Legacy Systems - Revision history

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-A '''legacy system''', in the context of computing, refers to outdated computer systems, programming languages or application software that are used instead of available upgraded versions. Legacy systems also may be associated with terminology or processes that are no longer applicable to current contexts or content, thus creating confusion. In theory, it would be great to be able to have immediate access to use the most advanced technology. But in reality, most organizations have legacy systems - to some extent. A legacy system may be problematic, due to compatibility issues, obsoletion or lack of security support. A legacy system is also known as a legacy platform.<ref>Definition - What does Legacy System Mean? [https://www.techopedia.com/definition/635/legacy-system Techopedia]</ref>
+A '''legacy system''', in the context of [[Computing System|computing]], refers to outdated [[Computer|computer systems]], [[Programming Language|programming languages]] or [[Application|application]] [[Software|software]] that are used instead of available upgraded versions. Legacy systems also may be associated with terminology or processes that are no longer applicable to current contexts or content, thus creating confusion. In theory, it would be great to be able to have immediate access to use the most advanced technology. But in reality, most organizations have legacy systems - to some extent. A legacy system may be problematic, due to compatibility issues, obsoletion or lack of security support. A legacy system is also known as a legacy platform.<ref>Definition - What does Legacy System Mean? [https://www.techopedia.com/definition/635/legacy-system Techopedia]</ref>
-Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System?  [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>
+Gartner defines legacy system as, "An [[Information System (IS)|information system]] that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the [[Information System (IS)|information systems (IS)]] professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System?  [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>
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 == Legacy System Structures<ref>Legacy System Structures [https://ifs.host.cs.st-andrews.ac.uk/Resources/Notes/Evolution/LegacySys.pdf University of St. Andrews]</ref> ==
-Legacy systems are not simply old software systems although the software components of these systems are the main focus in this section. Legacy systems are socio-technical computer-based systems (so they include software, hardware, data and business processes). Changes to one part of the system inevitably involve further changes to other components. Decisions about these systems are not always governed by objective engineering criteria but are affected by broader organizational strategies and politics.
+Legacy systems are not simply old software systems although the software components of these systems are the main focus in this section. Legacy systems are socio-technical computer-based systems (so they include [[Software|software]], [[Hardware|hardware]], [[Data|data]] and [[Business Process|business processes]]). Changes to one part of the system inevitably involve further changes to other components. Decisions about these systems are not always governed by objective engineering criteria but are affected by broader [[Business Strategy|organizational strategies]] and politics.
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 Figure 1. illustrates the different logical parts of a legacy system and their relationships:
-#System hardware In many cases, legacy systems have been written for mainframe hardware which is no longer available, which is expensive to maintain and which may not be compatible with current organizational IT purchasing policies.
+#System hardware: In many cases, legacy systems have been written for mainframe hardware which is no longer available, which is expensive to maintain and which may not be compatible with current organizational IT purchasing policies.
 #Support software The legacy system may rely on a range of different support software from the operating system and utilities provided by the hardware manufacturer through to the compilers used for system development. Again, these may be obsolete and no longer supported by their original providers.
-#Application software As I discuss later, the application system which provides the business services is usually composed of a number of separate programs which have been developed at different times. Sometime the term legacy system means this application software system rather than the entire system.
+#Application software: The application system which provides the business services is usually composed of a number of separate programs which have been developed at different times. Sometime the term legacy system means this application software system rather than the entire system.
-#Application data These are the data which are processed by the application system. In many legacy systems, an immense volume of data has accumulated over the lifetime of the system. This data may be inconsistent and may be duplicated in different files.
+#Application data: These are the data which are processed by the application system. In many legacy systems, an immense volume of data has accumulated over the lifetime of the system. This data may be inconsistent and may be duplicated in different files.
-#Business processes These are processes which are used in the business to achieve some business objective. An example of a business process in an insurance company would be issuing an insurance policy; in a manufacturing company, a business process would be accepting an order for products and setting up the associated manufacturing process.
+#Business processes: These are processes which are used in the business to achieve some business objective. An example of a business process in an insurance company would be issuing an insurance policy; in a manufacturing company, a business process would be accepting an order for products and setting up the associated manufacturing process.
-#Business policies and rules These are definitions of how the business should be carried out and constraints on the business. Use of the legacy application system may be embedded in these policies and rules.
+#Business policies: and rules These are definitions of how the business should be carried out and constraints on the business. Use of the legacy application system may be embedded in these policies and rules.
 [[File:socio-technical system.png|300px|Layered Model of Legacy System]]

