

            With respect to the Notes issued under this First Supplemental
Indenture, the following Sections replace in their entirety Sections 9.1, 9.2,
9.3 and 9.5 of the Indenture:


                                       42
<PAGE>

            Section 9.1. Without Consent of Holders.

            Notwithstanding Section 9.2 of the Indenture, without the consent of
any Holder of Notes, the Company, the Guarantors and the Trustee may amend or
supplement the Indenture or the Notes:

            (a)   to cure any ambiguity, defect or inconsistency,

            (b)   to provide for uncertificated Notes in addition to or in place
                  of certificated Notes,

            (c)   to provide for the assumption of the Company's or any
                  Guarantor's obligations to Holders of the Notes in the case of
                  a merger or consolidation,

            (d)   to make any change that would provide any additional rights or
                  benefits to the Holders of the Notes (including providing for
                  additional Subsidiary Guarantees pursuant to Section 4.13 of
                  the Indenture) or that does not materially adversely affect
                  the legal rights under the Indenture of any such Holder, or

            (e)   to comply with requirements of the SEC in order to effect or
                  maintain the qualification of the Indenture under the TIA.

            Upon the request of the Company accompanied by a resolution of its
Board of Directors authorizing the execution of any such amended or supplemental
Indenture, and upon receipt by the Trustee of the documents described in Section
7.2 of the Indenture, the Trustee shall join with the Company and the Guarantors
in the execution of any amended or supplemental Indenture authorized or
permitted by the terms of this Indenture and to make any further appropriate
agreements and stipulations that may be therein contained, but the Trustee shall
not be obligated to enter into such amended or supplemental Indenture that
affects its own rights, duties or immunities under this Indenture or otherwise.

            Section 9.2. With Consent of Holders.

            Except as provided Section 9.1 and Section 9.3 of the Indenture, the
Indenture or the Notes may be amended or supplemented with the consent of the
Holders of at least a majority in principal amount of the Notes then outstanding
(including consents obtained in connection with a tender offer or exchange offer
for Notes), and, subject to Sections 6.8 and 6.12 of the Indenture) any existing
Default or Event of Default (other than a Default or Event of Default in the
payment of the principal of, premium, if any, or interest on the Notes, except a
payment default resulting from an acceleration that has been rescinded) or
compliance with any provision of the Indenture or the Notes may be waived with
the consent of the Holders of a majority in principal amount of the then
outstanding Notes (including consents obtained in connection with a tender offer
or exchange offer for Notes).

            It shall not be necessary for the consent of the Holders of Notes
under this Section 9.2 to approve the particular form of any proposed amendment
or waiver, but it shall be sufficient if such consent approves the substance
thereof.

            Upon the request of the Company accompanied by a resolution of its
Board of Directors authorizing the execution of any such amended or supplemental
Indenture, and upon the filing with the Trustee of evidence reasonably
satisfactory to the Trustee of the consent of the Holders of Notes as


                                       43
<PAGE>

aforesaid, and upon receipt by the Trustee of the documents described in Section
7.2 hereof, the Trustee shall join with the Company and the Guarantors in the
execution of such amended or supplemental Indenture unless such amended or
supplemental Indenture affects the Trustee's own rights, duties or immunities
under this Indenture or otherwise, in which case the Trustee may in its
discretion, but shall not be obligated to, enter into such amended or
supplemental Indenture.

            Section 9.3. Limitations.

            Without the consent of each Holder affected, an amendment or waiver
may not (with respect to any Notes held by a non-consenting Holder of Notes):

            (1)   reduce the principal amount of Notes whose Holders must
                  consent to an amendment, supplement or waiver;

            (2)   reduce the principal of or change the fixed maturity of any
                  Note or alter any of the provisions with respect to the
                  redemption of the Notes in a manner adverse to the Holders of
                  the Notes;

            (3)   reduce the rate of or change the time for payment of interest
                  on any Note;

            (4)   waive a Default or Event of Default in the payment of
                  principal of or premium, if any, or interest on the Notes
                  (except a rescission of acceleration of the Notes by the
                  Holders of at least a majority in aggregate principal amount
                  of the then outstanding Notes and a waiver of the payment
                  default that resulted from such acceleration);

            (5)   make any Note payable in money other than that stated in the
                  Notes;

            (6)   make any change in the provisions of the Indenture relating to
                  waivers of past Defaults or the rights of Holders of Notes to
                  receive payments of principal of or premium, if any, or
                  interest on the Notes;

            (7)   waive a redemption payment with respect to any Note (other
                  than a payment required by Section 4.16 and Section 4.17 of
                  the Indenture);

            (8)   except pursuant to the Indenture, release any Guarantor from
                  its obligations under its Subsidiary Guarantee, or change any
                  Subsidiary Guarantee in any manner that would materially
                  adversely affect the Holders; or

            (9)   make any change in the foregoing amendment and waiver
                  provisions.

