When you convert a database to 4D v11 SQL any modified files are copied to a folder called "Replaced Files (Conversion)". This will include items like the structure file and data file (including segments).

This brings up some important points:

• Make sure you have sufficient hard drive space for a complete copy of the structure and data file. These files will be duplicated as part of the conversion process.
• Be sure that you have a functional backup of the database prior to conversion. The files in the "Replaced Files" folder are not a complete backup of the database. I.e. if you try to launch the structure file from the "Replaced Files" folder in 4D it will fail. These files are a "fail safe", in case the conversion fails, but it is still important to have a true backup as well.