How can we Keep our sales history and customer information on website while Upgrading magento version. There is ongoing sales and customer information in Production website.
usually we can keep the part of the database that is not being upgraded, so we don’t overwrite those tables. i.e. Sales and Customer.
I am using Magento version on production is CE 2.1.7
IS there any way I can separate or configure those database table?
Any help will be great to me.
I don't think there's a way around this really. The upgrade may need to make changes to those tables (it won't delete data but an upgrade may need to alter the structure of those tables). Even if no changes are being made to those tables, code is being updated so it's not save for customers or administrators to have access to the website at the same time in case they experience inconsistencies or create integrity constraint violations.
Here's a guide on the the best way to upgrade from command line: http://devdocs.magento.com/guides/v2.2/comp-mgr/cli/cli-upgrade.html