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	*Performance and productivity. Legacy systems become slower and slower over time, which means performance, efficiency and productivity can also decrease.		*Performance and productivity. Legacy systems become slower and slower over time, which means performance, efficiency and productivity can also decrease.
	*Maintenance costs and competitiveness. Maintaining a legacy system means investing money on an IT resource that will need to be replaced sooner or later.		*Maintenance costs and competitiveness. Maintaining a legacy system means investing money on an IT resource that will need to be replaced sooner or later.
		+
		+
		+	== See Also ==
		+	*[[Application Modernization]]
		+	*[[Application Modernization Services]]
		+	*[[Mainframe]]
		+	*[[Maintenance Repair and Operations (MRO)]]
		+	*[[Data Migration]]
		+
		+
		+	== References ==
		+	<references/>

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 *Knowledge and Training: As technologies change, new resources hired often lack knowledge of how legacy software solutions work. While some training can be provided, the impact can become quite severe as time progresses.
-[[File:Lifecycle Span Legacy System.jpg|300px|Lifecycle Span Legacy System]]
+[[File:Lifecycle Span Legacy System.jpg|400px|Lifecycle Span Legacy System]]
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 *Validating the data to make sure the move goes as planned. Once data is extracted, transformed, and cleaned, a sample set of data is imported to test for problems and errors. This weeds out potential issues before the new system goes live.
 *Loading the data into the new system. The final step to a successful data migration is loading all the data into the new system so it is ready for use.

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	*Compatibility with new systems and the possibility of adding more functions - since legacy systems are limited in their functionality and can’t be developed further.		*Compatibility with new systems and the possibility of adding more functions - since legacy systems are limited in their functionality and can’t be developed further.
	Once you identify a legacy system, it’s time to decide whether it’s worth replacing it. The process will certainly be time-consuming, but keep in mind that legacy software should be replaced at some point. Especially if it doesn’t meet your needs and is not secure anymore, as it may be using old security protocols and standards. Still, one of the most important factors will most likely be the cost of upgrading the outdated technology, as well the time required for the whole process. Evaluate both of them carefully, and trust a specialist to carry out a proper analysis for your organization. Only then you can make an informed choice about the future of a legacy system.		Once you identify a legacy system, it’s time to decide whether it’s worth replacing it. The process will certainly be time-consuming, but keep in mind that legacy software should be replaced at some point. Especially if it doesn’t meet your needs and is not secure anymore, as it may be using old security protocols and standards. Still, one of the most important factors will most likely be the cost of upgrading the outdated technology, as well the time required for the whole process. Evaluate both of them carefully, and trust a specialist to carry out a proper analysis for your organization. Only then you can make an informed choice about the future of a legacy system.
		+
		+
		+	== Legacy System Types<ref>Legacy System Types [https://nix-united.com/blog/what-is-a-legacy-system-and-legacy-software/#legacy_types Nix]</ref> ==
		+	When considering legacy systems, there are five different types of issues or problems that companies can encounter.
		+	*End of Life: Perhaps the most common legacy system type, end of life (EOL) legacy systems are everywhere. The reason for EOL systems is actually fairly simple. Vendors and Developers are businesses too. They also need to stay current with the latest technology. This often means that systems designed with older legacy software fall out of support as the resources and knowledge are either lost or become too expensive to maintain. With EOL legacy systems, vendors stop offering updates and discontinue selling the product.
		+	*No Updates: With an EOL legacy system, the vendor might offer to upgrade you to a new solution that offers similar functionality. If this option is not available, however, businesses are stuck. In the case where no updates are available, businesses need to consider alternatives whether that is a new software solution or a new provider, or both.
		+	*Scalability: Legacy systems and legacy software were designed at a time where specific infrastructure was available. As such newer technologies – for example, AI, the cloud, and big data – are things they are unable to support. In this case, the legacy solution will not be able to grow with the business and a new alternative will need to be explored.
		+	*Patches: Security patches are critical for many systems, however as time progresses, older legacy systems become more and more vulnerable. If the original developer has stopped supporting the product (EOL) then the risk can become critical.
		+	*Knowledge and Training: As technologies change, new resources hired often lack knowledge of how legacy software solutions work. While some training can be provided, the impact can become quite severe as time progresses.
		+
		+	[[File:Lifecycle Span Legacy System.jpg\|300px\|Lifecycle Span Legacy System]]

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	Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System? [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>		Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System? [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>
		+
		+
		+	__TOC__


