>Hi
>
>I use with VFP8.
>
>It's native step to upgrade to VFP9, but I afraid obout errors (code,data, any other), especially something that invisiable problem that I can discover too late.
>
>I will appriciate information that will cover all potential risks and resolving/ignoring (as set enginbehivr) options.
>
>It is very critical step for me.
>I heard about 'No pain no gain' but I want to know the pain potential.
>
>
>Big thanks


I would not go quite so far as "painless" but it shouldn't be bad. Have a look at the book "What's New in Visual FoxPro 9" -- Naomi posted a link to it. It's a pretty fast read. The change in behavior of GROUP BY clauses in SQL Select statements, mentioned by Dmitry, is probably the biggest issue you will run into. This isn't completely recommended but if time is of the essence you can get around that by issuing SET ENGINEBEHAVIOR 70 in your main program.

If I were you I would back up everything, open the project in VFP 9, build it, and see what happens. That way it's easy to back out if you don't like the outcome.