Hello Dave,
The user will be able to login to a company where his/her Person record is set up. This is how it works. This is a basic set up.
Global Users are a way of making things easier for these users who need to work in multiple companies. With a Global User record it is not needed anymore to create Person records in each company and have separate passwords in each company. Global user record will work like a Global Person record - with one Person record only and one password only for all the companies assigned.
What should not happen - user with a Person record and no Global User record able to log in to a company where his/her Person record does not exist.
My advice is - create Global users for those who should have access to more than one company. And assign only those companies on Global User record. You can create Global Users records to users working in one company only - if you assume sooner or later they might need access to other companies as well. But this is not needed, the Person record will work just fine.
HansaWorld Support Team