Installing an On Premise Monitoring Station (OPMS) on RHEL requires access to the rhel-7-server-optional-rpms and rhel-7-server-extras-rpms repositories as documented here:
Can we install an OPMS on Red Hat without installing the Network Manager package?
The Network Manager package on RHEL is needed for installation and upgrades only. This package is used to install specific repositories (and verify dependencies on repositories the installer needs to run). Once the OPMS is installed, Network Manager can be disabled. However, for future upgrades, this package will need to be enabled again.
As always, please contact CA Technologies support if you have further questions.