When upgrading to 9.3.x, you might observe that logs are no longer rotated. This issue is resolved in 9.3.1-3. If you experience this issue, consider upgrading to 9.3.1-3 and later. For more information, see 9.3.x Release Notes.
I had this issue few days ago, I found all upgraded databases (9.2 to 9.3) had huge vertica.log.
It had caused to use more disk space so my data retention job delete old data.
Finally i found this was because of removing python (2.7) on vertica 9.3! But Crontab is still configured with python path (not python3).
So i changed it to python3 path and it worked