Legacy Information Systems
Priyadarshi Tripathy, Kshirasagar Naik · 2014
This chapter identifies the problem an organization faces in dealing with legacy information systems (LISs). It discusses six viable solutions to the problem: freeze, outsourcing, carry on maintenance, discard and redevelop, wrap, and migrate. Wrapping is a straightforward way to modify and enhance a legacy component. The chapter explains four categories of wrappers that include: database wrappers, system service wrappers, application wrappers and function wrappers. Upon the completion of the job, the wrapper takes over the output files to be forwarded to the client. Migration comprises three main steps: (i) conversion of the existing schema to a target schema; (ii) conversion of data; and (iii) conversion of program. The chapter explains seven approaches to migration that include: Cold turkey, Database first, Database last, Composite database, Chicken little, and Butterfly Iterative.