            It shall not be necessary for the consent of the Holders of Notes
under this Section 9.3 to approve the particular form of any proposed amendment
or waiver, but it shall be sufficient if such consent approves the substance
thereof.

            Section 9.5. Revocation and Effect of Consents.


                                       44
<PAGE>

            Until an amendment or waiver becomes effective, a consent to it by a
Holder of a Note is a continuing consent by the Holder and every subsequent
Holder of a Note or portion of a Note that evidences the same debt as the
consenting Holder's Note, even if notation of the consent is not made on any
Note. However, any such Holder or subsequent Holder may revoke the consent as to
his Note or portion of a Note if the Trustee receives the notice of revocation
before the date the amendment or waiver becomes effective.

            Any amendment or waiver once effective shall bind every Holder
unless it is of the type described in any of clauses (1) through (8) of Section
9.3. In that case, the amendment or waiver shall bind each Holder who has
consented to it and every subsequent Holder of a Note or portion of a Note that
evidences the same debt as the consenting Holder's Note.

Section 2.11. Subsidiary Guarantees.

            With respect to the Notes issued under this Supplemental Indenture,
Article XII of the Indenture shall apply, and the Notes shall constitute a
Series to be guaranteed by the Guarantors pursuant to Article XII of the
Indenture.

Section 2.12. Legal Defeasance and Covenant Defeasance.

            With respect to the Notes issued under this Supplemental Indenture,
Article VIII of the Indenture shall apply, and the Company shall have the option
to effect Legal Defeasance or Covenant Defeasance pursuant to Article VIII of
the Indenture. In connection with any Covenant Defeasance, the Company shall be
released from its obligations under the covenants specified in Sections 2.6 and
2.7 of this First Supplemental Indenture.

Section 2.13. Subordination.

            (a) With respect to the Notes issued under this Supplemental
Indenture, Article XIII of the Indenture shall apply, and the Notes shall be
subject to subordination pursuant to Article XIII of the Indenture. In addition,
with respect to the Notes issued under this First Supplemental Indenture, the
following Sections shall be added to Article XIII of the Indenture.

            (b) Guarantors May Consolidate, etc., on Certain Terms.

            Section 13.27. Guarantors May Consolidate, etc., on Certain Terms.

            No Guarantor shall consolidate with or merge with or into (whether
or not such Guarantor is the surviving Person), another Person whether or not it
is affiliated with such Guarantor unless (i) subject to the provisions of
Section 11.28 hereof, the Person formed by or surviving any such consolidation
or merger (if other than a Guarantor) assumes all the obligations of such
Guarantor pursuant to a supplemental indenture in form reasonably satisfactory
to the Trustee, under its Subsidiary Guarantee, the Notes and this Indenture,
(ii) immediately after giving effect to such transaction, no Default or Event of
Default exists, and (iii) such Guarantor, or any person formed by or surviving
any such consolidation or merger, will be permitted to incur, immediately after
giving effect to such transaction, at least $1.00 of additional Indebtedness
pursuant to the first paragraph of Section 4.8 hereof. In case of any such
consolidation, merger, sale or conveyance and upon the assumption by the
successor


                                       45
<PAGE>

Person, by supplemental indenture, executed and delivered to the Trustee and
satisfactory in form to the Trustee, of the Subsidiary Guarantee in this
Indenture and the due and punctual performance and observance of all of the
covenants and conditions of this Indenture to be performed by the Guarantor,
such successor Person shall succeed to and be substituted for the Guarantor with
the same effect as if it had been named herein as a Guarantor.

            (c) Releases Following Sale of Assets or Designation as Unrestricted
Subsidiary.

            Section 13.28. Releases Following Sale of Assets or Designation as
                      Unrestricted Subsidiary.

