Newer versions of LabKey require more recent versions of PostgreSQL; for example, current LabKey Server releases don't support PostgreSQL 8.3 or earlier, since the PostgreSQL team no longer supports these old releasses. LabKey will refuse to start if it's pointed at an unsupported database version. Supported versions of external components are detailed here: https://www.labkey.org/wiki/home/Documentation/page.view?name=supported

LabKey Server automatically performs schema upgrades when you upgrade LabKey Server itself, but it performs no operations when you upgrade your database version. Instead, our database dialect layer automatically detects the current database version and runs the code most appropriate to that database version.

Our recommendation in general would be to upgrade your database version first, make sure that works correctly, and then upgrade LabKey version. Separating the steps will help isolate the cause of any problems, although it might not be possible in all scenarios.

I hope this helps...

Adam