17.6 Costing the Final Database Migration

RSS data conversion involves three types of work: creating a new database schema, migrating the data, and converting the new system to use the newly structured data. When creating a new database schema, data fields in the old database are reallocated to new tables and rearranged. New fields may be created by either combining or splitting old fields. Data migration includes effort spent in mapping from one structure to the other, creating scripts to migrate the data, testing the scripts, and transferring the data from the old database to the new one. Finally, as explained in Section 15.4, the entity beans representing the data persistence layer have to be modified to use the new database structure and revalidated.

Costing for this type of work takes the lower path shown in Figure 17-1. The work is broken down into detailed tasks . Using engineering judgment, an estimate of the effort and time each task could take is used to build up a cost and duration.

Unfortunately, there usually is little data to support this kind of planning. The remedy is to collect data as soon as possible by closely monitoring the initial execution of data conversion tasks and then check the engineering-judgment figures. This bootstrap method means that the initial estimate will probably be low and that an updated estimate of cost and duration should be expected. Managing these risks is critical if the organization lacks a productivity factor for this type of work. One risk mitigation activity is to pilot an effort to collect the needed data to refine the initial estimate.