            In the event of (a) a sale or other disposition of all or
substantially all of the assets of any Guarantor, by way of merger,
consolidation or otherwise, or (b) a sale or other disposition of all of the
capital stock of any Guarantor, or (c) the designation of a Restricted
Subsidiary as an Unrestricted Subsidiary in accordance with the terms of Section
4.14 hereof, then such Guarantor (in the event of a sale or other disposition,
by way of such a merger, consolidation or otherwise, of all of the capital stock
of such Guarantor, or in the event of the designation of such Guarantor as an
Unrestricted Subsidiary) or the Person acquiring the property (in the event of a
sale or other disposition of all or substantially all of the assets of such
Guarantor) shall be released and relieved of its obligations under its
Subsidiary Guarantee; provided that the Net Proceeds of such sale or other
disposition are applied in accordance with Section 4.16 hereof.

                                   ARTICLE 3.

                                  MISCELLANEOUS

Section 3.1. Effect of Headings.

            The Article and Section headings herein are for convenience only and
shall not affect the construction hereof.

Section 3.2. Successors and Assigns.

            All covenants and agreements in this First Supplemental Indenture by
the Company shall bind its successors and assigns, whether so expressed or not.


                                       46
<PAGE>

Section 3.3. Separability Clause.

            In case any provision in this First Supplemental Indenture or in the
Notes 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.

Section 3.4. Governing Law.

            This First Supplemental Indenture and the Notes created hereby shall
be governed by and construed in accordance with the laws of the State of New
York without giving effect to any conflicts of law provisions (other than
Section 5-1401 of the New York General Obligations Law) that might cause this
First Supplemental Indenture and the Notes to be governed by or construed or
enforced in accordance with the laws of any other jurisdiction.

Section 3.5. First Supplement to Supersede Indenture.

            The Indenture, as supplemented by the First Supplemental Indenture,
remains in full force and effect as of the date hereof. Notwithstanding the
foregoing, to the extent that any provision of the Indenture shall conflict with
any provision of this First Supplemental Indenture, the terms of this First
Supplemental Indenture shall be deemed controlling and the conflicting provision
of the Indenture shall be null and void to the extent of such conflict.

           [The rest of this page has been intentionally left blank.]


                                       47
<PAGE>

            IN WITNESS WHEREOF, the parties have caused this First Supplemental
Indenture to be duly executed, and attested, all as of the date and year first
written above.

                             IRON MOUNTAIN INCORPORATED

                             By: /s/ C. Richard Reese
                                 -----------------------------------------------
                                 Name: C. Richard Reese
                                 Title: Chairman and Chief Executive Officer


                             ARCUS DATA SECURITY, INC.
                             COMAC, INC.
                             DSI TECHNOLOGY ESCROW SERVICES, INC.
                             IM BILLERICA, INC.
                             IRON MOUNTAIN GLOBAL, INC.
                             IRON MOUNTAIN RECORDS MANAGEMENT, INC.
                             IRON MOUNTAIN RECORDS MANAGEMENT OF MICHIGAN, INC.

                             By: /s/ C. Richard Reese
                                 -----------------------------------------------
                                 Name: C. Richard Reese
                                 Title: Chairman and Chief Executive Officer


                             IRON MOUNTAIN/NATIONAL UNDERGROUND STORAGE, LLC
                             IRON MOUNTAIN CONSULTING SERVICES, LLC
                             IRON MOUNTAIN CONFIDENTIAL DESTRUCTION LLC

                             By: Iron Mountain Records Management, Inc.,
                                 its sole Member

                                 By: /s/ C. Richard Reese
                                     -------------------------------------------
                                     Name: C. Richard Reese
                                     Title: Chairman and Chief Executive Officer

                           [Indenture Signature Page]

<PAGE>

                             IRON MOUNTAIN GLOBAL LLC

                             By: Iron Mountain Global, Inc., its sole Member

                                 By: /s/ C. Richard Reese
                                     -------------------------------------------
                                     Name: C. Richard Reese
                                     Title: Chairman and Chief Executive Officer


                             ARCUS DATA SECURITY LLC

                             By: Arcus Data Security, Inc., its sole Member

                                 By: /s/ C. Richard Reese
                                     -------------------------------------------
                                     Name: C. Richard Reese
                                     Title: Chairman and Chief Executive Officer


                             THE BANK OF NEW YORK, as Trustee

                             By: /s/ Kisha A. Holder
                                 -----------------------------------------------
                                 Name: Kisha A. Holder
                                 Title: Assistant Treasurer

                  [First Supplemental Indenture Signature Page]

<PAGE>

                                                                       Exhibit A

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

                                 [Face of Note]
                    8 5/8% Senior Subordinated Notes due 2013

No. ___________________                                         $_______________

                           IRON MOUNTAIN INCORPORATED

promises to pay to _____________ or registered assigns, the principal sum of
___________________ Dollars on April 1, 2013.

