Full disclosure: I am an Epicor employee working within Support and am very biased towards solutions that take Support out of the equation. Any time someone doesn’t need to call in Support, that’s a win win for everyone. Migrations have many points where problems could present…UOM, codepages, UD fields, data corruption that could need to be addressed at V904 (in the middle of the process), different data fixes that need to be run at a different point, whether or not you need historical financial data (the ol’ 10080 conversion), etc.
Talk to your CAM about using Epicor Cloud services to complete an V803 to E10.2.200.x migration using our Cloud infrastructure. It is priced as a loss leader and we basically give the service away. That team automatically addresses whatever data related issues that could appear as part of the service so you don’t have to worry about it. Performance is much better than anything one could do on premise including upload / download time of the database to/from our Cloud storage location. Anything they do to address issues like data corruption/etc in the first pass migration get automatically applied every other pass without human intervention.
There is also the ERP Analyzer which is part of this offering (though, one can use it without a formal engagement to use the migration service) which allows you to see the modifications made to your system (BAQs, dashboards, BPMs, custom reports, etc), data distribution, and a lot of other detail. If nothing else, call your CAM(salesperson) and ask them to enroll you so you can use the ERP Analyzer which is free to use, to get an idea of how much work may be needed to uplift the modifications.
That said, I have an earlier post where I mention the process if one wanted to do this in-house. Just substitute references to 10.1.500 with the current release, which as of today is 10.2.200.