Doing a post-mortem on a CUCM migration gone bad....
Customer was running CUCM 6.1.3 and wanted to go to 7.0.2. The partner knew that this was not a supported upgrade path, but this was prior to 7.1 FCS and the customer was eager to move forward (and didn't care about losing 6.1.3 specific features). CUCM 6.1.2 was on the inactive partition on the CUCM server.
The partner came up with the idea that he would revert the CUCM servers to 6.1.2 and do the upgrade from there. What happened was that, although the migration worked, all of the configuration / db changes made to the system since the upgrade to 6.1.3 were lost (and the customer was unhappy)
It 'APPEARS' that when you revert a system to a previous version, the database from the current system is not copied back to the previous system image. Of course this make perfect sense (in hindsight) because there are likely to be db schema changes between versions that would be difficult to deal with during reversion.
My question is: Is this documented anywhere? Do we have a document I can give to the partner that details what exacty is preserved or what the caveats are to watch out for when reverting to an old version of CUCM (in the appliance model)? This does not appear to be covered in the install/upgrade docs.
Thanks for any help.