Ciao Giacomo,
My suspicion is that the 150MB backup does not include time series (historically performance) data. If your daily archive is 400MB, then I'd expect a full backup to be at least 400MB*7 = 2.8GB for time series data.
If you have archive data, you must be doing a 7.3.0 to 7.3.1 upgrade, as archive data didn't exist until 7.3.0.
General recommendations for understanding what OCI upgrades/restores are doing:
..\sanscreen\bin\log -> What files are being written to? When were they last being written to?
..\SANscreen\wildfly\standalone\log -> On 7.3.x , this is the folder where WIldFly logs to. If an OCI install has gotten far enough along, the "SANscreen Server" service is up and running, and logs get created and updated in this folder.
Upgrade.log is what you want to look at to see where the database/data restores are.
Task Manager - is anything driving substantial CPU? The MySQL portion of OCI restores/upgrades tends to peg one CPU core.
Resource Monitor -> Disk activity -> Where is disk IO occurring?