I have one Developer Portal in Bluemix API Connect for the Development environment, one for Testing environment and one for Production environment. I have made some customizations in the structure of the modules, settings and content and I would like to migrate them from one environment to the other.
I have a theme for the styles, fonts and images but there are settings and content that are not included in the theme. I have found some Drupal plugins to migrate tables from the database. However, there is a risk of overwriting tables related with the API, products, plans, etc.
I would like to know if there is a recommended way of doing this migration without having to do everything again manually.
There isn't currently a simple way to migrate that sort of configuration between portal sites. There is a Drupal module called "Features" which can export / import capability but it doesn't support all configuration and isn't a process we have tested or documented, so you'd be using it at your own risk. You presumably uploaded your custom theme to one site, so you can just upload it again to the second site - that bit is simple.
If its an extensive amount of configuration then you can raise a support ticket and ask Ops to overwrite the target site with the configuration of the previous site - but that's a one off process, it would completely wipe the target site. So that isn't really going to help with ongoing changes.
You can write a custom drupal module to make your configuration changes - then simply load the module on each site and it would make the desired changes. However that can be a lot of work. If you only have a couple of sites it's likely easier to simply redo the same changes manually.
Hopefully this will improve in the future.
(Full Disclosure: I am part of the API Connect development team)