Based on the information provided, this environment would be considered a "A proof-of-concept for a small business":
* Depolyment size: Small
* Recommended Number of Hubs: 1 (Primary Hub)
* Recommended Number of Robots: 100 or less
Reviewing our documentation futher for upgrading an existing environment to Secure Hub and Robot, if your primary hub is not a tunnel server or tunnel client, the 9.2.0 upgrade installer converts your primary hub into a tunnel server (when the secure option is used). Although no other hubs are running in this environment, the Primary Hub will be automatically upgraded to a Tunnel Server. The installer also converts other hubs that are pointing to that primary hub into tunnel clients and in this case, no other hubs are present.
Note: As this scenario is not documented nor tested, we are making an assumption that the deployment of the HUB 9.20S to the Primary Hub, will require or result in the Primary Hub becoming a Tunnel Server.
It is not ideal to have a primary hub as a tunnel server, it might be useful in very small environments or for demonstrating proof of concepts (PoCs). However, in production environments, it is recommended that you always make your primary hub as a tunnel client. Before making any changes within this environment, we would highly recommend a conversation with the end client to determine future deployment plans using UIM / DX IM. As this may lead to migration/upgrade problems in the future which will require a paid services engagement from our partner.
If you plan to continue with this environment and procedure, our recommendation would be to install a Secondary hub server and follow the steps outlined in the Manually Upgrade to Secure Hub and Robot, Upgrade Process documentation: https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/it-operations-management/unified-infrastructure-management/9-0-2/upgrading/ca-uim-upgrade-step-3-deploy-the-upgrade/upgrade-uim-server/secure-hub-and-robot-ca-uim-9-sp1/manually-upgrade-to-secure-hub-and-robot.html#concept.dita_684db17791b8164bbf5aa7608fd5870502e664e1_23UpgradeProcess
High Level Overview of recommended actions:
1. Deploy a NEW Secondary Hub within this environment.
2. Ensure the "Considerations" and "Prerequisites" have been met. https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/it-operations-management/unified-infrastructure-management/9-0-2/upgrading/ca-uim-upgrade-step-3-deploy-the-upgrade/upgrade-uim-server/secure-hub-and-robot-ca-uim-9-sp1/manually-upgrade-to-secure-hub-and-robot.html
3. Follow Steps 1 to 9 of the "Upgrade Process". https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/it-operations-management/unified-infrastructure-management/9-0-2/upgrading/ca-uim-upgrade-step-3-deploy-the-upgrade/upgrade-uim-server/secure-hub-and-robot-ca-uim-9-sp1/manually-upgrade-to-secure-hub-and-robot.html#concept.dita_684db17791b8164bbf5aa7608fd5870502e664e1_23UpgradeProcess