Patent Publication Number: US-7720818-B1

Title: On-line account management system having a tiered account information storage system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is related to co-pending U.S. patent application Ser. Nos. 10/331,427 entitled “On-Line Account Management System Having A Synchronized Account Information Data Store” and 10/331,318 entitled “Method For Transporting Billing Information To An On-Line Account Management System”, both of which were filed on even date herewith, assigned to the Assignee of the present application and hereby incorporated by reference as if reproduced in their entirety. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   REFERENCE TO A MICROFICHE APPENDIX 
   Not applicable. 
   FIELD OF THE INVENTION 
   The invention is directed to a system and method for on-line management of account information by customers of a provider of goods or services to a service and, more particularly, to a tiered storage system, partially accessible to subscribers, which maintains the account information to be managed. By periodically shifting excessively aged invoices into an indexed lower tier, the storage system is capable of maintaining subscriber access to larger amounts of the invoice information without a corresponding consumption of additional memory resources. 
   BACKGROUND OF THE INVENTION 
   Traditionally, telecommunication service providers and other corporate entities have maintained account information for their subscribers or other customers on an internal enterprise network typically configured to include a mainframe or other large scale computing device in which the account information was maintained and plural client computing devices capable of accessing information maintained on the mainframe. In contrast with a traditionally configured limited access enterprise network such as the one herein described, the Internet is a vast, publicly accessible computer network comprised of a wide variety of disparate computing devices operated by an equally disparate group of computer users. These computing devices are interconnected by various connection media which communicate using the transmission control protocol/Internet protocol (“TCP/IP”) set of communication protocols. 
   In recent years, it has become increasingly commonplace for commercial enterprises such as corporations to interconnect their limited access enterprise network with the Internet. The purpose of such interconnections was two-fold—to enable the users of the enterprise network access to resources available through the Internet and to enable external computer users to access selected resources of the enterprise network through the Internet through a computer system commonly referred to as a web server. As the corporate web server became more common, information which was traditionally maintained on the mainframe where it could only be accessed by employees through the enterprise network began to migrate onto the web server. As a result, while a web server typically maintains publicly available content, oftentimes, it will also maintain content for which access is limited to authorized users. For example, a telecommunications service provider may have a web site which provides general information on its services within a publicly accessible portion of the site while allowing existing subscribers to access confidential information, typically, their personal account information, within a limited access portion of the site to which unrelated third parties are barred. 
   Early web sites were quite rudimentary, with only a limited amount of functionality available to the accessing subscriber. As the web sites became more sophisticated, however, additional subscriber functionality was added to the sites. Similarly, as subscribers became more “web-savvy”, their expectations of what subscriber functionality should be available at the sites grew. Over time, it became common for a web site to allow a subscriber to review invoices, update subscriber information and make payments on-line. However, certain limitations have prevented web sites from performing these and other tasks effectively. For example, to place invoices on-line, it was common for the service provider to employ software which electronically searches through text images of the printed invoices for information of interest, captures selected information from the text images of the printed invoices and reformat the captured information to create electronic invoices. This technique is both complex and difficult to maintain. For example, if the name of a product or service is changed, the software employed by the service provider must be updated in order to be able to continue to capture invoice information associated with the re-named product or service. 
   It also became desirable for the service provider to place account receivable (“A/R”) information on the web site. Unlike invoice information which, once generated, remains unchanged, A/R information is constantly updated. For example, a subscriber may be billed on the first of the month, receive a partial credit for a wrong number on the tenth of the month and pay the balance owed on their account on the twentieth of the month. Thus, any A/R information to be maintained on the web site must be constantly updated by the mainframe in order to be accurate. Otherwise, the subscriber accessing A/R information through the web site would view outdated information. However, a significant amount of resources may be consumed by the heavy traffic resulting from the constant updating or “synchronizing” necessary such that the A/R information residing on the web server matches that residing on the mainframe. 
   Another problem with maintaining invoice, A/R and similar types of subscriber information on the web site relates to the substantial consumption of memory resources at the web site which results from maintaining these types of subscriber information at the web site. For example, a service provider typically generates a new invoice for each customer on a monthly basis. It should be readily appreciated, therefore, that maintaining invoice information on-line will quickly consume the available memory resources, particularly if the service provider has hundreds of thousands of subscribers. To conserve existing memory resources and avoid the added expense of additional memory resources, many web sites which maintain invoice information on-line will typically limit the number of months of invoice information available over the web. For example, many sites limit available invoice information to only two months and will delete aged invoice information to free space for newer invoice information. While such an approach both keeps the information which tends to be of most interest to subscribers while restraining the cost of maintaining invoice information on-line, it does limit the usefulness of the web site since subscribers interested in older invoices are forced to contact a representative of the service provider capable of retrieving the desired invoice information off the mainframe computer system. 
   By configuring a web site to include a tiered storage system in which current information is maintained in an upper tier while older information is maintained in an indexed lower tier, a subscriber would be capable of accessing account information which encompasses a greater chronological period. It is, therefore, the object of the invention to provide such a storage system. 
   SUMMARY OF THE INVENTION 
   In one embodiment, the present invention is directed to an account management system which includes a tiered memory system for maintaining account records for customers of a provider of goods or services, a processor subsystem coupled to the tiered memory subsystem and an account management application residing within the processor subsystem. The tiered memory subsystem maintains account records within a first age range in a first tier of the tiered memory subsystem and compressed account records within a second age range in a second tier of the tiered memory subsystem. Customers accessing the account management application via a network may view the account records maintained in the first tier of the tiered memory subsystem but cannot view the compressed account records maintained in the second tier of the tiered memory subsystem. 
   In one aspect of this embodiment of the invention, the first tier of the tiered memory subsystem is a database and the second tier of the tiered memory subsystem is a flat file. In another, the tiered memory subsystem includes a third tier for maintaining compressed account records within a third age range. In this aspect, at least a portion of the third tier of the tiered memory subsystem is removably coupleable to the processor subsystem. In a further aspect thereof, the first tier of the tiered memory subsystem is a database, the second tier of the tiered memory subsystem is a flat file and the third tier of the tiered memory subsystem includes at least one tape. 
   In another aspect of the aforementioned embodiment of the invention, the account management system further includes an archival application residing in the processor subsystem. In this aspect, the archival application attends to the compression and transfer of account records from the first tier of the tiered memory subsystem to the second tier of the tiered memory subsystem when the account records age from a first age within the first age range to a second age within the second age range. In still another aspect thereof, the account management system further includes a retrieval application residing within the processor subsystem. In this aspect, the retrieval application attends to decompression and restoration of selected account records, maintained in the second tier of the tiered memory subsystem, to the first tier of the tiered memory subsystem in response to a request, by the account management application, to restore the selected account records to the first tier of the tiered memory subsystem. In either of the former or the latter aspects, the first tier of the tiered memory subsystem is a database and the second tier of the tiered memory subsystem is a flat file. For the latter aspect, the first tier of the tiered memory subsystem may also include a database in which the account records within the first age range are maintained and a data file in which an index to the compressed account records maintained in the second tier of the tiered memory subsystem is maintained. 
   In still further aspects thereof, the second tier of the tiered memory subsystem may include at least one flat file in which the compressed account records within the second age range are maintained; the account records in the first tier of the tiered memory subsystem may be arranged by customer and time of generation; and the account records in the second tier of the tiered memory subsystem may be sequentially arranged by time of transfer to the second tier of the tiered memory subsystem. In still another aspect thereof, the archival application may construct, for each account record compressed and transferred from the first tier of the tiered memory subsystem to the second tier of the tiered memory subsystem, a corresponding entry for inclusion in the index. In this aspect, each entry in the index would identify a location, by flat file and offset within the flat file, within the second tier of the tiered memory subsystem, where the corresponding compressed account record is located. Finally, in still another aspect thereof, each entry in the index would further identify the customer for which the corresponding account record was generated and the time at which the corresponding account record was generated. 
   In another embodiment, the present invention is directed to an on-line account management system which includes a tiered memory subsystem for maintaining account records for customers of a provider of goods or services, a processor subsystem coupled to the tiered management system, an account management application residing within the processor subsystem and an archival application residing within the processor subsystem. The tiered memory subsystem maintains: (1) account records within a first age range in a first tier of the tiered memory subsystem; (2) compressed account records within a second age range in a second tier of the tiered memory subsystem; and (3) compressed account records within a third age range in a third tier of the tiered memory subsystem. The archival application automatically executes a first routine at a first pre-determined frequency and a second routine at a second pre-determined frequency. During each execution of the first routine, the archival application identifies account records having aged from a first age within the first age range to a second age within the second age range, compresses the identified account records and places the compressed account records in flat files, created by the archival application, in the second tier of the tiered memory subsystem. During each execution of the second routine, the archival application determines, for each flat file created and filled thereby, whether the flat file should be transferred from the second tier of the tiered memory subsystem to the third tier of the memory subsystem. 
   In one aspect of this embodiment of the invention, the archival application determines whether the flat file should be transferred from the second tier of the tiered memory subsystem to the third tier of the tiered memory subsystem based upon a comparison, for the flat file, of the total number of customers having compressed account records within the third age range to the total number customers having compressed accounts. In a further aspect of this embodiment, the first age range is less than three months, the second age range is three to twelve months and the third age range is greater than twelve months. 
   In another aspect of this embodiment of the invention, the first tier of the tiered memory subsystem is a database, the second tier of the tiered memory subsystem is a data space sub-divided, by the archival application, into at least one flat file and the third tier of the tiered memory subsystem includes at least one tape. In another, the account management application further includes a retrieval application residing within the processor subsystem. In this aspect, the retrieval application attends to the decompression and restoration of selected account records, maintained in the second tier of the tiered memory subsystem, to the first tier of the tiered memory subsystem in response to a request, by the account management application to restore the selected account records to the first tier of the tiered memory subsystem. In further accordance with this aspect, the first tier of the tiered memory subsystem may also include an index file to the compressed account records maintained in the second tier of the tiered memory subsystem. In this aspect, the archival application creates an entry, in the index file, for each account record archived in the second tier of the tiered memory subsystem thereby and the retrieval application uses the index file created by the archival application to locate the compressed account records archived in the second tier of the tiered memory subsystem and subsequently selected for restoration to the first tier of the memory subsystem. 
