The new Sedna Upsizing Wizard can handle the data migration for you. It has an engine that can be driven by your app. No UI needed.

>Thanks for all the replies to my post, all the comments have been very helpful in giving us the 50,000ft view on what needs to happen. The One thing I forgot to mention is that the application is vertical market, in hundreds of sites worldwide. The development challenges of converting it to SQL remain, but we also need to build good tools to reliably migrate existing users.
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>We're talking to some people who've done this before to get a feel for the scope of work to convert our application, and we'll go from there.
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>Thanks again,
>Chris