Chapter 15. Code and Data Migration

with Santiago Comella-Dorda

Santiago Comella-Dorda is a business analyst with McKinsey & Company.

Give me where to stand, and I will move the earth.

”Archimedes, Mathematical Collection ,
book VIII, proposition 10, section 11,
Pappus of Alexandria (date unknown)
translated into Latin (1588)

As noted at the end of Chapter 13, RSS stakeholders selected an architectural transformation strategy that dictated that code be migrated in the first phase, followed by the database in a second phase. Parallel operations would not be used. In Chapter 14, we selected a system preparation strategy that migrates data from DMS to Oracle without major changes to the schema and retargets the legacy COBOL code to the Solaris platform. The next step is to develop plans for code migration and data migration.

The code migration plan is a refinement of the first phase of the architectural transformation strategy and identifies which program elements are modernized in each increment. Unless objective criteria are devised, the code migration plan will be driven by external forces or by chance. The criteria for assigning program elements to increments are derived from the overall modernization goals. We established the following criteria for the RSS modernization effort.

• Minimize the number of adapters. Reducing the need for adapters should reduce overall development costs for the system.

• Migrate program elements with related functionality at the same time. Reducing the number of adapters as the only criterion may not result in an optimal migration plan because program elements with widely varying functionality will be migrated together. This lack of focus makes it difficult to comprehend and implement system requirements.

• Map increment size to the funding profile. Effort must be mapped to available funding. Project funding may be constant, ramp up steadily and then ramp down, or vary, based on spending projections.

Although it is not performed until after the code migration, data migration must be planned so that the cost of the overall modernization strategy can be estimated.