   In still another embodiment, the present invention is directed to a method of providing customer access to account information over a network. In accordance with the disclosed method, a tiered memory system and an archival/retrieval application are constructed. The tiered memory system includes a customer accessible first tier in which account records within a first age range are maintained and a customer inaccessible second tier in which compressed account records within a second age range are maintained. The archival/retrieval application controls the transfer of account records between the first and second tiers of the tiered memory system. Customers may view their account records while they are maintained in the first tier of the tiered memory system. Periodically, however, the archival/retrieval application removes account records from the first tier of the tiered memory system for compression and subsequent archival in the second tier of the tiered memory system. Account records are removed for compression and subsequent archival upon the archival/retrieval application determining that the account records have aged from a first age within the first age range to a second age within the second age range. While compressed account records cannot be viewed by a customer while the account records are maintained in the second tier of the tiered memory system, in response to a customer request, the compressed account records maintained in the second tier of the tiered memory system may be decompressed and subsequently placed in the first tier of the tiered memory system. Accordingly, customers may view account records within the first age range and requested account records within the second age range over the network. 
   In one aspect of this embodiment of the invention, during the removal of account records from the first tier of the tiered memory system, the archival/retrieval application may construct an index file having, for each account record removed from the first tier of the tiered memory system and archived in the second tier of the tiered memory system, the location of the account record in the second tier of the tiered memory system. In a further aspect of this embodiment of the invention, the compressed account records maintained in the second tier of the tiered memory system and retrieved, by the archival/retrieval application for decompression and subsequent placement in the first tier of the tiered memory system, are retrieved using the index file to locate each account record, maintained in the second tier of the tiered memory system, to be placed in the first tier of the tiered memory system. 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is a block diagram of a computer network which includes an on-line account management system constructed in accordance with the teachings of the present invention. 
       FIG. 2  is an expanded block diagram of a mainframe computer system forming part of the computer network of  FIG. 1  and supporting the on-line account management system thereof. 
       FIG. 3  is an expanded block diagram of the on-line account management system of  FIG. 1 . 
       FIG. 4  is a flow chart illustrating a method of transporting billing information configured into a standardized format. 
       FIG. 5  is a flow chart illustrating a method of synchronizing account information maintained on-line with internally maintained account information. 
       FIG. 6  is an expanded block diagram of a first data space of the on-line account management system of  FIG. 3 . 
       FIG. 7   a  is a flow chart illustrating a method of archiving invoice information to and retrieving invoice information from an intermediate tier of the first data space of  FIG. 6 . 
       FIG. 7   b  is a flow chart illustrating a method of archiving invoice information to a lower tier of the first data space of  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a computer network  10  which includes an on-line account management system constructed in accordance with the teachings of the present invention. As disclosed herein, the computer network  10  is configured as a multi-tiered network which includes an unsecured network  12  within which a computer user operating a computer system  14  may freely operate, a limited access network  16 , protected from the unsecured network  12  by a first firewall  18 , which includes a computer system  20 , for example, a web server, containing information which the computer user may access if properly authorized but is otherwise inaccessible to unauthorized users within the unsecured computer network  12 , and a secured network  22 , protected from the limited access network  16  by a second firewall  24 , inaccessible to users operating within the unsecured network  12 . 
   In the example illustrated herein, the unsecured network  12  is the Internet, the limited access network  16  is an extranet and the secured network  22  is an intranet, for example, an enterprise network. It should be noted that, as illustrated herein, the extranet  16  includes computer systems, for example, the web server  20 , more commonly considered to form part of the Internet  12 . As used herein, however, a computer system configured to limit access to at least a portion of the content maintained thereby to authorized users is deemed to form part of an extranet operated by the content provider. Furthermore, it is fully contemplated that the invention disclosed herein is suitable for use within a wide variety of computer networks for which access to a first portion thereof is limited to a subset of the group of users having access to a second portion of the network. Thus, the invention is suitable for use within a wide variety of computer networks, including those fully or partially comprised of any combination of one or more local area networks (“LANs”), wide area networks (“WANs”), intranets, extranets and virtual private networks (“VPNs”). 
   In the embodiment of the invention disclosed herein, the extranet  16  and the enterprise network  22  are operated by a telecommunications service provider. It should be clearly understood, however, that the disclosure of the invention in connection with a telecommunications service provider is purely by way of example and that the extranet  16  and the enterprise network  22  may be operated by various types of business entities or other organizations which function as a provider of goods or services to others. In further accordance with the embodiment of the invention disclosed herein, the computer system  14  is operated by a customer with whom the telecommunications service provider will periodically conduct business transactions which are documented by one or more account records created and maintained by the telecommunications service provider. As will be more fully described below, in order to facilitate the ability of the customer to review and/or otherwise manage their account, the telecommunications service provider or other provider has provided certain account management functionality to the web server  20  where it is available to customers on-line over the Internet. As many of the account records to be made available to customers on-line are confidential, it is contemplated that those customers of the telecommunications service provider who wish to avail themselves of the available on-line account management services must first subscribe to those services. As a result, access to confidential account records may be limited to authorized individuals. Variously, it is contemplated that a customer may subscribe to the on-line account management services via a written request transmitted by hand or mail, a verbal request transmitted in person or telephonically or an electronic request transmitted via the Internet. Once a customer has subscribed to the on-line management services, the customer would be able to access various type of records related to an account or accounts that the customer maintains with the telecommunications service provider and/or otherwise manage their accounts in accordance with the techniques hereinbelow described. 
   The computer system  14 , for example, a personal computer (“PC”), is coupled to the unsecured computer network  12  by a communication link (not shown). Variously, the communication link may include an analog or digital dial-up connection, a digital subscriber line (“DSL”), a cable modem or a dedicated circuit. Of course, by way of example,  FIG. 1  shows a single PC  14  coupled to the unsecured computer network  12 . More typically, however, many more PCs (or other types of computer systems) would be coupled to the unsecured computer network  12 . A user accesses the unsecured computer network  12  using access software (not shown) residing on the PC  14 . For example, if the unsecured computer network  12  is the Internet or another computer network using the TCP/IP set of communication protocols, suitable access software would include a commercially available web browser, for example, Microsoft Explorer or Netscape Navigator. 
   Using the web browser, a user may view content maintained at a web server (not shown) located within the unsecured computer network  12  or, if desired, may view content maintained at the web server  20  located within the limited access network  16 . Typically, the web server  20  may have one or more mirrored servers (not shown), the number of which varies depending on the number and/or geographical distribution of users seeking to access the content identically maintained in both the web server  20  and the mirrored servers thereof. As disclosed herein, the web server  20  maintains two types of content unrestricted and restricted. Unrestricted content may be viewed by all users accessing the web server  20  while restricted content is limited to viewing by authenticated users who have been authorized to view the restricted content. Authentication is the process of verifying a user&#39;s identity while authorization is the process of restricting the resources that an individual can access after the authentication of the user has been accepted. To access content maintained at the web server  20 , a user operating the PC  14  would provide the browser with the universal resource locator (“URL”) address for the limited access network  16 . In turn, the browser would navigate to the limited access network  16  where a load balancer (not shown) would direct the browser to either the web server  20  (or a selected mirrored server thereof) where unrestricted content is downloaded to the browser for display, most typically, as a web page at the PC  14 . If the user operating the PC  14  later seeks to view restricted content, for example, if the user issues a request to the web server  20  to use an account management system  26  residing in the web server  20  to view invoice and/or A/R information, the user shall first be re-directed to a new location for initiation of authentication and/or authorization processes. 
   To perform the aforementioned authentication and/or authorization processes, the limited access network  16  further includes an access server  32 . The access server  32  has an access service (not shown) which interacts, in a manner to be more fully described below, with various computer systems forming part of the secured network  22 . While a single access server  32  is shown in  FIG. 1 , the number of access servers needed to support the web server  20  and the mirrored servers thereof will vary based upon a number of factors, among them, the number of web servers to be supported and the frequency at which the web servers require the services of an access server. Upon issuing a request to view restricted content, a second load balancer (also not shown) would select one of the access servers, for example, the access server  32 , to perform the authentication and/or authorization processes. The second load balancer would then re-direct the browser from the web server  20  to the access server  32 . 
   While a wide variety of authentication and/or authorization processes are known in the art and many such processes would be suitable for the disclosed purpose of restricting access to selected content to authenticated users who have been authorized to view that content, such authentication and/or authorization processes typically involve the user operating the PC  14  to provide the access server  32  with requested information, for example, an account number and a password. Upon receiving the requested information from the user, the access server  32  executes an authentication and/or authorization session using the access service to verify the user&#39;s identity and to determine whether the user is authorized to view the requested content. Of course, many authentication and/or authorization services are more sophisticated than the rudimentary session described herein. 
   As may be further seen in  FIG. 1 , the service provider providing content via the web server  20  uses a multi-tier authentication and/or authorization process in which a portion of the process is executed within the secured enterprise network  22  which, as previously set forth, is protected from access by third parties by the second firewall  24 . More specifically, when executing the authentication and/or authorization process, the access service residing on the access server  32  utilizes an authentication and authorization (“AAR”) service (not shown) residing on a registry server  36  and information stored on a registry database  40  to complete the authentication and/or authorization process. In addition to the AAR service, the registry server  36  also has a session management (“SM”) service (not shown) residing thereon. As will be more fully described below, the SM service works in conjunction with the AAR service during the authentication and/or authorization process. Again, it should be noted that, while  FIG. 1  shows a single registry server  36 , it is contemplated that the number of registry servers  36  needed to support the access server  32  and the mirrored servers thereof will vary based upon a number of factors, among them, the frequency at which the access service of the access server  32  and a runtime service (not shown) residing on the web server  20  require the services of the registry server  36 . Of course, it should be clearly understood that the foregoing description of the various services residing on the web server  20 , the access server  32  and the registry server  36  has been greatly simplified for ease of description and it is specifically contemplated that a number of other services which reside on the web server  20 , the access server  32  or the registry server  36  have been omitted for ease of description. 