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	An alternative way of looking at these different components of a legacy system is as series of layers as shown in Figure 2. Each layer depends on the layer immediately below it and interfaces with that layer. If interfaces are maintained, then it should be possible to make changes within a layer without affecting either of the adjacent layers.		An alternative way of looking at these different components of a legacy system is as series of layers as shown in Figure 2. Each layer depends on the layer immediately below it and interfaces with that layer. If interfaces are maintained, then it should be possible to make changes within a layer without affecting either of the adjacent layers.
		+
		+
		+	== Identifying Legacy Systems<ref>What should you focus on when trying to identify if a legacy system is in use at a business? [https://freeportmetrics.com/blog/what-is-a-legacy-system-and-why-do-companies-keep-using-them/ Freeport Metrics]</ref> ==
		+	*The year of creation or implementation, as most legacy systems are outdated and advanced in age.
		+	*Current performance - legacy systems are often associated with poor efficiency and lower productivity.
		+	*The availability of software updates and vendor support (or lack thereof, to be precise).
		+	*Compatibility with new systems and the possibility of adding more functions - since legacy systems are limited in their functionality and can’t be developed further.
		+	Once you identify a legacy system, it’s time to decide whether it’s worth replacing it. The process will certainly be time-consuming, but keep in mind that legacy software should be replaced at some point. Especially if it doesn’t meet your needs and is not secure anymore, as it may be using old security protocols and standards. Still, one of the most important factors will most likely be the cost of upgrading the outdated technology, as well the time required for the whole process. Evaluate both of them carefully, and trust a specialist to carry out a proper analysis for your organization. Only then you can make an informed choice about the future of a legacy system.

← Older revision		Revision as of 22:01, 30 November 2021
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	Legacy systems are not simply old software systems although the software components of these systems are the main focus in this section. Legacy systems are socio-technical computer-based systems (so they include software, hardware, data and business processes). Changes to one part of the system inevitably involve further changes to other components. Decisions about these systems are not always governed by objective engineering criteria but are affected by broader organizational strategies and politics.		Legacy systems are not simply old software systems although the software components of these systems are the main focus in this section. Legacy systems are socio-technical computer-based systems (so they include software, hardware, data and business processes). Changes to one part of the system inevitably involve further changes to other components. Decisions about these systems are not always governed by objective engineering criteria but are affected by broader organizational strategies and politics.

		+
		+	[[File:Legacy System Components.png\|400px\|Legacy System Components]]

← Older revision		Revision as of 21:45, 30 November 2021
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	Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System? [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>		Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System? [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>
		+
		+
		+	== Legacy System Structures ==
		+	Legacy systems are not simply old software systems although the software components of these systems are the main focus in this section. Legacy systems are socio-technical computer-based systems (so they include software, hardware, data and business processes). Changes to one part of the system inevitably involve further changes to other components. Decisions about these systems are not always governed by objective engineering criteria but are affected by broader organizational strategies and politics.
		+
		+
		+
		+	Figure 1. illustrates the different logical parts of a legacy system and their relationships:
		+	#System hardware In many cases, legacy systems have been written for mainframe hardware which is no longer available, which is expensive to maintain and which may not be compatible with current organizational IT purchasing policies.
		+	#Support software The legacy system may rely on a range of different support software from the operating system and utilities provided by the hardware manufacturer through to the compilers used for system development. Again, these may be obsolete and no longer supported by their original providers.
		+	#Application software As I discuss later, the application system which provides the business services is usually composed of a number of separate programs which have been developed at different times. Sometime the term legacy system means this application software system rather than the entire system.
		+	#Application data These are the data which are processed by the application system. In many legacy systems, an immense volume of data has accumulated over the lifetime of the system. This data may be inconsistent and may be duplicated in different files.
		+	#Business processes These are processes which are used in the business to achieve some business objective. An example of a business process in an insurance company would be issuing an insurance policy; in a manufacturing company, a business process would be accepting an order for products and setting up the associated manufacturing process.
		+	#Business policies and rules These are definitions of how the business should be carried out and constraints on the business. Use of the legacy application system may be embedded in these policies and rules.
		+
		+	An alternative way of looking at these different components of a legacy system is as series of layers as shown in Figure 2. Each layer depends on the layer immediately below it and interfaces with that layer. If interfaces are maintained, then it should be possible to make changes within a layer without affecting either of the adjacent layers.

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 Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."<ref>What is a Legacy System?  [https://www.gartner.com/en/information-technology/glossary/legacy-application-or-system Gartner]</ref>
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 *Budgetary constraints often lead corporations to not address the need of replacement or migration of a legacy system. However, companies often don't consider the increasing supportability costs (people, software and hardware, all mentioned above) and do not take into consideration the enormous loss of capability or business continuity if the legacy system were to fail. Once these considerations are well understood, then based on the proven ROI of a new, more secure, updated technology stack platform is not as costly as the alternative—and the budget is found.
 *Due to the fact that most legacy programmers are entering retirement age and the number of young engineers replacing them is very small, there is an alarming shortage of available workforce. This in turn results in difficulty in maintaining legacy systems, as well as an increase in costs of procuring experienced programmers.