Is it possible to keep the data created by a feature after deleting feature itself?
I created a migration feature that is really just a one off; I would want to delete it without losing the nodes created from it.
Features module is a way to export most of the settings normally stored in the database into code. If you delete the feature, you delete the code which deletes everything.
The cool thing about features is you can change the settings for things (views, panels, etc) at any time and those changes get stored in the database. Once they're stored in the database it should be OK to delete the feature (though I haven't tried this myself).
The easiest way to do this would be to go into each item that your feature has and re-save it. For example, if your feature had a view called "News" you can go to Structure > Views > News > Edit. Then click save on that view. If you look at your feature, it should now say "Overridden."
Once everything is overridden, it should be OK to delete the feature. Make sure you do a backup of everything and try disabling the feature first to make sure everything you need doesn't disappear.
You can use the Features Tools module. The main goal of the module is to give the ability to remove elements from a feature and put them back to the DB.