Importing Organization and User Mapping issue

Hello,

I am upgrading CRM 2013 On-premise to CRM 2015 On-premise.

PS:  Both the servers are in different Domain.

Step 1 : I have done CRM 2013 Organization Database backup and Restore it to CRM 2015 SQL Server.

Step 2 : Run Deployment Manager to import Organization

Step 3 : Selected Database, given Org name, Report Server url

Step 4 : On User mapping screen, I have checked Auto option.

Step 5 : It has mapped some users which are present in Target Server Domain.

PS: Rest users which are not mapped, are having CRM Records in CRM 2013.

In case, I proceed with the same scenario,

1. What will happen with CRM records whose owning users are not mapped? Will this records be seen in CRM 2015? Who will be the owner of them?

2. Will I be able to locate these records later on and map them with correct user anyway?

Please suggest.

Thank you