FACTOID # 12: It's not the government they hate: Washington DC has the highest number of hate crimes per capita in the US.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Legacy system

A legacy system is an existing computer system or application program which continues to be used because the user (typically an organization) does not want to replace or redesign it. Many people use this term to refer to "antiquated" systems. Image File history File links Please see the file description page for further information. ... Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer system. ... To meet Wikipedias quality standards, this article may require cleanup. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...


Legacy systems are considered to be potentially problematic by many software engineers (for example, see Bisbal et al., 1999) for several reasons. Legacy systems often run on obsolete (and usually slow) hardware, and sometimes spare parts for such computers become increasingly difficult to obtain. These systems are often hard to maintain, improve, and expand because there is a general lack of understanding of the system. The designers of the system may have left the organization, leaving no one left to explain how it works. Such a lack of understanding can be exacerbated by inadequate documentation or manuals getting lost over the years. Integration with newer systems may also be difficult because new software may use completely different technologies.


Despite these problems, organizations can have compelling reasons for keeping a legacy system, such as:

  • The costs of redesigning the system are prohibitive because it is large, monolithic, and/or complex.
  • The system requires close to 100% availability, so it cannot be taken out of service, and the cost of designing a new system with a similar availability level is high.
  • The way the system works is not well understood. Such a situation can occur when the designers of the system have left the organization, and the system has either not been fully documented or such documentation has been lost.
  • The user expects that the system can easily be replaced when this becomes necessary.
  • The system works satisfactorily, and the owner sees no reason for changing it – or in other words, re-learning a new system would have a prohibitive attendant cost in lost time and money.

If legacy software runs on only antiquated hardware, the cost of maintaining the system may eventually outweigh the cost of replacing both the software and hardware unless some form of emulation or backward compatibility allows the software to run on new hardware. However, many of these systems do still meet the basic needs of the organization. The systems to handle customers' accounts in banks are one example. Therefore the organization cannot afford to stop them and yet some cannot afford to update them. A monolithic architecture is where processing, data and the user interface all reside on the same system. ... In telecommunications and reliability theory, the term availability has the following meanings: 1. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. ... An emulator reproducing a console games playable atmosphere on a Windows computer. ... This article or section does not cite its references or sources. ... Banker redirects here; see wiktionary:banker for more meanings. ...


A demand of extremely high availability is commonly the case in computer reservation systems, air traffic control, energy distribution (power grids), nuclear power plants, military defense installations, and other systems critical to safety, security, traffic throughput, and/or economic profits. For example see the TOPS database system. A computer reservations system, or CRS, is a computerized system used to store and retrieve information and conduct transactions related to travel. ... Air Traffic Control Towers (ATCTs) at Amsterdams Schiphol Airport (Netherlands) Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. ... Transmission towers Transmission lines in Lund, Sweden Electric power transmission, or more accurately Electrical energy transmission, is the second process in the delivery of electricity to consumers. ... A nuclear power station. ... The Total Operations Processing System, better known by its initials TOPS, is a computer system for managing the locomotives and rolling stock (railroad cars) owned by a rail system. ...


The change being undertaken in some organizations is to switch to Automated Business Process (ABP) software which generates complete systems. These systems can then interface to the organizations' legacy systems and use them as data repositories. This approach can provide a number of significant benefits: the users are insulated from the inefficiencies of their legacy systems, and the changes can be incorporated quickly and easily in the ABP software. (At least, that's the intention.) Many computer systems are available in the commercial marketplace that address the various aspects of Business Process Management. ... A repository is a central place where data is stored and maintained. ...


Note that "legacy" has little to do with the size or even age of the system — mainframes run 64-bit Linux and Java, after all, right alongside 1960s vintage code. In fact, some of the thorniest legacy problems organizations now face are in trying to leverage or replace existing "fat client" Visual Basic code as customers demand reliable Web access.[citation needed] This article or section does not adequately cite its references or sources. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... Java is an object-oriented programming language developed by Sun Microsystems in the early 1990s. ... A fat client is a computer (client) in client-server architecture networks which typically provides rich functionality independently of the central server. ... Visual Basic (VB) is an event driven programming language and associated development environment from Microsoft for its COM programming model. ...

Contents

Legacy support

The term legacy support is often used with reference to obsolete or "legacy" computer hardware, whether peripherals or core components. Operating systems with "legacy support" can detect and use legacy hardware. A peripheral is a type of computer hardware that is added to a host computer in order to expand its abilities. ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ...


It is also used as a verb for what vendors do for products in legacy mode - they "support", or provide software maintenance, for obsolete or "legacy" products. In software engineering, software maintenance is the process of enhancing and optimizing deployed software (software release), as well as remedying defects. ...


In some cases, "legacy mode" refers more specifically to backward compatibility. This article or section does not cite its references or sources. ...


The computer mainframe era saw many applications running in legacy mode. In the modern business computing environment, n-tier, or 3-tier architectures are more difficult to place into legacy mode as they include many components making up a single system. Government regulatory changes must also be considered in a system running in legacy mode. This article or section does not adequately cite its references or sources. ... In computing, Three-tier is a client-server architecture in which the user interface, functional process logic (business rules) and data storage and data access are developed and maintained as independent modules, most often on separate platforms. ... In computing, Three-tier is a client-server architecture in which the user interface, functional process logic (business rules) and data storage and data access are developed and maintained as independent modules, most often on separate platforms. ... This article is about the built environment. ...


