By Alex Zaballa
I was in a project where the customer had one database in a training environment to upgrade from 11g to 19c.
The customer requirement was to have a fallback option in case of any issue in the next few days.
The fallback option during the upgrade is to create a GUARANTEE RESTORE POINT. But after a few days, you can lose data in case you go back to the restore point.
To be honest, I have never seen a downgrade in all my Oracle life, but it was a customer requirement.
And yes, we are not touching the COMPATIBLE parameter after the upgrade 🙂
We did the upgrade to 19c using AutoUpgrade and everything works great.
But, when we decided to test the catdwgrd.sql, we had a lot of ora-600 at the end of the downgrade process.
Then, I found something that I was not aware of: A document called “Required Task to Preserve Downgrade Capability”.
Where you have some patches to apply on 11g:
Also, make sure you are taking care of the Timezone, especially updating Timezone files in the 11g home.
Fonte: Alex Zaballa