Chapter 3. Migration strategy and planning 33
򐂰 Development environment
This group includes tools and frameworks used to develop your applications’
code. Here is where the greater portion of the technical migration will be
done, and this migration can be done in different ways as discussed in 3.1.3,
“Strategies to handle migration complexity” on page 33. It is recommended
that you have software version control and backup copies of your work as you
progress through the project.
򐂰 Test environments
Every test environment is included in this group: system test, performance
test, pre-production, etc. Some of them should be as close as possible to the
production environment configuration in order to obtain more realistic results,
especially if you are focused on performance. Generally, these test
environments are developed initially for deploying and testing the application
being developed, but the same environments can be used to test the
application migration.
򐂰 Production environment
The production environment is where the applications are actually running.
This is the most sensitive environment since migration will have a direct
impact on your business. The magnitude of this impact will depend on the
migration approach you decide to use. This decision will be based on several
factors, such as hardware availability and business requirements, among
others. Refer to 3.5, “Migrating the site” on page 58 for further details about
the migration approaches.
Identify one development team and assign it the task of migrating one simple
application. This task should not be complicated, but it will give the team a feel
for the new platform, the differences with the previous one, as well as hands-on
experience; this will also give you a measure of the time needed to migrate.
Consider that not all the development teams are the same; the applications could
be very different (not only in size, but in complexity) and they may have different
delivery schedules, so, in turn, you might have to plan to migrate the applications
at different times, having both application servers running concurrently and
interoperating for a period of time. The issues of interoperability are covered in
“Vertical slice strategy” on page 35.
3.1.3 Strategies to handle migration complexity
Once you have the first application ready to migrate, you have to decide on a
migration strategy. Based on the belief that a small problem is easier to solve
than a large one, we discuss three different methods to achieve this strategy. In
some cases, you will need to apply more than one method to get to the most
atomic form of the problem. These migration strategies are:

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