Legacy system

System Fundamentals

In computing, a legacy system is an old method, technology, computer system, or application program, "of, relating to, or being a previous or outdated computer system."Often a pejorative term, referencing a system as "legacy" often implies that the system is out of date or in need of replacement.

Legacy systems are usually still in use as opposed to retired (or archived) systems, which are no longer in use. Please remember this distinction.

All about legacy systems

Systems must be compatible with other systems if they are going to be useful. Legacy systems are not always compatible with newer systems. Compatibility is a state in which two things are able to exist or occur together without problems or conflict. When you are planning a new system, you should be aware of compatibility issues with older systems. Frequently, the way a legacy system stores data is the most frequent source of compatibility issues. Please also understand the range of possible problems legacy systems can have:

1. Maintaining old systems often includes old application programs
2. Legacy systems can be hard to understand and expensive to change because programs might be disorganized
3. Documentation might be missing
4. Poor maintenance might introduce security problems
5. It may be difficult to find people who have the knowledge and skills to work with old systems
6. Legacy system are typically quite large and complex

A few hypothetical examples may help you understand this:

1. A new system accepts input for a date as 11 November 2017, but the legacy system only accept input as 11 November 17
2. A new system is web-based, but an older system is not web-based
3. A new system allows UTF-8 (Unicode Transformation Format-8) characters but the legacy system does not.
4. A new system assumes all currencies are in US dollars, while the legacy system does not.
5. A new system stores time as HH:MM:SS:MS (HH: hour, MM: minute, SS: second, MS: millisecond) but the legacy system stores time as HH:MM:SS.
6. A new system assumes all numbers can have 4 decimal places, while a legacy system assumes all numbers only have 2 decimal places.
7. A new system stores data in XML while a legacy system stores data in plain text.

Real-world practical advice

When you are planning a new system you should include compatibility planning as part of your new system. If you are a system administrator, programmer, network administrator, much of your work will involve getting different systems to be compatible. It's always nice when you have a new system, new company, and a new process, but this isn't the norm.

There is a lot more to say about this, but my advice is to assume any system you are involved with needs to be compatible with other systems and legacy systems.

Standards

• Outline compatibility issues resulting from situations including legacy systems or business mergers.

A state in which two things are able to exist or occur together without problems or conflict.

A state in which two things are able to exist or occur together without problems or conflict.

Give a specific name, value or other brief answer without explanation or calculation.

A state in which two things are able to exist or occur together without problems or conflict.

a group or system of interconnected people or things.

Give a brief account.