there is no direct 15 - 17 upgrade, you have to do it in versions
15 - 16 then 16 - 17.
how ever, if you do not have the same modules that you have in 15 installed in 17, you will have nothing but problems and tons of errors.
here is a read on it along with links to the db upgrade
Hello , i am using odoo community 15 for a while , and right now i have interest to use Odoo 17 community edition all my module is standart , that come with odoo community 15 , no custom module i try to restore odoo 15 backup database on odoo 17 , and did not work are there any guide to do it ...
www.odoo.com
upgrade.odoo.com