http://www.hcltech.com/search/apachesolr_search/custom-application-services ~More on Custom Application Services
Legacy applications usually exist within an ecosystem of interfaces, tools and utilities on the mainframe which they actively interact with. Legacy applications, in general, also do not exist on the mainframe in isolation and as such share certain application assets and the mainframe resources with other applications. The presence of such interactions and dependencies makes it imperative that any rehosting exercise focuses on not just the application inventory but also on providing a similar eco-system on the target platform for the application to run in.