Virtualization technology allows for a resurgence of modern software applications entering legacy mode. As system complexity and software costs increase, many computing users are keeping their current systems permanently in legacy mode. In computing, virtualization is a broad term that refers to the abstraction of computer resources. ... Application software is a subclass of computer software that employs the capabilities of a computer directly to a task that the user wishes to perform. ...


Alternative view

There is an alternate point of view — growing since the "Dot Com" bubble burst in 1999 — that legacy systems are simply (and only) computer systems that are both installed and working. In other words, the term is not at all pejorative — quite the opposite. Perhaps the term "legacy" is only an effort by computer industry salesmen to generate artificial churn in order to encourage purchase of unneeded technology. 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... Churn is a river that runs through Gloucestershire. ...


IT analysts estimate that the cost to replace business logic is about five times that of reuse, and that's not counting the risks involved in wholesale replacement. Shareholders and managers are increasingly asking, "Why are we spending so much money on new technology with so little to show for it?" Ideally businesses would never have to rewrite most core business logic. After all, debits must equal credits — they always have, and they always will. Businesses and governments are also recoiling at well-publicized system failures and security breaches that all too commonly arrive with new software — failures which are utterly catastrophic in many cases. (A regional airline fired its CEO due to the failure of a relatively new crew scheduling system during Christmas, 2004, for example.[1]) There's also a growing backlash against large, packaged software products (SAP, Oracle, PeopleSoft, and others) which were oversold and in some cases have proven too costly, inflexible, and poorly matched to business needs. Regional airlines are a type of airline service that is intended to feed a larger airline or larger aircraft. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... SAP AG (ISIN: DE0007164600, FWB: SAP, NYSE: SAP) is the largest European software enterprise, with headquarters in Walldorf, Germany. ... Oracle Corporation (NASDAQ: ORCL) is one of the major companies developing database management systems (DBMS), tools for database development, middle-tier software (Fusion Middleware), enterprise resource planning software (ERP), customer relationship management software (CRM) and supply chain planning (SCM) software. ... PeopleSoft, Inc. ...


Increasingly the IT industry is responding to these understandable business concerns. "Legacy modernization" and "legacy transformation" are now popular terms, and they mean reusing and refactoring existing, core business logic by providing new user interfaces (typically Web interfaces) and service-enabled access (e.g., through Web services). These techniques allow organizations to understand their existing code assets (using discovery tools), provide new user and application interfaces to existing code, improve workflow, contain costs, minimize risk, and enjoy classic qualities of service (near 100% uptime, security, scalability, etc.).[citation needed] Technology companies involved in "enterprise transformation" are growing and profiting by what many people feel is a more rational approach toward legacy systems.[citation needed] A web service is a collection of protocols and standards used for exchanging data between applications. ...


The reexamination of attitudes toward legacy systems is also inviting more reflection on what makes legacy systems as durable as they are. Technologists are relearning the fact that sound architecture, practiced up front, helps businesses avoid costly and risky rewrites in the first place. The most common legacy systems tend to be those which embraced well-known IT architectural principles, with careful planning and strict methodology during implementation. Poorly designed systems often don't last. Thus, many organizations are rediscovering not only the value in the legacy systems themselves but also their philosophical underpinnings. A typical vision of a computer architecture as a series of abstraction layers: hardware, firmware, assembler, kernel, operating system and applications (see also Tanenbaum 79). ...


References

    • "Failure of a relatively new crew scheduling system during Christmas" by Stephanie Overby, CIO Magazine, May 1, 2005
    • Bisbal, J., Lawless, D., Wu, B. & Grimson, J. (1999). Legacy Information System Migration: A Brief Review of Problems, Solutions and Research Issues. IEEE Software, 16, 103-111.

    Further reading

    • Jim McGee. "Legacy Systems: Why History Matters", Enterprise Systems Journal, 2005-11-10.

    2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... November 10 is the 314th day of the year (315th in leap years) in the Gregorian Calendar, with 51 days remaining. ...

    See also

    This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer system. ... In computing, a legacy encoding is a character encoding that cant represent all of Unicode, but is still used for compatibility or other reasons. ... A legacy port is a port or connector on a PC that is considered fully or partially obsolete. ... In engineering and computing, a stovepipe system is a legacy system that is an assemblage of inter-related elements that are so tightly bound together that the individual elements cannot be differentiated, upgraded or refactored. ... Software brittleness is the ironic term that describes the increasing difficulty of fixing older software. ... Data migration is the transferring of data between storage types, formats, or computer systems. ... The Free On-line Dictionary of Computing (FOLDOC) is an online, searchable encyclopedic dictionary of computing subjects. ... GNU logo (similar in appearance to a gnu) The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free content, designed by the Free Software Foundation (FSF) for the GNU project. ...


      Results from FactBites:
     
    Legacy system - Wikipedia, the free encyclopedia (1015 words)
    A legacy system is an existing computer system or application program which continues to be used because the user (typically an organization) does not want to replace or redesign it.
    Legacy systems are considered to be potentially problematic by many software engineers (for example, see Bisbal et al., 1999) for several reasons.
    The system requires close to 100% availability, so it cannot be taken out of service, and the cost of designing a new system with a similar availability level are high.
      More results at FactBites »

     
     

    COMMENTARY     


    Share your thoughts, questions and commentary here
    Your name
    Your comments

    Want to know more?
    Search encyclopedia, statistics and forums:

     


    Press Releases |  Feeds | Contact
    The Wikipedia article included on this page is licensed under the GFDL.
    Images may be subject to relevant owners' copyright.
    All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
    Usage implies agreement with terms, 1022, m