I'm open to learning new things, but I gotta tell ya', I'm struggling with this one!  Could someone please explain the system architecture to me in a way that I can be convinced to give up my old-school paradigm?  I have always made changes in one instance (DEV) and then, after unit testing, migrated my changes to a pristine copy of production (TST) where integration testing was performed. If the changes passed QA/UAT in TST, then they were migrated to production (PRD).

We branched off from PRD more than a month ago into what is being called "TST". Our current environment no longer resembles PRD because we have been experimenting as we try to find solutions.  Odoo suggests that we transport directly from TST to PRD.

1.  The processes are not working in TST due to a configuration error that nobody wants to find or fix.  Bottom line: it doesn't work.

2.  The changes have not ever been tested in an environment that looks like PRD.  I don't know if it will work there or not.

Please help a sister out!  Are you guys using a 2- or 3-tier system?  What have you seen to be the advantages and/or disadvantages of your approach?