Only databases created in 4D versions 6.0, 6.5, 6.7, 6.8, 2003, and 2004 can be converted to 4D v11 SQL. Databases created in previous versions will need to be converted to at least 4D 6.5. Note that a license is not needed to convert. For example you could download and use 4th Dimension 2004 to convert a 4D 3.5 database. Just run 4D in "demo" mode in order to complete the conversion.

Beyond that, follow these tips when preparing for any conversion:

• Backup – Make a full backup of the database. This could be a 4D backup or a “custom” backup (e.g. archiving the database in a zip file). The important thing is to have a functional backup.
• 4D Tools maintenance – You need to make sure that the database and data file are okay. Converting damaged files might be hazardous. Check the database with the compatible version of 4D Tools. Compact your database. However, never compact a damaged database.
• Uninstall components – “Former mode” components must be uninstalled with the appropriate version of 4D Insider prior to conversion to 4D v11 SQL.
• Check plug-in compatibility – Replace all 4D plug-ins with their 4D v11 SQL counterparts. For third-party plug-ins make sure that they are compatible with 4D v11 SQL. Ask for Universal Binary plug-ins from third parties (Mac OS).
• Make sure you have sufficient hard drive space! – The 4D v11 SQL conversion process automatically makes a copy of any modified files (including the structure and data files) so be sure to have sufficient disk space for the copies.
• Does the database contain data from other languages? (See below)