   During the authentication and/or authorization process, a password and/or other information is provided to the access server  32  by a user of the computer system  14 . In turn, the provided information is transported by the access service of the access server  32  to a registry server, for example, the registry server  36 , selected by a third load balancer (not shown). The AAR service residing on the registry server  36  then checks the password and/or other information provided by the user against encrypted data stored in the registry database  40 . After the AAR service authenticates a user based upon a comparison of the password and/or other information provided by the user against encrypted data stored in the registry database  40  and determines a list of authorized privileges for the authenticated user, the AAR service will ask the SM service to assign a session ID and encryption key for the user. The SM service creates a new session and returns a session ID to the access service residing on the access server  32  which provided the information to the registry server  36 . To complete the login process, the access server  32  writes cookies back to the browser residing on the PC  14  that contains the session ID, user ID and encryption key. The browser is then redirected back to the web server  20  to continue the session. Now, however, the information contained in the cookies returned to the browser will enable the user to view the restricted content to which access had previously been sought. 
   Having been authorized to do so, the user may now use the account management system  26  residing in the web server  20  to perform a variety of tasks, for example, to view invoice and/or A/R information for their account. In accordance with the teachings of the present invention, various account management functionality has migrated from a mainframe system  38  forming part of the enterprise network  22  to the account management system  26  residing in the web server  20  forming part of the extranet  16 . By enabling the migration of the disclosed account management, functionality which heretofore was only accessible to users within the enterprise network  22 , for example, by a user of computer system  34 , may now be accessed by authorized users from the Internet  12 . While account management functionality has migrated from the mainframe system  38  to the account management system  26  residing in the web server  20 , the mainframe system  38  must still support the account management system  26 . 
   Referring next to  FIG. 2 , functionality within the mainframe system  38  which supports the account management system  26  will now be described in greater detail. As may now be seen, the mainframe system  38  is comprised of a processor subsystem  42  coupled to a memory subsystem  44 . As used herein, the term “processor subsystem” refers to the collective processing capacity of the mainframe system  38  and is intended to encompass both the central processing unit (“CPU”) as well as any other processing unit, for example, a coprocessor, residing within the mainframe system  38 . Similarly, the term “memory subsystem” refers to the collective memory capacity of the mainframe system  38  and is intended to encompass the main memory, auxiliary memory as well as any other memory unit residing within the mainframe system  38 . Of course, it should be clearly understood that the mainframe system  38  has been greatly simplified for ease of description and that numerous components thereof have been omitted from the drawing. 
   Residing in the processor subsystem  42  are a first (or “invoice processing”) application  46 , a second (or “web invoicing”) application  48 , a third (or “A/R data processing)” application  50  and a fourth application (or “A/R data synchronization”) application  52 . Each one of the applications  46  through  52  is a software application comprised of a series of instructions encoded in the memory subsystem  44  of the mainframe system  38  as computer readable program code and executable by the processor subsystem  42  of the mainframe system  38 . Of course, it should be clearly understood that many other applications typically reside in the mainframe system  38  and that these other applications have been omitted from  FIG. 2  for ease of description. The memory subsystem  44  is subdivided into plural data spaces, each of which maintains a different type of information. The spaces include a first data space  54  in which billing data records are maintained, a second data space  56  in which an extensible markup language format (or “XML-format”) billing information file is maintained, a third data space  58  in which a new account records data file is maintained, a fourth data space  60  in which a previous account records data file is maintained and a fifth data space  62  in which an updated account records data file is maintained. Of course, it should again be clearly understood that, in addition to the aforementioned data records and/or files, the memory subsystem  44  typically maintains a considerable amount of other data to support processing and/or data storage functionality other than the specific processing and/or data storage functionality disclosed herein. 
   Referring next to  FIG. 3 , functionality within the web server  20  which collectively forms the account management system  26  will now be described in greater detail. As may now be seen, the web server  20  is comprised of a processor subsystem  64  coupled to a memory subsystem  66 . Again, as used herein, the term “processor subsystem” refers to the collective processing capacity of the web server  20  and is intended to encompass both the central processing unit (“CPU”) as well as any other processing unit, for example, a coprocessor, residing within the web server  20 . Similarly, the term “memory subsystem” refers to the collective memory capacity of the web server  20  and is intended to encompass the main memory, auxiliary memory as well as any other memory unit residing within the web server  20 . Of course, it should be clearly understood that the web server  20  has been greatly simplified for ease of description and that numerous components thereof have been omitted from the drawing. 
   Residing in the processor subsystem  64  are a first (or “XML-format invoice generation”) application  68 , a second (or “A/R report generation”) application  70 , a third (or “archival and retrieval”) application  72  and a fourth (or “account management”) application  74 . Each one of the applications  68  through  74  is a software application comprised of a series of instructions encoded in the memory subsystem  66  of the web server  20  as computer readable program code and executable by the processor subsystem  64  of the web server  20 . Of course, it should be clearly understood that many other applications typically reside in the web server  20  and that these other applications have been omitted from  FIG. 3  for ease of description. The memory subsystem  66  is subdivided into plural data spaces, each of which maintains a different type of information. The plural data spaces include a first data space  76  in which subscriber invoices are maintained and a second data space  78  in which subscriber A/R reports are maintained. Of course, it should again be clearly understood that, in addition to the aforementioned subscriber invoices and subscriber A/R reports, the memory subsystem  66  typically maintains a considerable amount of other data to support processing and/or data storage functionality other than the specific processing and/or data storage functionality disclosed herein. 
   The first data space  76  in which subscriber invoices are maintained is a tiered memory subsystem which includes a first (or “upper”) tier  80 , a second (or “intermediate”) tier  82  and a third (or “lower”) tier  84 . As will be more fully described below, each tier  80 ,  82  and  84  maintains a respective subset of the set of invoices generated by the XML-format invoice generation application  68 . The upper tier  80  also maintains an index to the invoices maintained in the intermediate tier  82 . Invoices are written to the upper tier  80  by the XML-format invoice generation application  68 . Once written to the upper tier  80 , the invoices maintained thereat are accessible by the account management application  74  and the archival and retrieval application  72 . Invoices maintained in the intermediate tier  82 , however, may only be accessed by the archival and retrieval application  72 . The lower tier  84  of the tiered memory subsystem is not physically located within the memory subsystem  66  of the web server  20 . Rather, the lower tier  84  is a magnetic tape or other removable storage medium which may be temporarily coupled to the web server  20 , for example, by inserting the magnetic tape into a tape drive (not shown) forming part of the of the web server  20  and transferring invoices from the intermediate tier  82  onto the magnetic tape. Alternately, the lower tier  84  may be a remotely located device coupled to the web server  20  over a network. 
   Referring next to  FIG. 4 , a method of transporting billing information contained in the billing data records maintained in the data space  54  of the memory subsystem  44  of the mainframe system  38  to the account management system  26  residing in the web server  20  in a standardized format, for example, XML-format, suitable for viewing by a user of the computer system  14  over the Internet  12  will now be described in greater detail. Prior to commencing the method illustrated in  FIG. 4 , raw billing data for a provider of goods and/or services, for example, a telecommunications service provider, is input the invoice processing application  46 . Variously, the raw billing data may be retrieved from a raw billing data space (not shown) located within the memory subsystem  44  or transmitted to the invoice processing application  46  by the computer system  34  or other device (not shown) forming part of the enterprise network  22 . From the raw billing data received thereby, the invoice processing application  46  assembles plural billing data records for storage in the data space  54 . The invoice processing application also generates plural invoices in a fixed medium, typically, a print medium, for forwarding to customers, most commonly, by mailing paper copies of the printed invoices to the customers. 
   As disclosed herein, the billing data records contain account, product and usage information for each customer of the provider of goods and/or services. In addition to an alphanumeric code which uniquely identifies a customer, the account information for a customer may include information such as the customer&#39;s name and mailing address. Product information will identify those goods and/or services purchased by the customer. For example, if telecommunication services are being provided to a customer, the associated product information may include the calling plan or plans to which the customer has enrolled and the rate or rates at which the customer will be charged for various types of telephone calls made under the calling plan or plans. Usage information identifies each usage of the products or services purchased by the customer. For example, if a customer has subscribed to a calling plan offered by a telecommunications service provider, usage information may include each telephone number called by the customer. The usage information may also include the date, time and duration of each call made by the customer. Of course, it should be clearly understood that the billing data records need not necessarily include account, product and/or usage information for the customer. Rather, it is noted that the billing data records may include types of information other than those specifically recited herein. Furthermore, when the billing data records do include account, product and/or usage information, it should be clearly understood that the particular types of account, product and/or usage information disclosed herein may or may not be included as part of that information. Rather, it is fully contemplated that various types of account, product and/or usage information are entirely suitable for the purposes disclosed herein. 
   The method commences at step  86 . At step  86 , it is presumed that the web server  20  is powered up and accessible to computer users, for example, a user of the computer system  14  via the Internet  12 . It is further presumed that the account management application  74  and the XML-format invoice generation application  68  have been launched and are ready to begin executing operations. As previously described, at this step is the process, the third data space  54  of the memory subsystem  44  of the mainframe system  38  contains billing data records for plural customers of a provider of goods or services. As disclosed herein, the provider is a long distance telecommunications service provider and, as further disclosed herein, for each customer of the telecommunications service provider, the billing records contain account information which uniquely identifies the customer, product information which describes the various types of services purchased by the customer and usage information which details each usage of each service purchased by the customer. However, because this information is spread over multiple files and record types defined in accordance with a proprietary format, third parties lacking knowledge of the proprietary format would find it difficult to obtain the account, product and usage information for a customer from the billing data records maintained in the data space  54 . 