            Interest Payment Dates: April 1 and October 1

            Record Dates: March 15 and September 15

            Dated: April [ ], 2001

            CUSIP No. ________________

                                                IRON MOUNTAIN INCORPORATED


                                                By:   __________________________
                                                Name:
                                                Title:


                                                By:   __________________________
                                                Name:
                                                Title:

                                     (SEAL)

This is one of the Notes
referred to in the within-
mentioned Indenture:

THE BANK OF NEW YORK,
as Trustee


By: __________________________
       Authorized Signature

<PAGE>

                                 [Back of Note]
                    8 5/8% Senior Subordinated Notes due 2013

            [INSERT IN GLOBAL NOTES] [This Security is a Global Security within
the meaning of the Indenture hereinafter referred to and is registered in the
name of the Depository or a nominee of the Depository. This Security is
exchangeable for Securities registered in the name of a person other than the
Depository or its nominee only in the limited circumstances described in the
Indenture, and may not be transferred except as a whole by the Depository to a
nominee of the Depository, by a nominee of the Depository to the Depository or
another nominee of the Depository or by the Depository or any such nominee to a
successor Depository or a nominee of such a successor Depository.]

            Unless and until it is exchanged in whole or in part for Notes in
definitive form, this Note may not be transferred except as a whole by the
Depository to a nominee of the Depository or by a nominee of the Depository to
the Depository or another nominee of the Depository or by the Depository or any
such nominee to a successor Depository or a nominee of such successor
Depository. Unless this certificate is presented by an authorized representative
of The Depository Trust Company (55 Water Street, New York, New York) ("DTC"),
to the issuer or its agent for registration of transfer, exchange or payment,
and any certificate issued is registered in the name of Cede & Co. or such other
name as may be requested by an authorized representative of DTC (and any payment
is made to Cede & Co. or such other entity as may be requested by an authorized
representative of DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner
hereof, Cede & Co., has an interest herein.

            Capitalized terms used herein shall have the meanings assigned to
them in the Indenture referred to below unless otherwise indicated.

            1. INTEREST. Iron Mountain Incorporated, a Pennsylvania corporation
(the "Company") promises to pay interest on the principal amount of this Note at
8 5/8% per annum from April [ ], 2001 until April 1, 2013. The Company shall pay
interest, semi-annually in arrears on April 1 and October 1 of each year, or if
any such day is not a Business Day, on the next succeeding Business Day (each an
"Interest Payment Date"). Interest on the Notes will accrue from the most recent
date to which interest has been paid or, if no interest has been paid, from the
date of issuance; provided that if there is no existing Default in the payment
of interest, and if this Note is authenticated between a record date referred to
on the face hereof and the next succeeding Interest Payment Date, interest shall
accrue from such next succeeding Interest Payment Date; provided, further, that
the first Interest Payment Date shall be October 1, 2001. The Company shall pay
interest (including post-petition interest to the extent allowed in any
proceeding under any Bankruptcy Law) on overdue principal from time to time on
demand at a rate equal to the per annum rate on the Notes then in effect; it
shall pay interest (including post-petition interest to the extent allowed in
any proceeding under any Bankruptcy Law) on overdue installments of interest
(without regard to any applicable grace periods) from time to time on demand at
the same rate to the extent lawful. Interest will be computed on the basis of a
360-day year of twelve 30-day months.

            2. METHOD OF PAYMENT. The Company will pay principal and interest in
money of the United States that at the time of payment is legal tender for
payment of public and private debts. The Company, however, may pay principal,
premium, if any, and interest by check payable in such money. It may mail an
interest check to a Holder's registered address.

<PAGE>

            3. PAYING AGENT, REGISTRAR AND SERVICE AGENT. Initially, The Bank of
New York, the Trustee under the Indenture, will act as Paying Agent, Registrar
and Service Agent. The Notes may be presented for registration of transfer and
exchange at the offices of the Registrar. The Company may change any Paying
Agent, Service Agent or Registrar without notice to any Holder. The Company or
any of its Subsidiaries may act in any such capacity.

