When not to migrate
Before migrating any data, ensure you have taken the following into consideration:
Should your data be migrated? (Do you fit one of the use cases above?)
Is it worth retaining the data in the old instance?
Are your back-ends compatible? (Is it possible to migrate your data from one environment to another?)
Do you have custom code?
A clean install can avoid the problems of unwanted or obsolete data being transferred from the old instance, and prevent any unexpected results in the conversion process. Obvious configuration items like target systems, templates, roles, and so on are easily observable and can be duplicated in the new instance. Implementing a new version without carrying forward the old version’s configuration provides a good opportunity to leverage new features and re-engineer components in a better way.
If the old instance contains unique data such as profile attributes that cannot be constructed from target system lists, security question data from user registrations, password reset history, or product usage statistics in the session log, then that can strengthen the argument for mass migration of the old instance. However, pinpoint migration of only the unique data is possible and should also be considered.