   From the start at step  86 , the method proceeds to step  88  where the web invoicing application  48  selects a first subscriber from a list of subscribers maintained in a sixth data space  55  of the memory subsystem  44  of the mainframe system  38 . As defined herein, a subscriber is a customer of the telecommunications service provider who has requested that selected account information, for example, invoice information and/or A/R information, be placed onto the web server  20  where it may be accessed, by the subscriber over the Internet  12 . Continuing on to step  90 , account, product and usage information for the selected subscriber is retrieved from the billing data records maintained in the first data space  54  by the web invoicing application  48  and, at step  92 , the retrieved account information is encoded into XML-format. Generally, XML is a technology where data elements are encased (or “wrapped”) in a document type definition (or “DTD”) which surrounds each data element. For example, if an account information data element indicates that the account number for a customer is 123456789, once encased, the corresponding account information data element would appear as follows: &lt;account-number&gt;123456789&lt;/account-number&gt;. Accordingly, at step  92 , each data element of the retrieved account information is encased in a DTD which describes that data element. The method then proceeds on to step  94  for determination if the information retrieved from the first data space  54  includes product information for the selected subscriber. If it is determined at step  94  that the retrieved information includes product information for the selected subscriber, the method proceeds to step  96  where a first product is selected from the retrieved product information. 
   Proceeding on to step  98 , the product information for the selected product is encoded into XML-format, again by encasing each data element thereof into a DTD which describes that data element. The XML-format product information for the selected product is then nested within the account information encoded into XML-format at step  92 . Continuing on to step  100 , the information retrieved from the first data space  54  is examined to determine if it includes usage information for the selected product. If so, the method proceeds to step  102  where a first usage of the selected product is selected and on to step  104  where the usage information for the selected usage is encoded into XML-format, again by encasing each data element thereof into a DTD which describes that data element. The XML-format product information for the selected usage is then nested within the product information encoded into XML-format at step  98 . 
   Continuing on to step  106 , the method examines the information retrieved from the first data space  54  to determine if the selected usage is the last usage for the selected product. If there are additional usages of the selected product contained in the information retrieved from the first data space  54 , the method proceeds to step  108  where a next usage of the selected product is selected. The method then returns to step  104  for further processing in the manner previously described. If, however, it is determined at step  106  that the selected usage is the last usage of the selected product or if it was determined at step  100  that the information retrieved from the first data space  54  does not contain any usage information for the selected product, the method will instead proceed to step  110  for further processing. 
   At step  110 , the information retrieved from the first data space  54  is again examined, this time to determine if the selected product is the last product for the selected subscriber. If it is determined that there are additional products for the selected subscriber, the method proceeds to step  112  where a next product is selected for the selected subscriber. The method would then return to step  98  for further processing in the manner previously described. If, however, it is determined at step  110  that the selected product is the last product for the selected subscriber or if was determined at step  94  that the information retrieved from the first data space  54  does not contain any product information for the selected subscriber, the method will instead proceed to step  114  for further processing. 
   At step  114 , the web invoicing application  48  will again examine the subscriber list maintained in the sixth data space  55  to determine if there are additional subscribers for which information needs to be retrieved from the first data space  54  is. If there are additional subscribers for which billing information should be retrieved from the first data space  54 , the method proceeds to step  116  where a next subscriber is selected. The method then returns to step  90  for further processing in the manner previously described. If, however, it is determined at step  114  that the selected subscriber is the last subscriber for which billing information was retrieved from the first data space  54 , the method will instead end at step  118 . 
   By executing the above-described method, a series of XML-format billing information files, each corresponding to a customer of the telecommunications service provider who has requested that invoice information for their accounts be available over the Internet  12 , are constructed. These billing information files are also termed as “integrated” billing information files since they not only contain plural types of invoice information but also a series of relationships between the plural types of invoice information contained therein. These relationships are created by wrapping data blocks within descriptions of the contents of the data blocks and nesting types of invoice information within other types of invoice information. For example, in the exemplary integrated billing information file reproduced below, not only can each call made under an “ANYTIME” calling plan be readily identified but specific items regarding each such call, for example, call duration, are equally identifiable. 
   Once constructed, the web invoicing application  48  stores the integrated XML-format billing information files in the second data space  56 . When ready for transfer to the XML-format invoice generation application  68  residing at the web server  20 , for example, when an integrated XML-format billing information file has been constructed for each customer who has subscribed to on-line billing information access, the web invoicing application  48  will compress the integrated XML-format billing information files, for example, using a conventional data compression algorithm, and subsequently transfer the compressed integrated XML-format billing information files to the XML-format invoice generation application  68  residing at the web server  20  using a conventional file transfer protocol (or “FTP”) process. For example, as an integrated XML-format billing information file is constructed for a selected subscriber, the web invoice application  48  may write the newly constructed integrated XML-format billing information file to the second data space  56 . A typical integrated XML-format billing information file containing wrapped usage information nested within wrapped product information nested within wrapped account information is configured as follows: 
                              &lt;account-block&gt;       &lt;account-number&gt;XXXXXXXXX&lt;/account-number&gt;       &lt;account-detail&gt;       &lt;charge-block&gt;       &lt;description&gt;       &lt;line&gt;SPRINT CHARGES&lt;/line&gt;       &lt;/description&gt;       &lt;charge-class&gt;       &lt;description&gt;       &lt;line&gt;AOL 5[ ANYTIME PROVIDED BY SPRINT&lt;/line&gt;       &lt;/description&gt;       &lt;charge-subclass&gt;       &lt;description&gt;       &lt;line&gt;State-to-State&lt;/line&gt;       &lt;/description&gt;       &lt;line-seq-nbr&gt;A&lt;/line-seq-nbr&gt;       &lt;calls&gt;000000002&lt;/calls&gt;       &lt;minutes&gt;00000000000400&lt;/minutes&gt;       &lt;amount&gt;0.20&lt;/amount&gt;       &lt;/charge-subclass&gt;       &lt;/charge-class&gt;       &lt;other-charge-class&gt;       &lt;description&gt;       &lt;line&gt;LONG DISTANCE MONTHLY CHARGES&lt;/line&gt;       &lt;/description&gt;       &lt;other-charge-subclass&gt;       &lt;description&gt;       &lt;line&gt;AOL/SPRINT LONG DISTANCE MONTHLY FEE&lt;/line&gt;       &lt;/description&gt;       &lt;line-seq-nbr&gt;J&lt;/line-seq-nbr&gt;       &lt;amount&gt;2.80&lt;/amount&gt;       &lt;/other-charge-subclass&gt;       &lt;/other-charge-class&gt;       &lt;/charge-block&gt;       &lt;tax-reg-block&gt;       &lt;description&gt;       &lt;line&gt;TAXES/REG. RELATED CHGS.&lt;/line&gt;       &lt;/description&gt;       &lt;tax-reg-class&gt;       &lt;description&gt;       &lt;line&gt;STATE SALES TAX&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.02&lt;/amount&gt;       &lt;/tax-reg-class&gt;       &lt;tax-reg-class&gt;       &lt;description&gt;       &lt;line&gt;STATE SALES TAX&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.22&lt;/amount&gt;       &lt;/tax-reg-class&gt;       &lt;tax-reg-class&gt;       &lt;description&gt;       &lt;line&gt;CARRIER UNIVERSAL SVC CHG&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.30&lt;/amount&gt;       &lt;/tax-reg-class&gt;       &lt;tax-reg-class&gt;       &lt;description&gt;       &lt;line&gt;CARRIER PROPERTY TAX&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.03 &lt;/amount&gt;       &lt;/tax-reg-class&gt;       &lt;tax-reg-class&gt;       &lt;description&gt;       &lt;line&gt;FEDERAL EXCISE TAX&lt;/Iine&gt;       &lt;/description&gt;       &lt;amount&gt;0.09&lt;/amount&gt;       &lt;/tax-reg-class&gt;       &lt;/tax-reg-block&gt;       &lt;/account-detail&gt;       &lt;itemization&gt;       &lt;itemization-calls&gt;       &lt;description&gt;       &lt;line&gt;ITEMIZATION OF CALLS&lt;/line&gt;       &lt;/description&gt;       &lt;footer2&gt;For a description of rate periods, please see terms and       conditions.