            4. INDENTURE. The Company issued the Notes under an Indenture
dated as of April 3, 2001 (the "Base Indenture") as supplemented by a First
Supplemental Indenture dated as of April 3, 2001 (the "Supplemental
Indenture" and, together with the Base Indenture, the "Indenture") among the
Company, the Guarantors and the Trustee. The terms of the Notes include those
stated in the Indenture and those made part of the Indenture by reference to
the Trust Indenture Act of 1939, as amended (15 U.S. Code Sections
77aaa-77bbbb). The Notes are subject to all such terms, and Holders are
referred to the Indenture and such Act for a statement of such terms. The
terms of the Indenture shall govern any inconsistencies between the Indenture
and the Notes. The Notes issued under the Indenture are subordinated
unsecured obligations of the Company limited to $500,000,000 in aggregate
principal amount.

            5. OPTIONAL REDEMPTION.

            Prior to April 1, 2006, the Notes will be subject to redemption at
any time at the option of the Company, in whole or in part, upon not less than
30 nor more than 60 days' notice, at the Make-Whole Price, plus accrued and
unpaid interest thereon to the applicable redemption date. At any time on or
after April 1, 2006, the Company may redeem any portion of the Notes, in whole
or in part, on at least 30 days, but no more than 60 days' notice at the
following prices (expressed as a percentage of the principal amount), together
with accrued and unpaid interest to, but excluding, the redemption date:

                  Redemption Period                             Redemption Price
                  -----------------                             ----------------

April 1, 2006 to March 31, 2007.............................        104.313%
April 1, 2007 to March 31, 2008.............................        102.875%
April 1, 2008 to March 31, 2009                                     101.438%
April 1, 2009 and thereafter................................        100.000%

            Notwithstanding the foregoing, at any time prior to April 1, 2004,
the Company may redeem up to 35% of the initial principal amount of the Notes
originally issued with the net proceeds of one or more Qualified Equity
Offerings at a redemption price equal to 108.625% of the principal amount of
such Notes, plus accrued and unpaid interest to the date of redemption;
provided, that at least 65% of the principal amount of Notes originally issued
remains outstanding immediately after the occurrence of any such redemption and
that such redemption occurs within 60 days following the closing of any such
Qualified Equity Offering.

            6. NOTICE OF REDEMPTION.

            Notice of redemption will be mailed at least 30 days but not more
than 60 days before the redemption date to each Holder of the Notes to be
redeemed at such Holder's address of record. The Notes in denominations larger
than $1,000 may be redeemed in part but only in integral multiples of $1,000,
unless all the Notes held by a Holder are to be redeemed. In the event of a
redemption of less than all of the Notes, the Notes will be chosen for
redemption by the Trustee in accordance with the

<PAGE>

Indenture. On and after the redemption date, interest ceases to accrue on the
Notes or portions of them called for redemption.

            If this Note is redeemed subsequent to a Record Date with respect to
any Interest Payment Date specified above and on or prior to such Interest
Payment Date, then any accrued interest will be paid to the Person in whose name
this Note is registered at the close of business on such Record Date.

            7. MANDATORY REDEMPTION. Except as set forth in paragraph 8 below,
the Company shall not be required to make mandatory redemption payments with
respect to the Notes. There are no sinking fund payments with respect to the
Notes.

            8. REPURCHASE AT OPTION OF HOLDER. This Note is subject to purchase
at the option of the Holder upon the circumstances set forth in Sections 3.9,
4.16 and 4.17 of the Indenture.

            9. SUBORDINATION. The payment of the principal of, interest on or
any other amounts due on the Notes is subordinated in right of payment to all
existing and future Senior Debt of the Company, as described in the Indenture.
Each Holder, by accepting a Note, agrees to such subordination and authorizes
and directs the Trustee on its behalf to take such action as may be necessary or
appropriate to effectuate the subordination so provided and appoints the Trustee
as its attorney-in-fact for such purpose.

            10. DENOMINATIONS, TRANSFER, EXCHANGE. The Notes are in registered
form without coupons in minimum denominations of $1,000 and integral multiples
of $1,000 in excess thereof. The transfer of Notes may be registered and Notes
may be exchanged as provided in the Indenture.

