Hi
I really have to advise against the upgrade. GMS 5.7 is tested and supported only on MS SQL 2005 and 2008. It will never be tested on other versions.
What this means in practice is that we cannot guarantee the functionality on those platforms. Consequently if you run into problems, we won't be able to support you. You're better off keeping an isolated system with current MS SQL 2008 in one corner of your server room.
Database compatibility is listed in the 6.3 & 6.4 Admin guide page 10:
"The Guest Management Software has been tested with the following third-party database engines:
• PostGRE SQL 8.3.7 (Linux). This is the recommended external database.
• Microsoft SQL Server 2005 or 2008 (Windows).
• Oracle XE 10.2.0.1-1.0 (Linux).
• MySQL Standard 5.0.51 (Linux)."
Since the latest version isn't supported on >2008, it's easy to see the older ones aren't either.