&lt;/footer2&gt;       &lt;call-block&gt;       &lt;block-id&gt;1&lt;/block-id&gt;       &lt;orig-foncard&gt;       &lt;description&gt;       &lt;line&gt;ORIGINATING NUMBER:&lt;/line&gt;       &lt;/description&gt;       &lt;number&gt;XXXXXXXXXX&lt;/number&gt;       &lt;/orig-foncard&gt;       &lt;sery-block&gt;       &lt;call&gt;       &lt;call-id&gt;1&lt;/call-id&gt;       &lt;date&gt;       &lt;julian&gt;2002053&lt;/julian&gt;       &lt;display&gt;2/22/02&lt;/display&gt;       &lt;/date&gt;       &lt;time&gt;       &lt;hms&gt;1248390&lt;/hms&gt;       &lt;display&gt;12:48PM&lt;/display&gt;       &lt;/time&gt;       &lt;period&gt;D&lt;/period&gt;       &lt;location&gt;       &lt;city&gt;NEWORLEANS&lt;/city&gt;       &lt;state&gt;LA&lt;/state&gt;       &lt;/location&gt;       &lt;called-number&gt;XXXXXXXXXX&lt;/called-number&gt;       &lt;seconds&gt;00000000120&lt;/seconds&gt;       &lt;amount&gt;0.10&lt;/amount&gt;       &lt;taxes&gt;       &lt;fed-taxes&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/fed-taxes&gt;       &lt;surchg-taxes&gt;       &lt;amount&gt;0.01&lt;/amount&gt;       &lt;/surchg-taxes&gt;       &lt;state-taxes&gt;       &lt;amount&gt;0.01&lt;/amount&gt;       &lt;/state-taxes&gt;       &lt;total-taxes&gt;       &lt;amount&gt;0.02&lt;/amount&gt;       &lt;/total-taxes&gt;       &lt;/taxes&gt;       &lt;/call&gt;       &lt;call&gt;       &lt;call-id&gt;2&lt;/call-id&gt;       &lt;date&gt;       &lt;julian&gt;2002058&lt;/julian&gt;       &lt;display&gt;2/27/02&lt;/display&gt;       &lt;/date&gt;       &lt;time&gt;       &lt;hms&gt;1444000&lt;/hms&gt;       &lt;display&gt;2:44 PM&lt;/display&gt;       &lt;/time&gt;       &lt;period&gt;D&lt;/period&gt;       &lt;location&gt;       &lt;city&gt;NEWORLEANS&lt;/city&gt;       &lt;state&gt;LA&lt;/state&gt;       &lt;/location&gt;       &lt;called-number&gt;XXXXXXXXXX&lt;/called-number&gt;       &lt;seconds&gt;00000000120&lt;/seconds&gt;       &lt;amount&gt;0.10&lt;/amount&gt;       &lt;taxes&gt;       &lt;fed-taxes&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/fed-taxes&gt;       &lt;surchg-taxes&gt;       &lt;amount&gt;0.01&lt;/amount&gt;       &lt;/surchg-taxes&gt;       &lt;state-taxes&gt;       &lt;amount&gt;0.01&lt;/amount&gt;       &lt;/state-taxes&gt;       &lt;total-taxes&gt;       &lt;amount&gt;0.02&lt;/amount&gt;       &lt;/total-taxes&gt;       &lt;/taxes&gt;       &lt;/call&gt;       &lt;/serv-block&gt;       &lt;/call-block&gt;       &lt;/itemization-calls&gt;       &lt;/itemization&gt;       &lt;/account-block&gt;       &lt;hier-block&gt;       &lt;multiple-account-summary&gt;       &lt;description&gt;       &lt;line&gt;MULTIPLE ACCOUNT SUMMARY&lt;/line&gt;       &lt;/description&gt;       &lt;service-location&gt;       &lt;customer-name&gt;XXXX XXXXXXX&lt;/customer-name&gt;       &lt;description&gt;       &lt;line&gt;AOL 5[ANYTIME PROVIDED BY SPRINT]&lt;/line&gt;       &lt;/description&gt;       &lt;account-number&gt;XXXXXXXXX&lt;/account-number&gt;       &lt;standard-charges&gt;       &lt;amount&gt;3.00&lt;/amount&gt;       &lt;/standard-charges&gt;       &lt;discounts&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/discounts&gt;       &lt;taxes-reg-charges&gt;       &lt;amount&gt;0.66&lt;/amount&gt;       &lt;/taxes-reg-charges&gt;       &lt;total-charges&gt;       &lt;amount&gt;3.66&lt;/amount&gt;       &lt;/total-charges&gt;       &lt;/service-location&gt;       &lt;service-location&gt;       &lt;customer-name&gt;XXXX XXXXXXX&lt;/customer-name&gt;       &lt;description&gt;       &lt;line&gt;SPRINT FONCARD UPGRADE&lt;/line&gt;       &lt;/description&gt;       &lt;account-number&gt;XXXXXXXXX&lt;/account-number&gt;       &lt;standard-charges&gt;       &lt;amount&gt;0.47&lt;/amount&gt;       &lt;/standard-charges&gt;       &lt;discounts&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/discounts&gt;       &lt;taxes-reg-charges&gt;       &lt;amount&gt;0.12&lt;/amount&gt;       &lt;/taxes-reg-charges&gt;       &lt;total-charges&gt;       &lt;amount&gt;0.59&lt;/amount&gt;       &lt;/total-charges&gt;       &lt;/service-location&gt;       &lt;/multiple-account-summary&gt;       &lt;/hier-block&gt;       &lt;account-summary&gt;       &lt;summary-charges&gt;       &lt;description&gt;       &lt;line&gt;Summary of Charges&lt;/line&gt;       &lt;/description&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;Balance&lt;/line&gt;       &lt;line&gt;Forward&lt;/linc&gt;       &lt;/description&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/section-total&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;Account&lt;/line&gt;       &lt;line&gt;Adjustments&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.00&lt;/amount&gt;       &lt;/section-total&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;SPRINT&lt;/line&gt;       &lt;line&gt;Charges&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;3.47&lt;/amount&gt;       &lt;/section-total&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;Taxes and&lt;/line&gt;       &lt;line&gt;Regulatory&lt;/line&gt;       &lt;line&gt;Rel. Charges&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;0.78&lt;/amount&gt;       &lt;/section-total&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;Current&lt;/line&gt;       &lt;line&gt;Total&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;4.25&lt;/amount&gt;       &lt;/section-total&gt;       &lt;section-total&gt;       &lt;description&gt;       &lt;line&gt;Amount&lt;/line&gt;       &lt;line&gt;Due By&lt;/line&gt;       &lt;line&gt;3/23/02&lt;/line&gt;       &lt;/description&gt;       &lt;amount&gt;4.25&lt;/amount&gt;       &lt;/section-total&gt;       &lt;/summary-charges&gt;       &lt;/account-summary&gt;       &lt;puc-messages&gt;       &lt;message&gt;       &lt;description&gt;       &lt;line&gt;MESSAGE TO SPRINT/EARTHLINK CUSTOMERS&lt;/line&gt;       &lt;line&gt;$5.95 SAVINGS FOR EARTHLINK INTERNET AND SPRINT       LONG&lt;/line&gt;       &lt;line&gt;DISTANCE JOINT CUSTOMERS.&lt;/line&gt;       &lt;line&gt;FOR TAX APPLICATION AND REPORTING PURPOSES,       THE MONTHLY&lt;/line&gt;       &lt;line&gt;CHARGE HAS BEEN ALLOCATED AMONG IT&#39;S       APPLICABLE&lt;/line&gt;       &lt;line&gt;COMPONENTS (LONG DISTANCE AND INTERNET)&lt;/line&gt;       &lt;/description&gt;       &lt;/message&gt;       &lt;/puc-messages&gt;                    
It should be noted that, in the above-reproduced exemplary integrated XML-format billing information file, confidential information such as names, account numbers and telephone numbers have been masked from view.
 
   Once received at the web server  20 , the XML-format invoice generation application  68  constructs a series of XML-format invoices from the received integrated XML-format billing files by applying a template to the received integrated XML-format billing files. The XML-format invoice generation application  68  then writes the constructed XML-format invoices to the upper tier  80  of the first memory space  76  of the memory subsystem  66  of the web server  20  in a manner to be more fully described with respect to  FIG. 6 , below. 
   In the foregoing description, the web invoicing application  48  goes down the list of subscribers contained in the sixth data space  55 , selects, in sequence, each subscriber for which billing information has not yet been retrieved from the first data space  54 , retrieves account, product and usage information for the selected subscriber from the billing data records maintained in the first data space  54 , subsequently encodes the retrieved account, product and usage information therefore in a nested XML-format and writes the encoded account product and usage information to the second data space  56  as an integrated XML-format billing information file. Of course, it should be clearly understood that the foregoing process may be executed in a wide variety of manners. For example, after selecting a subscriber, the web invoicing application  48  may retrieve only the account information for the selected subscriber. After encoding the selected account information in XML-format, the web invoicing application  48  may then retrieve the product information for the selected subscriber from the first data space  54  for encoding into XML-format and subsequent nesting within the account information. Finally, the web invoicing application  48  may retrieve the usage information for the selected subscriber from the first data space  54 , again for encoding in XML-format and nesting within the product information. Alternately, the web invoicing application  48  may initially retrieve the usage information for the selected subscriber and subsequently retrieve the product information. The product information would then be used to encapsulate the usage information. Similarly, subsequently retrieved account information would be used to encapsulate the product information. 
   Like all customers, subscribers will periodically receive an invoice for services provided thereto by the telecommunications service provider in a non-electronic format, for example, a paper bill mailed to the subscriber. However, the subscriber may also view, over the Internet, a copy of that invoice in an electronic format. The subscriber may then choose to pay a selected one of the two copies of the invoice. 
   Referring next to  FIG. 5 , a method of synchronizing account information maintained on-line with internally maintained account information will now be described in greater detail. In the embodiment of the invention disclosed herein, A/R information maintained on a web server is synchronized with A/R information maintained on a mainframe system. It should be clearly understood, however, that the methods disclosed herein are equally suitable for synchronizing other types of information maintained on plural computer systems such that the information on each one of the plural computer systems is the same. Prior to commencement of the method, raw A/R data for a provider of goods and/or services, for example, a telecommunications service provider, is input the A/R data processing application  50 . Variously, the raw A/R data may be retrieved from a raw A/R data space (not shown) located within the memory subsystem  44  or transmitted to the A/R data processing application  50  by the computer system  34  or other device (not shown) forming part of the enterprise network  22 . From the raw A/R data received thereby, the A/R data processing application  50  assembles a current A/R data file containing a plurality of A/R reports, each identifying a customer of the provider of goods and/or services and a description of activity on an account assigned to that customer. Typically, activity on an account will include, among other items, a list of charges assessed to the account and payments made on the account. The A/R data processing application  50  will generate a series of customer A/R reports for use by the service provider. The A/R data processing application  50  will also store the current A/R data file in a seventh data space  57  of the memory subsystem  44 . 
   The method commences at step  120 . At step  120 , it is again presumed that the web server  20  is powered up and accessible to computer users, for example, a user of the computer system  14  via the Internet  12 . It is further presumed that the account management application  74  and the A/R report generation application  70  have been launched and are ready to begin executing operations. At step  122 , the A/R data processing application  50  passes the current A/R data file maintained in the seventh data space  57  to the A/R data synchronization application  52 . In turn, the A/R data synchronization application constructs a baseline account records data file from the received current A/R data file and the list of subscribers maintained in the sixth data space  55  of the memory subsystem  44  of the mainframe system  38 . As previously set forth, a subscriber is a customer of the telecommunications service provider who has requested that selected account information, for example, invoice information and/or A/R information, be placed onto the web server  20  where it may be accessed, by the subscriber over the Internet  12 . To construct the baseline account records data file, each A/R report in the current A/R data file which corresponds to a subscriber identified on the list of subscribers is added as an A/R report of the baseline account records data file. 
   After constructing the baseline account records data file, the method proceeds to step  124  where the A/R data synchronization application  52  writes the baseline account records data file to the third data space  58  in the memory subsystem  44  of the mainframe system  38  where it is maintained as a “new” account records data file containing a series of subscriber A/R reports. Continuing on to step  126 , the A/R data synchronization application  52  then transmits the baseline account records data file maintained in the third data space  58  of the memory subsystem  44  to the A/R report generation application  70  of the web server  20  using a conventional FTP process. In turn, the A/R report generation application  70  writes the received baseline account records data file to the second data storage space  78  of the memory subsystem  66  of the web server  20  where it is similarly maintained as a series of subscriber A/R reports. 