            11. PERSONS DEEMED OWNERS. Prior to due presentment to the Trustee
for registration of the transfer of this Note, the Trustee, any Agent, the
Company and the Guarantors may deem and treat the Person in whose name this Note
is registered as its absolute owner for the purpose of receiving payment of
principal of, premium, if any, and interest on this Note and for all other
purposes whatsoever, whether or not this Note is overdue, and none of the
Trustee, any Agent, the Company or any Guarantor shall be affected by notice to
the contrary. The registered Holder of a Note may be treated as its owner for
all purposes.

            12. AMENDMENT, SUPPLEMENT AND WAIVER. Subject to certain exceptions,
the Indenture with respect to the Notes or the Notes may be amended or
supplemented with the written consent of the Holders of a majority in principal
amount of the then outstanding Notes, and any existing default or compliance
with any provision of the Indenture with respect to the Notes or the Notes may
be waived with the consent of the Holders of a majority in principal amount of
the Notes (including, in each case, Additional Notes, if any). Without the
consent of any Holder of the Notes, the Indenture with respect to the Notes or
the Notes may be amended or supplemented to, in addition to other events more
fully described in the Indenture, cure any ambiguity, defect or inconsistency,
provide for uncertificated Notes in addition to or in place of certificated
Notes, provide for the assumption of the Company's or a Guarantor's obligations
to Holders of the Notes in the case of a merger or consolidation, make any
change that would provide any additional rights or benefits to the Holders of
the Notes or that does not materially adversely affect the legal rights under
the Indenture of any such Holder, or comply with requirements of the SEC in
order to effect or maintain the qualification of the Indenture under the TIA.

            13. DEFAULTS AND REMEDIES. An Event of Default with respect to the
Notes includes: the default for 30 days in the payment when due of interest on
the Notes (whether or not prohibited by the subordination provisions of the
Indenture); the default in payment when due of the principal of or premium, if
any, on the Notes (whether or not

<PAGE>

prohibited by the subordination provisions of the Indenture); the failure by the
Company to comply with Section 4.17 of the Indenture; the failure by the Company
or any Guarantor for 60 days after written notice from the Trustee or Holders of
not less than 25% of the aggregate principal amount of the Notes (including
Additional Notes, if any) outstanding to comply with any of its other agreements
in the Indenture, Notes or the Subsidiary Guarantees; the default under any
mortgage, indenture or instrument under which there may be issued or by which
there may be secured or evidenced any Indebtedness for money borrowed by the
Company or any of its Restricted Subsidiaries (or the payment of which is
guaranteed by the Company or any of its Restricted Subsidiaries) whether such
Indebtedness or guarantee exists on the date of the Indenture or is created
thereafter, if: (i) such default results in the acceleration of such
Indebtedness prior to its express maturity or shall constitute a default in the
payment of such Indebtedness at final maturity of such Indebtedness and (ii) the
principal amount of any such Indebtedness that has been accelerated or not paid
at maturity, when added to the aggregate principal amount of all other such
Indebtedness that has been accelerated or not paid at maturity, exceeds $10.0
million; the failure by the Company or any of its Restricted Subsidiaries to pay
final judgments aggregating in excess of $10.0 million, which judgments remain
unpaid, undischarged or unstayed for a period of 60 days; certain events of
bankruptcy or insolvency with respect to the Company or any of its Restricted
Subsidiaries that is a Significant Subsidiary; or except as permitted by the
Indenture or the Subsidiary Guarantees, any Subsidiary Guarantee issued by a
Restricted Subsidiary shall be held in any judicial proceeding to be
unenforceable or invalid or shall cease for any reason to be in full force and
effect, or any Restricted Subsidiary or any Person acting on behalf of any
Restricted Subsidiary shall deny or disaffirm in writing its obligations under
its Subsidiary Guarantee.

