Risks in Rehosting or Rewriting Legacy Systems

This technical report discusses the risks associated with the rehost or rewrite approach to modernizing legacy systems, particularly in the context of insurance companies migrating away from mainframe systems. It outlines the increasing trend of such migrations due to the termination of mainframe support and rising maintenance costs. The report identifies common pitfalls encountered during these modernization projects, including inadequate preparation for architectural changes, insufficient consideration of data migration and linkages with peripheral systems, and lack of comprehensive QA testing. It emphasizes the importance of thorough analysis of existing systems before initiating modernization efforts. The report also details a structured approach for successful rehosting or rewriting, which includes delineating project scope, mapping overall architecture, and formulating a testing plan to ensure system quality. The document serves as a guide for organizations to avoid common mistakes and achieve successful modernization outcomes.