   In accordance with the teachings of the present invention, the A/R data synchronization application  52  residing at the mainframe system  38  and the A/R report generation application  70  residing at the web server  20  collectively operate to ensure that the subscriber A/R reports maintained in the third data space  58  of the memory subsystem  44  of the mainframe system  38  as the new account records data file match the subscriber A/R reports maintained in the second data storage space  78  of the memory subsystem  66  of the web server  20 . So long as the subscriber A/R reports maintained at the mainframe system  38  match the subscriber A/R reports maintained at the web server  20 , the mainframe system  38  and the web server  20  are said to be synchronized with one another. A loss of synchronization will occur, however, when the subscriber A/R reports maintained at the mainframe system  38  no longer match the subscriber A/R reports maintained at the web server  20 . Such a loss will occur whenever one or more of the subscriber A/R reports maintained at the mainframe system  38  changes relative to the subscriber A/R reports maintained at the web server  20 . 
   Proceeding on to step  128 , the method looks for the arrival of additional raw A/R data at the mainframe system  38 . Typically, additional raw A/R data will be periodically input the mainframe system  38 , for example, once every 24 hours. As before, the additional raw A/R data may be retrieved from a raw A/R data space (not shown) located within the memory subsystem  44  of the mainframe system  38  or transmitted to the A/R data processing application  50  by the computer system  34  or other device (not shown) forming part of the enterprise network  22 . The additional raw A/R data contains A/R information for each customer of the service provider for whom a new A/R-related transaction, for example, a payment on an account, was recorded during the subject time period. Upon receipt of the additional raw A/R data by the A/R data processing application  50  of the mainframe system  38 , the A/R data processing application  50  will construct an updated A/R data file from the current A/R data file maintained in the seventh data space  57  and the additional raw A/R data. The updated A/R data file will then be used to generate a new series of customer A/R reports, again for use by the service provider. The updated A/R data file will also be written to the seventh data space  57  of the memory subsystem  66  as the current A/R data file. 
   Similar to the current A/R data file generated by the A/R data processing application  50 , the updated A/R data file contains a plurality of A/R reports, each identifying a customer of the provider of goods and/or services and a description of activity on an account assigned to that customer. The updated A/R data file differs from the current A/R data file, however, in that it now reflects activity which occurred in the last 24 hours. Upon completing the construction thereof, the A/R data processing application  50  passes the updated A/R data file to the A/R data synchronization application  52 . In turn, the A/R data synchronization application  52  begins construction of an updated account records data file. To construct an updated account records data file, the A/R data synchronization application  52  must first construct a next “new” account records data file. 
   Proceeding on to step  130 , the A/R data synchronization application  52  constructs a next “new” account records data file. To do so, the A/R data synchronization application  52  again retrieves the subscriber list maintained in the sixth data space  55  of the memory subsystem  44  and constructs the next “new” account records data file using each A/R report in the updated A/R data file which corresponds to a subscriber identified on the list of subscribers. The method will then proceed to step  132  where A/R data synchronization application  52  transfers the “new” account records data file maintained in the third data space  58  to the fourth data space where it will be maintained as a “previous” account records data file. Continuing on to step  134 , the A/R data synchronization application  52  writes the next “new” account records data file to the third data space  58  where it will be maintained as the “new” account records data file. 
   At this point, the subscriber A/R reports maintained in the second data storage space  78  of the memory subsystem  66  of the web server  20  are no longer synchronized with the subscriber A/R reports contained in the “new” account records data file maintained in the third data space  58  of the memory subsystem  44  of the mainframe system  38 . However, as will be more fully described below, re-synchronization of the two may be established relatively quickly. 
   To re-synchronize the two, the method proceeds to step  136  where the A/R data synchronization application  52  constructs an “updated” account records data file comprised of the differences identified by comparing the “new” account records data file maintained in the third data space  58  to the “previous” account records data file maintained in the fourth data space  60 . Continuing on to step  138 , the constructed updated account records data file which contains the differences between the A/R reports contained in the “new” account records data file and the A/R reports contained in the “previous” account records is written to the fifth data space  62  as the “updated” account records data file. As the “updated” account records data file contains only those differences between the contents of the third data space  58  and the fourth data space  60 , the “updated” account records data file will typically be considerably smaller than either the “new” or “previous” account records data files. 
   The method then proceeds to step  140  where the A/R data synchronization application  52  transfers the “updated” account records data file to the A/R report generation application  70  using a conventional FTP process. As the “updated” account records data file contains only changes between the subscriber A/R reports contained in the “new” account records data file and the “previous” account records data file, the “updated” account records data file will generate much less traffic than when the baseline account records data file was transferred to the A/R report generation application  70  as part of step  126 . In turn, at step  142 , the A/R report generation application  70  updates the subscriber A/R reports maintained in the second data storage space  78  using the information contained in the received “updated” account records data file. By doing so, the A/R report generation application  70  has resynchronized the subscriber A/R reports maintained in the second data storage space  78  of the memory subsystem  66  of the web server  20  with the subscriber A/R reports maintained in the third data space  58  of the memory subsystem  44  of the mainframe system  38 . By maintaining synchronization of the subscriber A/R reports maintained in the second data storage space  78  of the memory subsystem  66  of the web server  20  with the subscriber A/R reports maintained in the third data space  58  of the memory subsystem  44  of the mainframe system  38 , when a customer who has subscribed, with the service provider, to view A/R information accesses A/R information for the account assigned to that subscriber using the account management application  74 , the customer will view A/R information which is identical to the A/R information maintained for that customer on the mainframe system  34 . 
   Continuing on to step  144 , the A/R data processing application  50  awaits the arrival of additional raw A/R data at the mainframe system  38 . If additional raw A/R data is received by the A/R data processing application  50  at step  144 , the method returns to step  130  for further processing in the manner previously described. If, however, no additional raw A/R data is received by the A/R data processing application  50 , the method ends at step  146 . 
   Referring next to  FIG. 6 , the upper tier  80  and the intermediate tier  82  of the first data space  76  will now be described in greater detail. As may now be seen, the upper tier  80  includes a first portion  148  which contains an on-line current invoice database and a second portion  150  which contains an on-line recent invoice index. The intermediate tier  82 , on the other hand, includes plural portions  152 - 1  through  152 - y , each of which contains an archived invoice file. As disclosed herein, the method of archiving and retrieving invoice information is configured such that first portion  148  of the upper tier  80  is to maintain three months of invoices (months “0” through “−2”), the intermediate tier  82  is to maintain nine months of invoices (months “−3” through “−11”) and invoices more than one year old are to be maintained by the third tier  82 . Of course, the foregoing periods of time for which invoices are to be maintained in the upper tier  80  and the intermediate tier  82  are purely exemplary and it is fully contemplated that any other suitable period may be selected instead. 
   As may be further seen in  FIG. 6 , the on-line current invoices maintained in the first portion  148  of the upper tier  80  are maintained in a database and arranged by subscriber, who, as previously set forth, is a customer of the service provider who has requested that their invoices be maintained on-line. Accordingly, the first portion  148  is sub-divided into plural entries  154 - 1  through  154 - x , each of which corresponds to one of the subscribers for whom invoices are maintained on-line. Depending on when the subscribers initially requested that their invoices be maintained on-line, each one of the plural entries  154 - 1  through  154 - x  may hold a different numbers of months of invoices for the corresponding subscriber. For example, entries  154 - 1  through  154 - 3  all hold invoices for four months (one of which is, as will be more fully described below, has been identified as an excessively aged invoice, archived in the archived invoice file  152  of the intermediate tier  82  and is awaiting deletion from the on-line current invoice database  148  of the upper tier  80 ) while the entry  154 - x  holds invoices for only two months. Such a result would occur if the subscriber “x” has only recently requested that their invoices be available on-line. 
   The on-line recent invoice index  150  is comprised of plural entries  156 - 1  through  156 - 7 , each of which corresponds to an invoice which has been removed from the on-line recent invoice database  148  of the upper tier  80  and archived in an available archived invoice file  152 - 1  through  152 - y  of the intermediate tier  82 . More specifically, each time that the archival and retrieval application  72  identifies an excessively aged invoice to be removed from the on-line current invoice database  148  of the upper tier  80 , the archival and retrieval application  72  creates an entry to be placed in the on-line recent invoice index  150 . As disclosed herein, each entry contains four fields. For example, the entry  156 - 1  includes a first field  156 - 1   a  which identifies the subscriber for whom an excessively aged invoice is being removed from the on-line current invoice database  148  of the upper tier  80  for storage in one of the archived invoice files  152 - 1  through  152 - y  of the intermediate tier  82 , a second field  156 - 1   b  which identifies the month of the invoice being archived, a third field  156 - 1   c  which identifies to which one of the archived invoice files  152 - 1  through  152 - y  that the invoice is being archived and a fourth field  156 - 1   d  which identifies the location, within that archived invoice file, of the invoice. For example, the entry  156 - 4  indicates that the invoice for month (−6) for subscriber  1  was archived in file  152 - 1  at offset A. To facilitate a determination as to which invoices have been archived for a particular subscriber, as disclosed herein, the entries  156 - 1  through  156 - 7  in the on-line recent invoice index  150  are arranged by subscriber. Thus, each time an entry is added to the on-line recent invoice index  150 , the location of any other entries, within the index  150 , for that subscriber is determined and the new entry added to the entries for that subscriber. Of course, to simplify construction of the index somewhat, the entries could be arranged in a chronological order corresponding to the order in which the excessively aged invoices were removed from the on-line current invoice database  148  of the upper tier  80  and archived in one of the archived invoice files  152 - 1  through  152 - y  of the intermediate tier  82 . 