            If any Event of Default occurs and is continuing, the Trustee or the
Holders of at least 25% in principal amount of the then outstanding Notes
(including Additional Notes, if any) may declare all the Notes to be due and
payable immediately; provided, however, that if any Obligation with respect to
Senior Bank Debt is outstanding pursuant to the Credit Agreement upon a
declaration of acceleration of the Notes, the principal, premium, if any, and
interest on the Notes will not be payable until the earlier of: (1) the day
which is five business days after written notice of acceleration is received by
the Company and the Credit Agent or (2) the date of acceleration of the
Indebtedness under the Credit Agreement. Notwithstanding the foregoing, in the
case of an Event of Default arising from certain events of bankruptcy or
insolvency with respect to the Company or any Restricted Subsidiary that is a
Significant Subsidiary, the principal of, and premium, if any, and any accrued
and unpaid interest on all outstanding Notes will become due and payable without
further action or notice. In the event of a declaration of acceleration of the
Notes because an Event of Default has occurred and is continuing as a result of
the acceleration of any Indebtedness described in Section 6.1(5) of the
Indenture, the declaration of acceleration of the Notes shall be automatically
annulled if the holders of any Indebtedness described in such section have
rescinded the declaration of acceleration in respect of such Indebtedness within
30 days from the date of such declaration and if: (1) the annulment of the
acceleration of the Notes would not conflict with any judgment or decree of a
competent jurisdiction and (2) all existing Events of Default, except
non-payment of principal or interest on the Notes that became due solely because
of the acceleration of the Notes, have been cured or waived.

            Subject to certain limitations, Holders of a majority in principal
amount of the then outstanding Notes may direct the Trustee in its exercise of
any trust or power. The Trustee may withhold from Holders of the Notes notice of
any continuing Default or Event of Default (except a Default or Event of Default
relating to the payment of principal or interest) if it determines that
withholding notice is in their interest. The Company is required to deliver to
the Trustee annually a statement regarding compliance with the Indenture, and
the Company is required, upon becoming aware of any Default or

<PAGE>

Event of Default, to deliver to the Trustee a statement specifying such Default
or Event of Default and what action the Company is taking or proposes to take
thereto.

            14. SUBSIDIARY GUARANTEES. Payment of principal of, premium, if any,
and interest (including interest on overdue principal, premium, if any, and
interest, if lawful) on the Notes is guaranteed on an unsecured, senior
subordinated basis by the Guarantors pursuant to Article XII of the Indenture.

            15. TRUSTEE DEALINGS WITH COMPANY. The Trustee, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company or its Affiliates, and may otherwise deal with the
Company or its Affiliates, as if it were not the Trustee.

            16. NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator or stockholder, as such, of the Company or any
Guarantor shall have any liability for any obligations of the Company or any
Guarantor under the Notes, the Subsidiary Guarantees or the Indenture or for any
claim based on, in respect of or by reason of such obligations or their
creation. Each Holder by accepting a Note and the related Subsidiary Guarantees
waives and releases all such liability. The waiver and release are part of the
consideration for the issuance of the Notes.

            17. AUTHENTICATION. This Note shall not be valid until authenticated
by the manual signature of the Trustee or an authenticating agent.

            18. ABBREVIATIONS. Customary abbreviations may be used in the name
of a Holder or an assignee, such as: TEN COM (= tenants in common), TEN ENT (=
tenants by the entireties), JT TEN (= joint tenants with right of survivorship
and not as tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform Gifts
to Minors Act).

            19. CUSIP NUMBERS. Pursuant to a recommendation promulgated by the
Committee on Uniform Security Identification Procedures, the Company has caused
CUSIP numbers to be printed on the Notes and the Trustee may use CUSIP numbers
in notices of redemption as a convenience to Holders. No representation is made
as to the accuracy of such numbers either as printed on the Notes or as
contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon.

            The Company shall furnish to any Holder upon written request and
without charge a copy of the Indenture. Requests may be made to:

                   Iron Mountain Incorporated
                   745 Atlantic Avenue
                   Boston, Massachusetts 02111
                   Attention: Chief Financial Officer

<PAGE>

                                 ASSIGNMENT FORM

To assign this Note, fill in the form below: (I) or (we) assign and transfer
this Note to

--------------------------------------------------------------------------------
                  (Insert assignee's soc. sec. or tax I.D. no.)

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
              (Print or type assignee's name, address and zip code)

and irrevocably appoint ________________________________________________________
to transfer this Note on the books of the Company. The agent may substitute
another to act for him.

