Per our documentation:
We support the latest version of RHEL 7.x unless otherwise specified.
This release introduces support for the following operating systems:
The page also lists verified releases.
So RHEL 7.7 would is supported but not verified.
Vertica's DB statement
When there are multiple minor versions supported for a major operating system release, Micro Focus recommends that you run Vertica on the latest minor version listed in the supported versions list.
For example, if you run Vertica on a Red Hat Enterprise Linux 7.x release, Micro Focus recommends you upgrade to or be running the latest supported RHEL 7.x release.
If any functionality of CA PM doesn't work on the latest RHEL release then you shouldn't ask us to downgrade which is not possible here. Can you confirm?. If not, then how we supposed to upgrade our servers to the latest RHEL?.
The point that I wanted to make here is you can run the Product on the latest release however if there is a defect and that is due to the OS then we might have to ask you to move to a latest supported release as per the document.
Note: From a support perspective, we cannot give confirmation to go-ahead however as mentioned above its the customers call to go ahead and
upgrade to the latest release of RHEL and will support it but in case Engineering thinks that a problem is due to the version of OS then we might ask you to move to a certified release however the recommendation from our side is to be on the latest supported release as per documentation.
You can always reach out to your account management team to get the issue escalated to product management for review.