   Finally, each one of the archived invoice files  152 - 1  through  152 - y  includes plural invoices each at a discrete location within the file. As illustrated in  FIG. 6 , the invoice for month (−6) for subscriber  1  is at a first location  158 - 1 , having an offset A, within the file  152 - 1 . Similarly the invoice for month (−5) for subscriber  1  is at a second location  158 - 2  having an offset B, the invoice for month (−4) for subscriber  1  is at a third location  158 - 3  having an offset C, the invoice for month (−4) for subscriber  2  is at a fourth location  158 - 4  having an offset D, the invoice for month (−3) for subscriber  1  is at a fifth location  158 - 5  having an offset E, the invoice for month (−3) for subscriber  2  is at a sixth location  158 - 6  having an offset F and the invoice for month (−3) for subscriber  3  is at a seventh location  158 - 7  having an offset G, all within the file  152 - 1 . As disclosed herein, each invoice is archived in the archived invoice file  152 - 1  of the intermediate tier  82  in the same order in which they were removed from the on-line current database  148  of the upper tier  80 . Thus, the invoice for month (−6) for subscriber  1  was the first invoice to be archived while the invoice for month (−3) for subscriber  3  is the most recent invoice to be archived. As the invoices are removed from the on-line current invoice database  148  of the upper tier  80 , the archival and retrieval application  72  adds the invoices to a selected archived invoice file, for example, the file  152 - 1 , until that file is filled. The archival and retrieval application  72  would then select a next archived invoice file, for example, the file  152 - 2 , for subsequent invoices selected for archival. 
   As illustrated in  FIG. 6 , the contents of the on-line current invoice database  148 , the on-line recent invoice index  150  and the archived invoice files  152 - 1  through  152 - y  resulted from a particular situation where, initially, only subscriber  1  had requested that their invoices be placed on-line. Thus, the invoices for months (−6) and (−5), invoices for only subscriber  1  were placed in the on-line current invoice database  148  by the XML-format invoice generation application  68 . At the same time, the archival and retrieval application  72  checked the contents of the on-line current invoice database  148  for excessively aged invoices. However, since all of the invoices maintained in the on-line current invoice database  148  were less than three months old, the archival and retrieval application  72  did not identify any excessively aged invoices requiring archival in the archived invoice files  152 - 1  through  152 - y . Subscriber  2  then requested that their invoices also be placed on-line. Accordingly, invoices for month (−4) were placed in the on-line current invoice database  148  for both subscribers  1  and  2 . Again, the archival and retrieval application  72  failed to identify any excessively aged invoices in the on-line current invoice database  148  requiring archival in the archived invoice files  152 - 1  through  152 - y . In the following month, subscriber  3  also requested that their invoices be place on line. Accordingly, invoices for month (−3) were placed in the on-line current invoice database  148  for subscribers  1 ,  2  and  3  by the XML-format invoice generation application  68 . During this pass, however, the archival and retrieval application  72  identified invoice (−6) for subscriber  1  as an excessively aged invoice, archived the identified invoice in the file  152 - 1  and added a corresponding entry to the on-line recent invoice index  150 . In the months that followed: invoices for month (−2) for subscribers  1 ,  2  and  3  were added to the on-line current invoice database  148  while invoice (−5) for subscriber  1  was removed from the on-line current invoice database  148 , archived in the file  152  and added as an entry in the on-line recent invoice index  150 ; invoices for month (−1) for subscribers  1 ,  2  and  3  were added to the on-line current invoice database  148 , invoices for month (−4) for subscribers  1  and  2  were removed from the on-line current invoice database  148 , archived in the file  152  and added as entries to the on-line recent invoice index  150 ; and invoices for month (0) for subscribers  1 ,  2  and  3  were added to the on-line current invoice database  148  while invoices for month (−3) were archived in the file  152  and added as entries to the on-line recent invoice index  150 . It should be noted, however, that  FIG. 6  is a “real-time” illustration of the contents of the upper and intermediate tiers  80  and  82  and that, having been archived in the file  152  and entered in the on-line recent invoice index  150 , the invoice for month (−3) for subscribers  1 ,  2  and  3  are, in  FIG. 6 , awaiting deletion from the on-line current invoice database  148 . 
   Referring next to  FIGS. 7   a - b , a method of archiving on-line account information in accordance with the teachings of the present invention will now be described in greater detail. More specifically, in  FIG. 7   a , a primary archival method is shown and, in  FIG. 7   b , a secondary archival method is shown. Turning first to  FIG. 7   a , the primary archival method commences at step  160 . At step  160 , it is again presumed that the web server  20  is powered up and accessible to computer users, for example, a user of the computer system  14  via the Internet  12 . It is further presumed that the archival and retrieval application  72  has been launched, configured and begun executing archival operations. Configuration information for the archival and retrieval application  72  may include the number of months of subscriber account information, for example, invoice information, that should be kept on-line, the size of each archive file to be filled with information removed from an on-line database, for example, the on-line current invoice database  148  which, as previously set forth, forms part of the upper tier  80  of the subscriber invoice data storage space  76 , what time of day the archival process should run and the day on which the archive process should run. For example, the archival and retrieval application  72  may be configured to: a) keep three months of subscriber invoices in the on-line current invoice database  148  forming part of the upper tier  80  of the subscriber invoice data storage space  76 ; b) construct 2 MB archived invoice files, for example, the files  152 - 1  through  152 - y ; and c) run the archival process at noon on every Sunday. As disclosed herein, the archival process will be described with respect to one particular type of subscriber account information in one specific location within one particular device, specifically, the information stored in the subscriber invoice data storage space  74  of the memory subsystem  66  of the web server  20 . It should be clearly understood, however, that, in further embodiments of the invention, the disclosed archival process may be applied to plural types of subscriber account information and/or plural data storage spaces of the memory subsystem  66 . In those embodiments of the invention, the information to be archived from the plural discrete data storage spaces may variously be archived in corresponding plural discrete archive files or in a common archive file. It should be further understood that the disclosed techniques have a wide variety of applications other than those specifically recited herein. 
   Once launched, the method proceeds to step  162  where the archival and retrieval application  72  will check to determine if it is time to conduct a check of the on-line current invoice database  148  of the upper tier  80  of the subscriber invoice data storage space  76 . If the archival and retrieval application  72  determines that the time of day and/or day of the week matches the time of day and/or day of the week at which the on-line current invoice database  148  is to be checked for excessively aged customer invoices, the method proceeds to step  152 . If, however, the archival and retrieval application  72  determines that the time of day and/or day of the week does not match the time of day and/or day of the week when the on-line current invoice database  148  of the upper tier  80  is to be checked for excessively aged invoices, the method returns to step  162  where the time of day and/or day of the week are again checked. While, as disclosed herein, the on-line current invoice database  148  is checked at noon on every Sunday, it should be clearly understood that it is fully contemplated that any desired time of day and day of the week may be selected. It is further contemplated that the frequency at which the on-line current invoice database  148  is checked may be varied from the weekly check disclosed herein. 
   If the archival and retrieval application  72  determines at step  162  that it is time to check the on-line current invoice database  148  of the upper tier for excessively aged invoices, the method proceeds to step  164  where the archival and retrieval application  72  selects a first subscriber for examination. Proceeding on to step  166 , the archival and retrieval application  72  determines the number of months of invoices which are maintained in the on-line current invoice database  148  for the selected subscriber. If it is determined at step  166  that the selected subscriber does not have an excess number of invoices, for example, three invoices, maintained in the on-line current invoice database  148 , the archival and retrieval application  72  concludes that the on-line current invoice database  148  does not have any excessively aged invoices for the selected subscriber account and the method proceeds to step  168  for determination if there are additional subscribers in the on-line current invoice database  148  that need to be checked for excessively aged invoices. If all of the subscriber accounts in the on-line current invoice database  148  have been checked for excessively aged invoices, the method proceeds to step  170  where the archival and retrieval application  72  determines that the archival process is complete. The method then returns to step  162  to await a next execution of the archival process. If, however, it is determined at step  168  that there are additional subscribers to be examined for excessively aged invoices, the method proceeds to step  172  for selection of a next subscriber for the on-line current invoice database  148 . The method then returns to step  162  for further processing of the newly selected subscriber in the manner previously described. 
   Returning now to step  166 , if it is determined that the on-line current invoice database  148  for the selected subscriber has one or more excessively aged invoices, the method will proceed to step  174  to begin the process of archiving the excessively aged invoices. At step  174 , a first excessively aged invoice for the selected subscriber is selected for examination. Proceeding on to step  176 , the archival and retrieval application  72  determines whether a flag of the selected invoice has been set. If the flag of the selected invoice has been set, the archival and retrieval application  72  determines that the entry is an excessively aged invoice which was previously restored to the on-line current invoice database  148  as part of a prior restoration of aged invoices to the subscriber&#39;s account information. If the flag is not set, however, the archival and retrieval application  72  determines that the selected entry is an excessively aged invoice which has remained in the on-line current invoice database  148  for an excessive period of time. 
   Accordingly, if the flag for the selected entry is set, the method proceeds to step  178  where the archival and retrieval application  72  determines if time has expired for the flagged entry. More specifically, an aged invoice is restored to the on-line current invoice database  148  for a specified period of time and, upon expiration of the specified period of time, the restored invoice will again be deleted from the on-line current invoice database  148 . The specified period of time is selected in order to enable the user requesting the restoration of the aged invoice sufficient time to print off or otherwise examine the aged invoice. For example, two weeks has proven suitable as the specified period of time. Variously, the specified time period may be selected during by a system administrator, for example, during the initial configuration of the archival/retrieval application  72  or may be selected by the user immediately prior to the restoration of the selected aged invoice. The specified period of time may also be tied to the charge associated with the restoration of the aged invoice to the on-line current invoice database  148 . For example, the service provider may charge the user a lower restoration fee if the restored invoice is to be kept on-line for only two weeks and a higher restoration fee if the restored invoice is to be kept on line for two months. 