Date: __________

Your Signature: ________________________________________________________________
(Sign exactly as your name appears on the face of this Note)

Signature Guarantee:

<PAGE>

                       OPTION OF HOLDER TO ELECT PURCHASE

            If you want to elect to have this Note purchased by the Company
pursuant to Section 4.16 or 4.17 of the Indenture, check the box below:

                  |_| Section 4.16

                  |_| Section 4.17

            If you want to elect to have only part of the Note purchased by the
Company pursuant to Section 4.16 or 4.17 of the Indenture, state the amount you
elect to have purchased: $________


Date: __________                 Your Signature: _______________________________
                                 (Sign exactly as your name appears on the Note)

                                 Tax Identification No.: _______________________

Signature Guarantee:

<PAGE>

                         SCHEDULE OF EXCHANGES OF NOTES

            The following exchanges of a part of this Global Note for Definitive
Notes have been made:

<TABLE>
<CAPTION>
                                                                      Principal Amount of       Signature of
                      Amount of decrease    Amount of increase in      this Global Note       authorized office
                      in Principal Amount    Principal Amount of        following such          of Trustee or
Date of Exchange      of this Global Note      this Global Note     decrease (or increase)      Service Agent
----------------      -------------------      ----------------     ----------------------      -------------
<S>                   <C>                   <C>                     <C>                       <C>
</TABLE>

<PAGE>

                                    EXHIBIT B

       FORM OF SUPPLEMENTAL INDENTURE TO BE DELIVERED BY FUTURE GUARANTORS

            SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of
________________, _____, between __________________ (the "Guarantor"), a
subsidiary of Iron Mountain Incorporated (or its successor), a Pennsylvania
corporation (the "Company"), and The Bank of New York, a New York banking
corporation, as trustee under the Indenture referred to below (the "Trustee").

                               W I T N E S S E T H

            WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture, dated as of April 3, 2001, as supplemented by the First
Supplemental Indenture, dated as of April 3, 2001 (the indenture, as so
supplemented, the "Indenture") providing for the issuance of an aggregate
principal amount of $225,000,000 of 8"% Senior Subordinated Notes due 2013 (the
"Notes");

            WHEREAS, Section 4.13 of the Indenture provides that under certain
circumstances the Company is required to cause the Guarantor to execute and
deliver to the Trustee a supplemental indenture pursuant to which the Guarantor
shall unconditionally guarantee all of the Company's obligations under the Notes
pursuant to a Subsidiary Guarantee on the terms and conditions set forth herein;
and

            WHEREAS, pursuant to Section 9.1 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

            NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Guarantor and the Trustee mutually covenant and agree for the equal and ratable
benefit of the Holders of the Notes as follows:

      1. CAPITALIZED TERMS. Capitalized terms used herein without definition
shall have the meanings assigned to them in the Indenture.

      2. AGREEMENT TO GUARANTEE. The Guarantor hereby agrees that its
obligations to the Holder and the Trustee pursuant to this Subsidiary Guarantee
shall be as expressly set forth in Article XII of the Indenture and in such
other provisions of the Indenture as are applicable to the Guarantors
(including, without limitation, Article XIII of the Indenture), and reference is
made to the Indenture for the precise terms of this Supplemental Indenture. The
terms of Article XII of the Indenture and such other provisions of the Indenture
(including, without limitation, Article XIII of the Indenture) as are applicable
to the Guarantors are incorporated herein by reference.

      3. EXECUTION AND DELIVERY OF SUBSIDIARY GUARANTEES.

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            (a) If an Officer whose signature is on this Supplemental Indenture
      no longer holds that office at the time the Trustee authenticates the
      Note, the Subsidiary Guarantee shall be valid nevertheless.

            (b) The delivery of any Note by the Trustee, after the
      authentication thereof under the Indenture, shall constitute due delivery
      of the Subsidiary Guarantee set forth in this Supplemental Indenture on
      behalf of the Guarantor.

      4. NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator, stockholder of the Guarantor, as such, shall
have any liability for any obligations of the Company or any Guarantor under the
Notes, any Subsidiary Guarantee, the Indenture or this Supplemental Indenture or
for any claim based on, in respect of, or by reason of, such obligations or
their creation. Each Holder of the Notes by accepting a Note waives and releases
all such liability. The waiver and release are part of the consideration for
issuance of the Notes.

      5. NEW YORK LAW TO GOVERN. The internal law of the State of New York shall
govern and be used to construe this Supplemental Indenture and the Subsidiary
Guarantee.

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

      7. EFFECT OF HEADINGS. The Section headings herein are for convenience
only and shall not affect the construction hereof.


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            IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed, all as of the date first above written.

Dated: _______________, _______
                                          [Guarantor]

                                          By: __________________________________
                                              Name:
                                              Title:

Dated: _______________, _______
                                          The Bank of New York

                                          By: __________________________________
                                              Name:
                                              Title:


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