6 Part 6: V-Modell Reference Activities

6.3 Activities

6.3.10 System Design

6.3.10.11 Developing Migration Concept

Purpose

When a migration will be planned, content, scheduling and organizational aspects shall be considered. It shall be defined in detail how the migration shall be carried out and which data and interfaces shall be migrated.

The framework conditions for the migration shall be identified, and the strategy for carrying it out shall be determined. Migration stages with activities that shall be carried out shall be planned, and it shall be determined how changes of the respective stage could be cancelled if required (rollback strategy).

The data flow shall be defined, and the condition of the data shall be examined. Depending on the results, the data transformation shall be defined. The migrated parts of the system will represent units of the system that shall be developed and will be integrated after the migration.

6.3.10.11.1 Specifying Migration Approach

When planning and carrying out a migration all essential framework conditions shall be taken into account. This will include for example the time window that will be available for a migration, the effects a failure of the migration would have on the business processes or the available personnel and the know-how.

Depending on the results, the strategy for carrying out the migration will be determined.

6.3.10.11.2 Defining Data Map

For the definition of the data map the »Data Model of the legacy system and the physical data model of the new system shall be compared. For each field the map will be defined in concrete terms. When doing this, for example the following aspects shall be considered:

• Will the structure of the legacy system be adopted and what will possibly have to be adapted?
• Which field of the old data model will be mapped on which field of the new data model and what will the map look like?
• On which data types will the data of the field mapped? Will it be necessary to carry out a type conversion?
• Which changes will have to be made on the data themselves?
• Will parts of the data will not be migrated?

The definition of the data map and the »Data Migration should be tool-based. Today a number of tools, for example in the field of data warehouses or provided by the databases themselves, that support this work suitably, are available.

6.3.10.11.3 Planning Migration

The execution of the migration shall be planned. The migration shall be planned in detail within the time window determined in the strategy, allowing sufficient time for a possible rollback of the changes.

For planning purposes the activities that shall be carried out will be identified and described, providing information about their duration and determining the responsible persons. The identified activities will be combined in stages that are determined by logical and time considerations.

The »Rollback Strategy will be planned analogously to migration planning. For the stages of migration planning all activities concerning the rollback of changes shall be scheduled, and for each stage the last possible time (from the time and content point of view) for performing a rollback shall be defined.