Legacy Systems Migration: A Method and its Tool-Kit Framework

The problems posed by mission-critical legacy systems - brittleness, inflexibility, isolation, non-extensibility, lack of openness etc. - are well known, but practical solutions have been slow to emerge. Most approaches are "ad hoc" and tailored to peculiarities of individual systems. This paper presents an approach to mission-critical legacy system migration : the Butterfly Methodology, its data migration engine and supporting tool-kit framework. Data migration is the primary focus of the Butterfly methodology, however, it is placed in the overall context of a complete legacy system migration. The fundamental premise of the Butterfly methodology is to question the need for parallel operation of the legacy and target systems during migration. Much of the complexity of the current migration methodologies is eliminated by removing this interoperation assumption.