   Returning to step  176 , if it is determined at step  176  that the selected aged invoice for the selected subscriber is not flagged or if it is determined at step  178  that time has expired for the flagged entry, the archival and retrieval application  72  concludes that the selected excessively aged invoice is to be deleted. Accordingly, the method proceeds to step  180  to begin deletion of the selected invoice. At step  180 , the archival and retrieval application  72  determines if there is enough space available in the archived invoice file currently being used for the archival of invoices, for example, in  FIG. 6 , the file  152 - 1  of the intermediate tier  82  of the subscriber invoice data storage space  76 , for the selected excessively aged invoice. If sufficient space for the selected excessively aged invoice is available in the current archived invoice file  152 - 1  of the intermediate tier  82 , the method proceeds to step  184  for further processing. If, however, it is determined at step  180  that there is not enough available space in the current archived invoice file  152 - 1  for the selected aged invoice, the archival and retrieval application  72  concludes that the current archived invoice file  152 - 1  of the intermediate tier  82  is filled. The method will then proceed to step  182  where a new current archived invoice file is created within the intermediate tier  82 , for example, in  FIG. 6 , the file  152 - 2 . The method will then proceed to step  184  for further processing. Of course, rather than creating a new file within the intermediate tier  82  only when the prior file is filled, in an alternate aspect of the invention, it is contemplated that plural files may be created initially for later filling with excessively aged invoices. 
   Having ensured that there is sufficient space in the current archived invoice file, for example, the file  156 - 1 , for the selected excessively aged invoice to be deleted from the on-line current invoice database  148 , at step  184 , the archival and retrieval application  72  generates a copy of the selected excessively aged invoice of the on-line current invoice database  148  of the upper tier  80 , compresses the copy of the excessively aged invoice and then writes the compressed copy of the selected excessively aged invoice to the current archived invoice file  156 - 1  of the intermediate tier. Continuing on to step  186 , an entry describing the selected excessively aged invoice which has now been compressed and copied into the current archived invoice file  156 - 1  is created and added to the on-line recent invoice index  150 . As previously set forth, the created entry includes a first field which holds a unique identifier of the subscriber, for example, the subscriber&#39;s name and/or account number, a second field which holds the month of the selected excessively aged invoice, a third field which identifies, within the intermediate tier  82  of the subscriber invoice data storage space  76 , the archived invoice file where the selected excessively aged invoice has been archived and a fourth field which identifies the specific location, within the temporary upper tier archive file, where the selected excessively aged invoice is maintained. After added an entry identifying selected excessively aged invoice and its location to the on-line recent invoice index  150 , the method proceeds to step  188  where the archival and retrieval application  72  deletes the selected excessively aged invoice from the selected subscriber account of the on-line current invoice database  148 . 
   Upon deleting the selected aged invoice from the selected subscriber account of the on-line current invoice database  148  at step  188  or upon determining that the time which a flagged restored invoice is to be maintained in the selected subscriber account of the on-line current invoice database  148  at step  178 , the method proceeds to step  190  where the archival and retrieval application  72  determines if the selected excessively aged invoice is the last excessively aged invoice for the selected subscriber. If it is determined at step  190  that there are additional excessively aged invoices for the selected subscriber to be examined for possible archival, the method proceeds to step  192  where the archival and retrieval application  72  selects a next excessively aged invoice for the selected subscriber account. The method then returns to step  176  for further processing in the manner previously described. 
   If, however, the archival and retrieval application  72  determines at step  190  that there are no further excessively aged invoices for the selected subscriber to be examined, the method will proceed to step  194  where the archival and retrieval application  72  determines if the selected subscriber account is the last subscriber account in the on-line current invoice database  148  in the upper tier  80  to be examined for excessively aged invoices. If the archival and retrieval application  72  determines that there are additional subscriber accounts to be examined, the method proceeds to step  196  for selection of a next subscriber account from the on-line current invoice database  148  of the upper tier  82  for examination. The method then returns to step  166  for further processing in the manner previously described. If, however, it is determined at step  194  that all of the invoices for subscribers for which invoices are maintained in the on-line current invoice database  148  have been examined for excessively aged invoices, the method will instead proceed to step  198  where the archival and retrieval application  72  determines that the archival process is complete. The method will then end at step  200 . 
   Of course, the primary archival process hereinabove described represents a single pass through the on-line current invoice database  148 . However, it should be clearly understood that, once launched, the archival and retrieval application  72  will repeatedly execute the archival process disclosed herein. The frequency at which the archival and retrieval application  72  will execute the archival process is controlled by a pre-selected time period designated during configuration of the archival and retrieval application  72 . Accordingly, unless the archival and retrieval application  72  is closed, upon completion of the archival process at step  200 , the method will return to step  160  to again execute the archival process in the manner previously described. 
   Unlike the archival process, the retrieval process is executed manually. As previously set forth, for any given subscriber, three months of invoices are maintained in the on-line current invoice database  148  of the upper tier  80  of the subscriber invoice data storage space  76  while compressed copies of an additional nine months of invoices are maintained in the archived invoice files  152 - 1  through  152 - y  maintained in the intermediate tier  80  of the subscriber invoice data storage space  76  and any earlier invoices are maintained in the lower tier  84  of the subscriber invoice data storage space. To view the invoices maintained in the upper tier  82 , a subscriber would initiate an access of those invoices over the Internet  12  via the account management application  74  of the web server  20 . If the subscriber wanted to view older invoices no longer maintained in the upper tier  84 , at the subscriber&#39;s request, the account management application  74  would issue a retrieval request to the archival and retrieval application  72  identifying the invoices to be retrieved. The account management application  74  would compare the invoices to be retrieved to those listed in the on-line recent invoice index  150 . If the requested invoices are listed in an entry of the on-line recent invoice index  150 , the archival and retrieval application  72  would retrieve the invoices from the intermediate tier  82  using the locational information contained in the entry, decompress the retrieved invoices and write the decompressed invoices to the upper tier  80 . The archival and retrieval application  72  would also set a flag on each retrieved invoice which controls the time which that invoice can remain in the upper tier  80 . The archival and retrieval application  72  would then notify the account management application  74  that the requested invoices were available on-line and the account management application  74  would notify the subscriber of the same. If, however, the requested invoices were not listed in the on-line recent invoice index  150 , the archival and retrieval application  72  would issue a request for manual retrieval of the invoice from the lower tier  84  of the subscriber invoice data storage space  76  and would notify the account management application of the expected delay in making the requested invoice available on-line. 
   Referring next to  FIG. 7   b , a secondary archival process in which invoices which have been deleted from the on-line current invoice database  148  of the upper tier  80  and archived in the archived invoice files  152 - 1  through  152 - y  of the intermediate tier are periodically selected for archival in the lower tier  84  will now be described in greater detail. Unlike the primary archival process which runs automatically once the archival and retrieval application  72  is launched, the secondary archival process must be run manually. The method commences at step  202  and, at step  204 , the method determines if it is time to run the secondary archival process. Any suitable period, for example, six months, may be selected as the frequency at which to run the secondary archival process. Upon reaching the appropriate time to run the secondary archival process, the method will proceed to step  206  where a first archived invoice file, for example, the archived invoice file  152 - 1 , is selected for further examination. At step  208 , a first invoice, for example, the invoice  158 - 1 , is selected from the selected archived invoice file for further examination. At step  210 , the method determines if the selected invoice is excessively aged. Of course, for purposes of the secondary archival process, an excessively aged invoice is one that has aged twelve months. 
   In accordance with the method, a count of the total number of invoices in the selected archived invoice file and the number of excessively aged invoices in the selected archived invoice file are maintained. Accordingly, at step  210 , the count of the total number of invoices in the selected archived invoice file is incremented by one and, if the selected invoice is determined to be excessively aged, the count of excessively aged invoices is also incremented by one. After incrementing one or both counts appropriately, the method proceeds to step  212  where it is determined if the selected invoice is the last invoice in the selected archived invoice file. If there are additional invoices in the selected archived invoice file to be examined, the method continues on to step  214  for selection of a next invoice and then returns to step  210  for further processing in the manner previously described. 
   If, however, it is determined at step  212  that all of the invoices in the selected archived invoice file have been examined, the method will instead proceed to step  216  where the total number of excessively aged invoices in the selected archived invoice file is compared to the total number of invoices in the selected archived invoice file. Continuing on to step  218 , if the total number of excessively aged invoices in the selected archived invoice file is determined to be equal to the total number of invoices in the selected archived file, the method classifies the selected archived invoice file as an excessively aged archived invoice file and the method will proceed to step  220  where a computer user will transfer the selected invoice archive file from the intermediate tier  82  to the lower tier  84  by conventional means. If, however, it is determined at step  218  that the number of excessively aged invoices in the selected archived invoice file is not equal to the total number of invoices in the selected archived file (typically, because the number of excessively aged invoices is less than the total number of invoices), the method determines that the selected archived invoice file has not become excessively aged and should not be transferred to the lower tier  84  of the subscriber invoice data storage space  76 . Accordingly, the method will instead proceed to step  222  where the selected archived invoice file will be kept in the intermediate tier  82 . Of course, rather than requiring a 1:1 ratio of the number of excessively aged archived invoices to match the number of archived invoices before selecting the archived invoice file for transfer to the lower tier  84 , it is fully contemplated that other ratios may be equally suitable for the purposes contemplated herein. For example, if 90% of the invoices archived in an archived invoice file are excessively aged, it may be suitable to transfer the archived invoice file to the lower tier  84 . 
   Continuing on to step  224 , it is determined if there are additional archived invoice files in the intermediate tier  84  to be examined for possible transfer to the lower tier  86 , the method proceeds to step  226  for selection of a next archived invoice file and then returns to step  208  for further processing in the manner previously described. If, however, it is determined at step  224  that all of the archived invoice files in the intermediate tier  84  have been examined, the method ends at step  228 . As before, however, the secondary archival process hereinabove described represents a single pass through the archived invoice files maintained in the intermediate tier  82  and, after completion of the secondary archival process at step  200 , the method will return to step  202  to again execute the secondary archival process in the manner previously described 
   Thus, there has been described and illustrated herein, a tiered storage system uniquely configured to periodically shift excessively aged invoices into an indexed lower tier, thereby maintaining subscriber access to larger amounts of invoice information without a corresponding consumption of additional memory resources. However, those skilled in the art should recognize that numerous modifications and variations may be made in the techniques disclosed herein without departing substantially from the spirit and scope of the invention. Accordingly, the scope of the invention should only be defined by the claims appended hereto.